Ministry of Agriculture & Rural Development Project Progress Report 029/05VIE: Implementation of the IPM program using weaver ants as a major component for cashew growers in Vietnam MS7: Research/technical Report Renkang Peng, Keith Christian, La Pham Lan and Nguyen Thanh Binh 31 July 2008 1 Institute Information Project Name Implementation of the IPM program using weaver ants as a major component for cashew growers in Vietnam Vietnamese Institution Institute of Agricultural Science of South Vietnam Vietnamese Project Team Leader Mr La Pham Lan Australian Organisation Charles Darwin University Australian Personnel Prof Keith Christian and Dr Renkang Peng Date commenced February 2006 Completion date (original) January 2009 Completion date (revised) Reporting period July 2008 Contact Officer(s) In Australia: Team Leader Keith Christian Name: Professor Position: Organisation Charles Darwin University Telephone: Fax: Email: 61 89466706 61 89466847 keith.christian@cdu.edu.au In Australia: Administrative contact Jenny Carter Name: Research Manager Position: Organisation Charles Darwin University Telephone: Fax: Email: 61 08 89466708 61 89467199 jenny.carter@cdu.edu.au In Vietnam La Pham Lan Head of Plant Protection Department Organisation Institute of Agricultural Science of South Vietnam Name: Position: Telephone: Fax: 84 0913829560 84 8297650 Email: lphlan@yahoo.com Summary To assist our cashew IPM TOT training program, field experiments, field surveys and observations, laboratory experiments and rearing were conducted in Binh Phuoc, Dong Nai and Dak Lac provinces between July 2006 and March 2008 Data obtained from the field experiments and field surveys showed that • The common insect pests damaging flushing terminals, cashew apples and/or nuts were tea mosquito bugs, shoot borers, coreid bugs, thrips, apple-nut borers, leaf rollers, leaf miners, aphids and mealy bugs, among which tea mosquito bugs, shoot borers, leaf rollers and apple-nut borers were the major pests during the flowering and fruiting period The branch borer and the stemroot borer were the major pests damaging branches and trunks • Weaver ants were similar to insecticides for controlling a range of insect pests, such as tea mosquito bugs, shoot borers, apple-nut borers, leaf rollers and leaf miners • Cashew yields were similar between the IPM plot and the farmer’s plot, but nut quality was higher in the IPM plot than in the farmer’s plot because of the foraging behaviour of weaver ants • Mealy bugs and aphids, that are currently determined to be minor pests, were unlikely to become major ones after the main pests are controlled by weaver ants A total of 12 species of natural enemies of aphids and species of natural enemies of mealy bugs were determined, and these natural enemies were more frequently seen in the IPM plot than in the farmer’s plot, showing that when weaver ants were present, mealy bugs and aphids were present, and predators and parasitoids of these pests were also present, resulting in very little damage to the cashew crop • The key to successfully manage the IPM plot was to keep weaver ant populations high and stable The boundary fighting between weaver ant colonies and the competition between weaver ants and other ant species were determined to be very important for the reduction of weaver ant populations Solutions for these competitive interactions were provided and discussed Data obtained from field observations, laboratory experiments and rearing showed that • A soft chemical (Abamectine) was effective in controlling thrips, on which weaver ants have a little effect, and it was not harmful to weaver ants • The bio-ecology of the branch borer and the stem-root borer were extensively studied Based on their ovipositing behaviour, initial damage symptoms and their life cycles, an integrated management strategy for each of the pests was recommended These strategies include three components (monitoring, removal of young larvae based on initial damage symptoms, and chemical injection) • Control strategies developed for thrips, branch borers and stem-root borers are compatible with the other components of the cashew IPM program Based on the above results and general farming practice, a cashew IPM program which is suitable for cashew growing conditions in Vietnam has been developed and is described in Appendix Introduction To assist our cashew IPM TOT training program, field experiments, field surveys and observations, laboratory experiments and rearing were conducted in Binh Phuoc, Dong Nai and Dak Lac provinces (the three biggest cashew growing provinces in Vietnam) between July 2006 and March 2008 The field experiments were conducted in three demonstration orchards, each of which was divided into two plots: a farmer’s plot that was managed with chemical insecticides, and an IPM plot that was managed by using the weaver ants (Oecophylla smaragdina) The field surveys were also conducted in three orchards at different time of the cashew developmental stage At each orchard, the main insect pest damage was assessed in tree groups: trees with weaver ants, trees with other species of ants, and trees without ants The objectives of the field experiments and surveys were: (1) letting TOT trainees observe and assess the main cashew insect pests and diseases (morphs, damage symptoms and life history) and their natural enemies at different cashew developmental periods, and make comparisons between the farmer’s plot and the IPM plot, (2) letting TOT trainees assess the effective control of the main insect pests by the most important bio-control agent - weaver ants, (3) demonstrating how to use weaver ant colonies properly in cashew orchards, (4) demonstrating how to use different farming strategies at the different periods of the year to grow healthy cashews, and (5) collecting technical data to comprise the cashew IPM curriculum and the cashew IPM photo book This report will summarise the effectiveness of weaver ants in controlling the main cashew insect pests, which directly damage flushing terminals, apples and nuts, and their effect on cashew yield and nut quality through comparisons between the farmer managed plots and the IPM plots and between trees with weaver ants and trees without the ants The following problems have been addressed during this period of the project: (1) The branch borer (Rhytidodera integra) and the stem-root borer (Plocaederus obesus) larvae cause the damage inside branches and the trunk, often resulting in the death of main branches or even the whole tree Our preliminary observations revealed that although weaver ants can catch or repel some adults from trees, they have no ability to control the larvae when they bore into branch or tree trunk In order to develop control methods that can manage the pests without negative effect on weaver ants, the bio-ecology for each of these two pests in southern Vietnam is needed However, no such information is available (2) Thrips (Rhynchothrips sp and Scirtothrips dorsalis) that damage cashew flowers, apples and nuts are not the main pests in insecticide control orchards because insecticides used to control tea mosquito bugs (Helopeltis antonii and H theivora), shoot borers (Alcidodes sp) and flower caterpillars also control thrips However, the use of weaver ants is incompatible with the use of toxic insecticides Thrips damage on apples and nuts is increasing in some areas Weaver ants can reduce the thrips populations, but they cannot reduce the thrips damage below the economic injury level Therefore, it is necessary to find locally available low toxic insecticides that are effective in controlling the thrips, but that are not harmful to weaver ants (3) Weaver ants have a mutual relationship with aphids (Toxoptera sp and Aphis gossypii) and mealy bugs (Dysmicoccus brevipes and Ferrisia virgata), many cashew growers are concerned about whether these minor insect pests will become major ones after the weaver ant is used The results from our research in different cashew growing regions show that aphids and mealy bugs in cashew orchards with weaver ants are unlikely to become major insect pests Their populations can be naturally reduced by their natural enemies on which weaver ants have limited effect To demonstrate this relationship for TOT trainers and cashew farmers, apart from our regular monitoring on these pests between the farmer’s plot and the IPM plot at our demonstration orchards, determination of natural enemy species of aphids and mealy bugs in cashew orchards is important This work has never been done in Vietnam Extensive field observations, laboratory experiments and rearing were conducted in Hong Loc Centre to understand the behaviour and the life cycle of the branch borer and the stem-root borer, to select locally available soft chemicals to control thrips, and to determine natural enemy species of aphids and mealy bugs The results from this work will also be summarised in this report together with a discussion of how the suggested control methods of these pests fit the cashew IPM program, which uses weaver ants as a major component Materials and methods Field experiments Three long-term field experiments were conducted in three demonstration orchards: Mr Ty’s orchard in Dong Phu District of Binh Phuoc province, Hong Loc Centre orchard, and Mr Bi’s orchard in Trang Bom District of Dong Nai province Mr Ty’s orchard This orchard has about of cashew trees grown from seeds To limit the effect of soil nutrition, half of this orchard was equally divided into two plots across the slight slope: farmer’s plot (70 trees) and IPM plot (70 trees) Around the IPM plot, a row of cashew trees was used as a buffer zone For insect pest control, chemical insecticides were used in the farmer’s plot, and sprays were done by the orchard owner based on his own experience In the IPM plot, weaver ants were used, and they were managed by an experimentalist The other farming activities, such as weeding, pruning, fertilizer application and the use of fungicides, were done the same for the farmer’s plot and the IPM plot and were conducted by the orchard owner Due to regular insecticide use, this orchard had no weaver ants before it was used as our demonstration orchard To establish and manage weaver ant colonies in the IPM plot, the following steps were followed: (1) the dominant ant species in each tree of the plot was determined We found all the trees were fully occupied by the crazy ant (Anoplolepis gracilipes), which is a competitor with weaver ants; (2) to reduce the crazy ant populations, a contact-killing insecticide (Motox ®) was sprayed at the tree bases while fallen leaves were raked to expose the ant nests; (3) a week later, about - 10 trees were grouped together with twisted polystrings if their side branches were not attached in preparation for receiving new weaver ant colonies Due to the fighting behaviour of weaver ants between colonies, each group of trees received only one colony; (4) a total of 10 weaver ant colonies were transplanted to the trees at a rate of – nests /tree in November 2006; and (5) fresh minced fish meat was provided to each ant colony during the period of tree dormancy Two weeks later and onwards after weaver ant colonies were transplanted, all the ant colonies were regularly monitored Weaver ant abundance was expressed as a percent per tree by the following method: (the number of main branches with a weaver ant trail in a tree / the number of the main branches in the tree) x 100 Weaver ants on a tree were treated as “Abundant”, if > 50% of the main branches had ant trails The major insect pest damage between the two plots was regularly monitored The damage symptoms for each of the major insect pests on flushing shoots, flowers and nut was easily recognized and separated in the field by experimentalists who were preliminarily trained with such knowledge All the trees in each plot were numbered in sequence Two-weekly monitoring occasions were also numbered in sequence In each plot, trees with odd numbers were inspected in odd numbered weeks, and trees with even numbers were inspected in even numbered weeks, so that freshly damaged shoots would not be repeatedly counted (because soft foliar or floral flushes were hardened before the next monitoring occasion) Preliminary observations suggested that all the main insect pests were more active in the lower tree canopy than in upper levels Therefore, the monitoring was concentrated in the lower level of the tree canopy For each tree, we recorded the total number of flushing shoots (including foliar or/and floral flushing terminals) and the number of freshly damaged shoots by each major pest, and percent damage was calculated The cashew yields were measured in each plot one week before harvest by the following formula: total numbers of nuts counted on the half canopy of each tree on the same side × canopy score Four canopy scores (1, 1.33, and 4) were used based on the size and thickness of each tree canopy: score = ‘1’, if the canopy was 100% goodness (the canopy being biggest and thickest); score = ‘1.33’, if the canopy was 75% goodness; score = ‘2’, if the canopy was 50% goodness; score = ‘4’, if the canopy was 25% goodness Cashew nut quality was generally assessed on site based on overall nut appearance: shine and clean skin Hong Loc Centre orchard The orchard is next to Dong Nai TOT training Centre, which is very convenient for TOT trainees to field experiments and observations The orchard had ten cultivars, each of which occupied one row, and each row was divided into two parts (farmer’s part and IPM part) A total of 10 farmer’s parts made a farmer’s plot, with 67 trees A total of 10 IPM parts made an IPM plot, with 71 trees There were 14 existing weaver ant colonies randomly distributed in this orchard In the farmer’s plot, weaver ants on most of the trees were manually removed to the trees without weaver ants in the IPM plot, and then chemical insecticides were used to remove the remaining ants to make sure no weaver ants were in the farmer’s plot In the IPM plot, after existing weaver ant colonies were combined with the transplants from the farmer’s plot, almost every tree had weaver ants Apart from weaver ants, we also found ghost ants (Tapinoma melanocephalum), small sized crematogaster ants (Crematogaster sp) and an unidentified black ant in this orchard, but we did not bait them because they were not found to compete with weaver ants The experiment began in September 2007 The field management, weaver ant monitoring, insect pest monitoring, and yield, and nut quality assessment followed the same protocol as Mr Ty’s orchard (see above) Mr Bi’s orchard This orchard has two blocks next to each other, and each block is about one Block was used from September 2006 to July 2007, and because of the disturbance of the site caused by the owner, block was used from September 2007 to May 2008 In each block, 120 cashew trees of the same cultivar and similar size were used, and they were divided into two plots (farmer’s plot – 60 trees and IPM plot – 60 trees) Due to regular insecticide use, cashew trees in this orchard had no weaver ants, but they were occupied by mud-nesting crematogaster ants (Crematogaster sp), ghost ants and an unidentified black ant In 2006, to establish weaver ant colonies in the IPM plot, these ant species were baited by an ant bait (fresh minced fish meat mixed with Regent®) A week after baiting, these ant populations were greatly reduced, and weaver ant colonies were transplanted into the IPM plot in early December 2006 The field experimental design, field management, weaver ant monitoring, insect pest monitoring and yield assessment followed the same protocol as Mr Ty’s orchard (see above) Surprising results were obtained from December 2006 to July 2007, showing lower cashew yield and nut quality and heavier pest damage on foliar and floral shoots in the IPM plot compared to the farmer’s plot Through a detailed examination in April 2007, the following phenomenon was observed: (1) boundary fighting between weaver ant colonies and weaver ants dispersal to orchard boundary trees resulting in 30% of the trees being without weaver ants, and 30% of the trees had very low numbers of weaver ants (the ant abundance being < 30%) These trees were either fully or partly occupied by ghost ants, and they were heavily damaged by tea mosquito bugs, shoot borers and fruit-nut borers (2) on the remaining 40% of the trees, weaver ants were abundant on tree trunks and the main branches, but they did not forage on aphid-free foliar and floral shoots, resulting in the heavy damage on flushing shoots, flowers and developing nuts by tea mosquito bugs, shoot borers and fruit-nut borers The first phenomenon was mainly due to the experimentalist who lacked the experience in managing weaver ant colonies Ghost ants are very small (about 1.1 mm), and they were incorrectly thought not to be very competitive with weaver ants For the second phenomenon, field surveys were conducted in different types of cashew orchards with weaver ants together with interviews of the orchard owners for information about farming practice Through comparisons, it seemed that heavy leaf fertilizer sprays (3 applications done in the IPM plot between December 2006 and January 2007) may suppress or change the level of extra floral nectar secreted by flushing terminals, which made them unattractive to weaver ants In 2007, therefore, more attention was paid to weaver ant colony management and no leaf fertilizers were used in the IPM plot The other management, such as baiting other ant species, weaver ant transplantation, weaver ant monitoring, insect pest monitoring and yield assessment, followed the same protocol as in the first year Field survey A total of field surveys were done in three cashew orchards: Mr Quang’s orchard in Dong Xoai district of Binh Phuoc province, Mr Be’s orchard and Mr Sau’s orchard in Trang Bom District of Dong Nai province Mr Quang’s orchard This orchard had 60 cashew trees grown from seeds (14 trees over 10 years old and 46 trees about years old) This orchard was surrounded by two patches of mahogany trees and cassava crop Because no insecticides were used, there were three existing weaver ant colonies on big cashew trees and mahogany trees, and the ants had dispersed to some of the young cashew trees when we did the first survey in July 2006 As big cashew trees were too tall to make an accurate assessment of the main pest damage, each survey was concentrated on the 46 small trees On each survey, all the 46 trees were inspected, and for each tree, we recorded the dominant ant species on the tree, the total numbers of flushing foliar and/or floral terminals on the tree and the number of terminals damaged by each major pest, and the percentage damage was calculated A total of three surveys were done in this orchard: July 2006, December 2006 and April 2007 Mr Be’s orchard Two surveys were done in this orchard which has several blocks of cashews The first survey was conducted in July 2006 in a block of about In this block, trees were over 20 years old, but there were 18 young trees (about three years old) randomly growing among the big trees due to the replacement of the dead trees Insecticides were not regularly used in this block (about one or two times a year), and therefore, there were some existing weaver ant colonies on big trees, and they had dispersed to some of the young trees Because big cashew trees were too tall to make assessment of the main pest damage, this survey was concentrated on the 18 small trees The second survey was conducted in another block of the orchard in August 2007 in collaboration with a field practical of the TOT training This block was about one ha, and trees were years old of similar size This block was closely surrounded by old cashew trees (> 10 years) There were several weaver ant colonies on the big trees, and they had dispersed to some of the young trees A total of 50 young trees were surveyed For each survey, the methods used were the same as in Mr Quang’ orchard Mr Sau’s orchard This is an abandoned orchard, and it had 53 medium sized cashew trees of unknown age There were three existing weaver ant colonies: one in the orchard, and another two colonies originally on the Eucalyptus trees on the edge of the orchard, which had dispersed to a few cashew trees A survey was done in July 2006 The survey methods used were the same as in Mr Quang’ orchard Field observations and laboratory rearing Field observations and laboratory rearing were conducted in Hong Loc centre, Hong Loc Centre orchard, Mr Sau’s orchard and some orchards in Dak Lac province The observations concentrated on the bio-ecology of the branch borer and the stem-root borer, including the behaviour of larvae and their life cycle This was done by dissecting branches and stems at different cashew developmental periods The adult emergence, activity and oviposition were also observed in evenings The laboratory rearing was concentrated on natural enemy species of aphids, mealy bugs and shoot borers In order to find a suitable soft chemical that will reduce thrips populations on developing nuts, but will not be harmful to weaver ants, lab experiments were conducted using the locally available soft chemicals using four treatments: developing nuts and apples with thrips were treated with Applaud, D.C Tron oils, Abamectine and water, respectively Data analysis For field experimental data analyses, on each monitoring occasion, two plots (farmer and IPM) were ranked, based on mean percentage damage by each major pest All the monitoring occasions in the flowering and fruiting period and in the dormant or leaf flushing period were separately compared by a non-parametric Friedman 2-way ANOVA by ranks using SYSTAT statistics software The percentage yield data and field survey data were analysed by a Kruskal-Wallis one-way ANOVA by ranks to test for a difference between plots and between trees with or without weaver ants Results Field experiments Mr Ty’s orchard % Weaver ant abundance The weaver ant populations in the IPM plot were high and stable from December 2006 to July 2007, and the average ant abundance was over 80% (Fig 1) However, from August 2007 to January 2008, the ant populations gradually decreased from 70% to 28% (Fig 1) This was mainly due to fighting between weaver ant colonies 140 120 100 80 60 40 20 23 Jan 31 Jan 23 23 Feb Feb Mar Mar Apr Apr 23 23 Apr May May Jun 23 Jul 14 24 Jun Nov Dec Jan 12 Jan | -2007 | -2008 | Fig Average weaver ant abundance in the IPM plot at Binh Phuoc province, Vietnam Although the numbers of flushing terminals per tree were higher in the IPM plot than in the farmer’s plot, the difference between the two treatments was statistically similar (P > 0.05; Table 1) Table The average number of flushing shoots per tree for the farmer’s plot and the IPM plot during the period of pre-flowering flush and nut development (November – March), Binh Phuoc province, Vietnam Plot Mean number of shoots Rank sum /tree + SD Farmer 86.6 + 28.3 12.0 IPM 102.3 + 39.7 18.0 Friedman two–way ANOVA Xr2 =3.600; df = 1; P = 0.058 Based on the monitoring data, the common insect pests in this orchard were tea mosquito bugs, shoot borers, leaf miners (Acrocercops syngramma), aphids, the apple-nut borer (Nephopteryx sp), leaf rollers and branch borer The population fluctuations in the IPM plot and the farmer’s plot for tea mosquito bugs, shoot borers, leaf miners and aphids, are shown in Figs 2, 3, 4, and 5, respectively 10 bugs, shoot borers, leaf miners, aphids and leaf rollers was similar between the farmer’s plot and the IPM plot (P > 0.05; Figs 2-5; Table 2) However, the average level of developmental nuts damaged by the fruit-nut borer was lower in the IPM plot than in the farmer’s plot (P = 0.018; Table 2) Table The mean % shoots damaged by insect pests in the farmer’s plot and the IPM plot of the demonstration orchard at Binh Phuoc province, Vietnam Friedman two–way ANOVA Pest name Treatment Mean % shoots damaged /tree + SD Rank sum Statistic Tea mosquito bugs Shoot borers Farmer 6.5 + 3.8 IPM 6.7 + 3.2 Farmer 8.3 + 7.0 IPM 7.9 + 5.1 The leaf miner Farmer 1.8 + 1.6 IPM 1.8 + 1.5 Aphids Farmer 11.5 + 11.9 IPM 12.4 + 11.8 The fruit-nut Farmer 0.11 + 0.69 borer* IPM 0.01 + 0.15 Leaf rollers* Farmer 0.4 + 1.2 IPM 0.7 + 3.4 *, Mann-Whitney U test is used 14.0 16.0 14.0 16.0 15.5 14.5 14.5 15.5 57608.0 56395.0 56575.5 57427.5 Xr2 = 0.400; df = 1; P = 0.527 Xr2 = 0.400; df = 1; P = 0.527 Xr2 = 0.111; df = 1; P = 0.739 Xr2 = 0.111; df = 1; P = 0.739 U = 29405.0; df = 1; P = 0.018 U = 28372.5; df = 1; P = 0.933 During the cashew dormant or leaf flush period (April to July), the damage on flushing shoots by tea mosquito bugs, shoot borers and leaf miners was significantly lower in the IPM plot than in the farmer’s plot (Figs 2-4; Table 3) However, the average level of shoots with aphids was more in the IPM plot than in the farmer’s plot (Fig 5; Table 3) Table The mean % shoots damaged by insect pests in the farmer’s plot and the IPM plot during the tree dormancy or leaf flush period at Binh Phuoc province, Vietnam Friedman two–way ANOVA Pest name Treatment Mean % shoots damaged /tree + SD Rank sum Statistic Tea mosquito bugs Shoot borers The leaf miner Aphids Farmer IPM Farmer IPM Farmer IPM Farmer IPM 6.5 + 11.2 2.4 + 4.3 5.0 + 2.0 2.4 + 0.9 1.2 + 1.0 0.5 + 0.3 9.0 + 5.9 13.3 + 9.6 16.0 8.0 16.0 8.0 15.0 9.0 8.0 16.0 Xr2 = 8.000; df = 1; P = 0.005 Xr2 = 8.000; df = 1; P = 0.005 Xr2 = 4.500; df = 1; P = 0.034 Xr2 = 8.000; df = 1; P = 0.005 In 2007, we missed the opportunity to assess the number of nuts on tree canopies before harvest However, after the harvest, the orchard owner told us that the nuts produced were cleaner and shinier in the IPM plot than in the farmer’s plot In 2008, the assessment of the number of nuts on tree canopies was done one week before harvest, and it showed that the number of nuts per tree was significantly 12 higher in the farmer’s plot than in the IPM plot (Table 4) Based on regular monitoring, we found that weaver ant populations in the IPM plot were very low (from 48% in December 2007 to 28% in January 2008; Fig 1), and the trees with low numbers of ants were heavily damaged by tea mosquito bugs and shoot borers during the flowering and fruiting time However, there were 20 trees which had reasonable numbers of weaver ants (the ant abundance was > 35%), and these were much less damaged by these pests When comparing the 20 trees in the IPM plot with the 70 trees in the farmer’s plot, there was no significant difference in the numbers of nuts per tree (Table 5) Table The average number of cashew nuts per half canopy in the farmer’s plot and the IPM plot of the demonstration orchard at Binh Phouc province, Vietnam Plot (Treatment) Mean number of nuts Number of Rank sum /tree + SD trees Farmer (use insecticides) 558.3 + 380.3 70 5482.5 IPM (use weaver ants only) 431.5 + 336.3 70 4387.5 Mann-Whitney U test U = 2997.5; df = 1; P = 0.022 Table The average number of cashew nuts per half canopy in the farmer’s plot and the IPM plot of the demonstration orchard at Binh Phouc province, Vietnam Plot (Treatment) Mean number of nuts Number of Rank sum /tree + SD trees Farmer (use insecticides) 558.3 + 380.3 70 3200 IPM (use weaver ants only) 526.9 + 332.3 20 894 Mann-Whitney U test U = 7150500; df = 1; P = 0.880 Hong Loc Centre orchard Fig Average abundance of weaver ants in the IPM plot at Hong Loc Centre, Dong Nai province, Vietnam % weaverv ant abundance Fig shows that weaver ant abundance was over 60%, and the ant populations were stable during the period of cashew flowering and fruiting (December 2007 – February 2008) 120 100 80 60 40 20 22 Dec 07 Jan 08 19 Jan 08 Feb 08 16 Feb 08 The average number of flushing shoots was more in the IPM plot than in the farmer’s plot, but they were not statistically different (Table 6) 13 Table The average number of shoots per tree in the farmer’s plot and the IPM plot of the demonstration orchard at Hong Loc Centre, Dong Nai province, Vietnam Rank sum Plot (Treatment) Mean number of shoots /tree + SD Farmer (use insecticides) 29.9 + 10.2 IPM (use weaver ants only) 36.4 + 15.4 Friedman two–way ANOVA Xr2 = 3.000; df = 1; P = 0.083 Based on regular monitoring, the main insect pests in this orchard are tea mosquito bugs, leaf rollers, leaf miners, aphids and branch borers The minor pests are shoot borers and mealy bugs The mean damage level on cashew flowers and young nuts by each of these pests was similar between the farmer’s plot and the IPM plot (Table 7) In a field observation, a branch borer adult was chased away by weaver ants from a mature shoot (branch borer preferred oviposition location) Table The mean % shoots damaged by insect pests in the farmer’s plot and the IPM plot of the demonstration orchard at Hong Loc Centre, Dong Nai province, Vietnam Friedman two–way ANOVA Pest name Treatment Mean % shoots damaged /tree + SD Rank sum Statistic Tea mosquito bugs The shoot borer* Leaf rollers Farmer 1.25 + 2.64 IPM 2.49 + 3.40 Farmer 0.64 + 1.79 IPM 0.26 + 1.06 Farmer 3.13 + 3.85 IPM 3.42 + 3.93 The leaf miner Farmer 2.75 + 3.83 IPM 2.65 + 4.49 Mealy bugs* Farmer 0.69 + 2.03 IPM 1.96 + 5.49 Aphids Farmer 0.75 + 2.47 IPM 1.96 + 4.33 *, Mann-Whitney U test is used 5273.5 5166.5 4780.5 5659.5 6.5 8.5 Xr2 = 3.000; df = 1; P = 0.083 U = 2788.5; df = 1; P = 0.135 Xr2 = 0.333; df = 1; P = 0.564 Xr2 = 2.000; df = 1; P = 0.157 U = 2295.5; df = 1; P = 0.088 Xr2 = 1.000; df = 1; P = 0.317 The average number of nuts per tree were similar between the farmer’s plot and the IPM plot (P = 0.206; Table 8) The nuts were cleaner and shinier in the IPM plot than in the farmer’s plot Table The number of cashew nuts per half canopy in the farmer’s plot and the IPM plot of the demonstration orchard at Hong Loc Centre, Dong Nai, Vietnam Plot (Treatment) Mean number of nuts /tree Rank sum + SD Farmer (use insecticides) 179.2 + 104.7 17 IPM (use weaver ants only) 177.9 + 143.9 13 Friedman two–way ANOVA Xr2 = 1.600; df = 1; P = 0.206 Mr Bi’s orchard 14 The regular pest monitoring showed that the common insect pests in this orchard were tea mosquito bugs, shoot borers, leaf miners, leaf rollers, thrips, aphids, fruit-nut borers and branch borers The general farming practice of this orchard was very well managed; farmer’s and IPM plots were free from any weeds (two applications of herbicide spray and one time manual weeding each year) and applications of insecticide sprays per year were applied in the farmer’s plot during the pre-flowering time and nut developmental period (later October – early March) The results obtained from November 2006 to July 2007 are summarised below: (1) The average abundance of weaver ants was < 40% in the IPM plot, which was low, (2) during the period from pre-flowering flush to nut development (December – March), the average damage level for each of the main pests was greater in the IPM plot than in the farmer’s plot; and (3) the yield and nut quality was significantly lower in the IPM plot than in the farmer’s plot As of late January 2008, regular weaver ant and insect pest monitoring, together with field observations, showed that: (1) Weaver ant colonies were, in general, managed well, and the average abundance of the ants was > 50%, (2) Although trees did not receive any leaf fertilizer sprays, weaver ants were still abundant on tree trunks and the main branches, and they were rarely seen foraging on aphid-free foliar and floral shoots as observed last year, which resulted in over 50% of flushing shoots, flowers and developing nuts being damaged by tea mosquito bugs, shoot borers and leaf rollers and fruit-nut borers in the IPM plot, (3) Slight taps on the tree bases resulted in abnormal aggressive behaviour by the ants, (4) Competition between weaver ants and ghost ants for food was observed Ghost ants were originally thought to be too small (only 1.1 mm) to be effective competitors against weaver ants In fact, we found that on cashew trees, these ants only feed on extra floral nectar secreted by flushing shoots, flower panicles and young nuts They nest underground in complicated network systems with huge numbers of individuals They foraged actively and collectively in very large numbers on cashew tender terminals Cashew extra floral nectar is a preferred food for weaver ants In an observation, we observed that when a weaver ant fed on nectar of a tender flower shoot on which there were some ghost ants, it was attacked by several ghost ants, which grasped the legs, antenna and mandibles Two minutes later, two legs and two antenna of the weaver ant were cut off, resulting in the death of the ant Ghost ants did not eat or take the dead weaver ant back to their nest, but they let it drop down on the orchard floor Following this clue, we found quite a few dead weaver ants on the orchard floor During such encounters, some weaver ants acted quickly and escaped from ghost ant attack, but they were scared off flushing shoots, flowers and young nuts, resulting in the large numbers of weaver ants walking on tree trunks and branches in an aggressive posture (5) We also found that numbers of ghost ants went up and down, travelling over the tree trunk and branches where a lot of weaver ants were present, but they did not actively attack the weaver ants 15 Having determined this competition, we immediately took two actions; (1) to spray engine oil around each tree base to stop ghost ants coming up from the ground, and (2) to bait the ghost ants with fresh fish meat mixed with Regent® The engine oil was only effective for 12 hours The fish bait was very attractive to ghost ants, and their populations were greatly reduced in the first - days At the same time, however, the bait also attracted a lot of flies, and these flies died in a couple of hours and fell on the orchard floor or on the tree leaves Due to great reduction of ghost ants, weaver ants started to actively forage on flower terminals and tender leaf shoots We found that a lot of dead flies were carried by weaver ants to their nests As a result, the weaver ant populations were greatly reduced two days later, and a lot of weaver ants were found dead in their nests because of the poison from dead flies This led to a great reduction of weaver ant abundance from 65% to below 15% within a period of weeks Because of this, the average damage level of flushing terminals by each of the main pests was much higher in the IPM plot than in the farmer’s plot, and the yield and nut quality in 2008 were much lower in the IPM plot than in the farmer’s plot Field survey Mr Quang’s orchard Three surveys conducted in this orchards in 2006 and 2007 showed that shoot borers, tea mosquito bugs, leaf rollers and fruit-nut borer are the common pests (Table 9) The mean damage level by the common pests was between 0.8% and 8.6% on trees with weaver ants, but between 3.4% and 36.0% on trees without the ants (Table 9) This damage level for each of the pests at the different survey times was highly significant (Table 9) 16 Table The mean % flushing terminals or developmental nuts damaged by the main insect pests in trees with weaver ants (WA) and trees without the ants at Mr Thiem Truong Quang’s orchard, Dong Xoai, Binh Phuoc province, Vietnam Survey Pest Trees No of Mean % Mann-Whitney U test date name with trees damage /tree Rank sum Statistic + SD U = 455.5; df = July Shoot No WA 29 36.0 + 20.3 890.5 1; P < 0.001 2006 borers 190.5 WA 17 4.6 + 8.9 8.0 + 7.6 813.0 U = 378.0; df = Mosquito No WA 29 1; P = 0.002 bugs 268.0 WA 17 2.2 + 3.7 U = 280.5; df = Dec Shoot No WA 12 6.5 + 7.0 358.5 1; P = 0.025 2006 borers WA 33 2.3 + 3.4 676.5 Mosquito No WA 12 3.4 + 4.2 375.5 U = 297.5; df = bugs 1; P = 0.001 WA 33 0.3 + 1.1 659.5 U = 342.0; df = April Shoot No WA 19 18.2 + 15.7 532.0 1; P = 0.013 2007 borers 458.0 WA 25 8.6 + 12.0 Mosquito No WA 19 17.0 + 21.6 522.0 U = 332.0; df = bugs 1; P = 0.008 468.0 WA 25 2.5 + 6.8 U = 337.0; df = Leaf No WA 19 16.5 + 18.6 527.0 1; P = 0.014 rollers WA 25 5.3 + 8.7 463.0 U = 100.0; df = 16.4 + 20.6 145.0 Fruit-nut No WA 1; P = 0.016 borer WA 15 0.8 + 2.6 155.0 Mr Be’s orchard The common pests in this orchard were shoot borers, tea mosquito bugs and coreid bugs The mean damage level of flushing shoots for each of these pests was much lower on trees with weaver ants (< 5%) than on trees without weaver ants or with other species of ants (> 19%; Table 10) Table 10 The mean % flushing shoots damaged by the main insect pests in trees with and without weaver ants at Mr Be’s orchard, Dong Nai province, Vietnam Mann-Whitney U test Survey Pest Trees No Mean % date name with of damage /tree Rank sum Statistic trees + SD U = 79.0; df = July Shoot No WA 10 26.2 + 14.0 134.0 1; P < 0.001 2006 borers WA 0.9 + 1.4 37.0 U = 74.0; df = Mosquito No WA 10 24.3 + 17.2 129.0 1; P = 0.002 bugs WA 1.4 + 2.6 42.0 Aug The WA 15 4.3 + 4.0 154.0 H = 24.175; df 2007 coreid = 4; P < 0.001 Ghost ant 10 25.7 + 13.2 332.0 bug No ant 13 23.3 + 10.0 410.0 Cremat 19.6 + 8.3 107.0 Black ant 26.0 + 13.2 272.0 , WA = weaver ants; Cremat = Crematogaster sp , Kruskal-Wallis test was used Mr Sau’s orchard 17 The average damage level on flushing shoots by shoot borers and tea mosquito bugs was 2.4% and 1.4%, respectively, on trees with weaver ants, and these damage levels were significantly lower than those on trees without weaver ants (Table 11) Table 11 The mean % flushing shoots damaged by the main insect pests in trees with and without weaver ants at Mr Sau’s orchard, Dong Nai province, Vietnam Survey Pest Trees Mann-Whitney U test No Mean % date name with of damage /tree Rank sum Statistic trees + SD July Shoot No WA 45 8.3 + 8.2 1321.0 U = 286.0; df = 2006 borers 1; P = 0.008 WA 2.4 + 3.8 110.0 U = 302.0; df = Mosquito No WA 45 5.5 + 4.7 1337.0 1; P = 0.002 bugs WA 1.4 + 2.8 94.0 Field observations and laboratory rearing The Branch borer According to our field observations, the branch borer lived in cashew orchards throughout the year Eggs were laid singly predominantly at the tip of mature leaf shoots After hatching, a larva started to bore into the shoot, and fed on materials inside With feeding progress, the larva bore downward to the thick twig and branch, resulting in a hollow tunnel in the centre of the branch At a regular distance, the larva made a hole to the branch surface to get rid of the waste from the tunnel (Fig 7) The branch borer had only one generation per year Adults lived 20 + days, and they usually emerged between mid March and early June, and they were active in early evening The egg laying lasted 25 + days, which took place from April to July The initial damage symptom by young larvae was dark brown excreta sticking on the skin of a mature shoot (about 10 – 15 cm long from the tip; Fig 7), and these damaged shoots were mostly and easily seen on trees between July and August The development of the second instar larvae to a mature stage (which stops eating) was 270 + 10 days, which was from late April to January the following year Pupation took place in the branch and lasted 45 + days, which was from February to March The life cycle of the borer in a year is summarised in Table 12 Fig The excreta holes (7 holes circled in red) of a branch borer larva and the initial damage symptom A magnified hole after removal of excreta 18 Table 12 The life cycle of the branch borer in southern Vietnam Stage Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Adult | -| Egg | | Larvae -| | -Pupae | -| In a field survey at Mr Sau’s orchard in Dong Nai provinve, every tree was affected by the branch borer, but the damage symptoms were lower on trees with abundant weaver ants than trees without the ants In our evening observations, weaver ants chased a female branch borer from fresh shoots to a dry flower shoot The stem-root borer Our field observations showed that the stem-root borer lived in cashew orchards throughout the year, and it had only one generation per year The adults emerged between mid January and May, and they were active during evening for mating and ovipositing Adults prefer to oviposit • on old trees (> years old) that have thick bark with more cracks, • on wounded trees either caused by stem borers during the previous season or by physical actions like pruning, • in the cracks between the conjunctions of the trunk and the main branches and wounded places, and the most eggs were found within one meter from the ground Eggs are elongate in light yellow, and 4.1 mm long and 1.4 mm broad After hatching, the larvae bore through the inner bark and feed on sapwood, resulting in the small patch of exudation of a reddish brown liquid with some fine frass on the tree trunk between the tree base and up to one meter height (Fig 8) The newly hatched larva was about 3.5 mm long, which was easily removed (Fig 8), and grew up to about 58 mm long Later in the year (November to December), mature larvae bored into the heartwood at the tree base, and each larva excavated a chamber in which the calcareous pupal cell was formed from the excretions of the larva Pupation took place late in the year The pupa is about 35 mm long, creamy-white, robust and protected by the grey coloured cocoon The adult usually remains in the cocoon until January The life cycle of the stem-root borer is summarised in Table 13 Fig The initial damage symptoms of the stemroot borer on tree trunk 19 Trees over 10 years old are more infested than young trees In our field observations, a pupa in cocoon was parasited by a fungus Table 13 The life cycle of the stem-root borer in southern Vietnam Stage Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Adult | | Egg | | Larvae | | Pupae | | -Selection of soft chemicals to control thrips Two small scale experiments showed that Abamectine was more effective in controlling chilli thrips than Applaud and D.C Tron oils, and it did not show any effect on weaver ants two weeks after spraying Natural enemies of aphids and mealy bugs In our rearing trials, a total of 12 species of natural enemies of aphids and species of natural enemies of mealy bugs were determined (Table 14) These natural enemies were more frequently seen in the IPM plot than in the farmer’s plot at Hong Loc Centre orchard Table 14 The number of species of natural enemy reared from aphids and mealy bugs, Hong Loc Centre, Dong Nai province, Vietnam Aphids Mealy bugs Name of natural No of species Name of natural No of species enemy enemy Ladybirds Ladybirds Hoverflies Midge Lacewings Butterfly Parasitic wasp Parasitic wasp Dipteran fly 20 Discussion In cashew orchards, the common insect pests that damage flushing terminals, cashew apples and nuts were tea mosquito bugs, shoot borers, coreid bugs, apple-nut borers, leaf rollers, leaf miners, aphids and mealy bugs (Tables 2, 3, 7, 9, 10 and 11; Figs – 5) The major insect pests during the flower and fruiting periods were tea mosquito bugs, shoot borers, leaf rollers and apple-nut borers The common insect pests that fed on inside branches and stems were branch borers and stem-root borers Weaver ants are effective in controlling a range of common insect pests From field experiments in our demonstration orchards, weaver ants were similar to insecticides for controlling tea mosquito bugs, shoot borers, the apple-nut borer, leaf rollers, leaf miners and aphids during the flowering and fruiting periods (Tables and 7; Figs – 5) In field surveys, at different types of orchards, flushing terminals or nuts were significantly less damaged by tea mosquito bugs, shoot borers, leaf rollers, the applenut borer and coreid bugs on trees with weaver ants than on trees without the ants (Tables – 11) The branch borer was one of the main pests in the demonstration orchards, its damage in the two plots was not assessed This is because our monitoring was based on fresh damage on flushing terminals, but this pest damaged cashew trees by boring into mature terminals However, a field survey at Mr Sau’s orchard suggested that the damage symptoms were lower on trees with abundant weaver ants than trees without the ants Also, in our evening observations, weaver ants were observed chasing a female branch borer from mature shoots to a dry flower shoot This suggests that weaver ants can catch or deter some branch borer adults from trees Based on larvae damage behaviour and adult oviposition, to control this pest, some other methods will have to be used apart from weaver ants (see below) Weaver ants create higher quality nuts and similar yield compared to insecticides Due to the control efficiency of the insect pests by weaver ants, trees protected by the ants produced higher or similar numbers of flushing terminals than trees protected by insecticides (Tables and 6) With abundant weaver ants, the nut yield in the IPM plot was similar to the farmer’s plot (Tables and 8), but the nut quality was higher in the IPM plots than in the farmer’s plots The nuts were cleaner and shinier in the IPM plot than in the farmer’s plot This is because in the nut developmental stage, young nuts continuously secrete extrafloral nectar, particularly on the inside curve of nuts, which is a good food source for weaver ants With insecticide spray, the nectar is continuously deposited on the inside curve of nuts, resulting in a black residue on the nuts due to fungus invasion The nuts in the farmer’s plots have sooty mould, and look dull However, this nectar is continuously taken away by weaver ants, and thus, trees in the IPM plot produce clean and shining nuts Although we did not measure insecticide residue of nuts, the residue level should be much lower in nuts produced in IPM plots than those in farmer’s plots because no insecticides were used in the IPM plots Keeping weaver ant populations high and stable is a key for success in controlling insect pests and achieving high yield and nut quality In this study, two major factors responsible for the reduction of weaver ant populations were fights between weaver ant colonies and competition between weaver ants and other ant species Due to boundary fighting between weaver ant colonies, the ant abundance was greatly reduced from 80% in July 2007 to 28% in January 2008 at Mr Ty’s orchard (Fig 1), 21 resulting in the significant reduction of yield in the IPM plot (Table 4) However, in the IPM plot, there were 20 trees on which the ant abundance was > 35%, and the yield from these trees was similar to that in the farmer’s plot (Table 5) At Hong Loc Centre orchard, the ant populations were high (between 60% and 80%) and stable (Fig 6), which resulted in a yield similar to that produced by the farmer’s plot (Table 8) In contrast, at Mr Bi’s orchard in 2007, because of weaver ant boundary fights, the abundance of weaver ants was < 40% in the IPM plot, which was low The average damage level for each of the main pests was greater in the IPM plot than in the farmer’s plot, resulting in the significantly lower yield and nut quality compared to the farmer’s plot Also, in 2008 at the same orchard, due to the sideeffect of ghost ant baiting, weaver ant abundance was greatly reduced from 65% in early January to below 15% late January As a result, the main insect pest damage was much higher and the yield was much lower in the IPM plot than in the farmer’s plot A complete failure of insect pest control by weaver ants at Mr Bi’s orchard was due to the boundary fighting between weaver ant colonies and the strong competition between weaver ants and ghost ants in 2006 – 2007, and the strong competition between weaver ants and ghost ants in 2007 – 2008 With detailed instruction in the cashew IPM curriculum together with field practice, the boundary fighting between weaver ant colonies can be easily resolved Having followed this instruction, the experimentalist successfully managed weaver ant colonies in the block of Mr Bi’s orchard in 2007 - 2008 For the competition between weaver ants and ghost ants, we found that grass and weeds in orchards play an important role At Mr Bi’s orchard, the orchard owner kept this orchard cleared of any weeds, especially during the period of flowering and nut setting Therefore, apart from cashew trees, no other plants could be used by ghost ants In order to survive, they were forced to forage on cashew trees, resulting in the serious fighting with weaver ants for food However, at Hong Loc Centre orchard, which is 25 km away from Mr Bi’s orchard, ghost ants were commonly seen in the IPM plot, but no such competition was observed Weaver ants foraged on flower panicles and young nuts actively and peacefully Ghost ants were hardly seen on trees with abundant weaver ants, but actively foraged on weeds, grass and cashew coppice, which were kept at about 30 – 40 cm high, between tree rows This suggested that weeds provided alternative food source for ghost ants Therefore, to use weaver ants in cashew orchards, especially in the areas with abundant ghost ants, weeds should be kept at around 30 – 40 cm height, and they should be managed by mechanically cutting, but not by herbicides Minor pests like mealy bugs and aphids are unlikely to become the main pests after weaver ants are used in cashew orchards It is well known that weaver ants have a mutual relationship with some homopteran pests, such as mealy bugs, aphids and scales This is because scales, mealy bugs and aphids contain sugar in their excreta, and this is desirable food for weaver ants To get a rich sugar solution, weaver ants farm these insects Therefore, whether mealy bugs and aphids, that are currently considered minor pests in cashew orchards, will become major ones after the main pests are controlled by weaver ants is a major concern Our regular monitoring demonstrated that the average level of flushing terminals with aphids or mealy bugs was similar between the IPM plot and the farmer’s plot at Mr Ty’s orchard and the Hong Loc Centre orchard during the period of flowering and fruiting (Tables and 7) In the field observations and lab rearing, at least 20 species of predators and parasitoids were found to feed on or parasitise aphids and mealy bugs (Table 14) This 22 demonstrates that when weaver ants were present, the minor pest insects of mealy bugs and aphids were present, and predators and parasitoids of these pests were also present, resulting in very little damage to the cashew crop It is worthwhile mentioning that during the wet season (cashew tree dormancy or leaf flush), the mean level of flushing shoots with aphids was higher in the IPM plot than in the farmer’s plot (Table 3) This is because at this time of year, trees had very low numbers of flushing shoots which were fully patrolled by weaver ants, especially shoots with aphids Therefore, the natural enemy activity was reduced On the other hand, during the wet season, aphids cannot much damage to trees and should not affect cashew yield the following year Instead, they provide food for weaver ants, keeping the ant population stable The control strategies for thrips, branch borers and stem-root borers can fit the cashew IPM program well The key component of the cashew IPM program is weaver ants This ant is very susceptible to many kinds of toxic insecticides, such as trichlorfon, dimethoate, carbaryl, etc Therefore, when weaver ants are used in cashew orchards, no toxic insecticides can be use Although weaver ants can manage a lot of insect pests, they have limited ability to control thrips on developing apples and nuts and the larvae of branch borers and stem-root borers Hence, the methods developed for controlling these pests should not be detrimental to weaver ants To control thrips, abamectine seemed to be effective, and it was not harmful to weaver ants in the laboratory experiments In our plan, abamectine will be tested in field experiments in late 2008 before it can be recommended to cashew farmers For branch borer control, the initial damage symptoms caused by young larvae is easy to recognize on mature shoots (Fig 7) between July and August, which is the cashew tree dormant period and is also a good time for tree pruning Therefore, July is a good time to start the monitoring based on the damage symptoms and to control the pest For young trees (2-3 years old) that are initially infested by the borer, shoots with the damage symptoms (Fig 7) should be cut, and this work can be combined with general tree pruning practice The cut material should be taken out of the orchards for making compost or burying underground For production trees that are repeatedly infested by branch borers, apart from the removal of the shoots with initial damage symptoms, the branches that are heavily damaged should be removed For branches that clearly show dark brown larvae excreta at regular intervals along the branch (Fig 7), the lowest larvae excreta should be located and removed, and BT or a contact killing insecticide solution should be injected into the tunnel with a syringe, and then the hole should be plugged with a cotton swab containing the same material Such methods were used in Mr Bi’s orchard July is also a good time for the stem-root borer’s control Based on the oviposition behaviour of adults, the initial damage symptoms (Fig 8) can be easily identified on the tree trunk between the base and one meter above the ground, and young larvae can be easily found and killed with a knife (Fig 8) This is particularly effective protection for young trees from stem-root borers For orchards with old trees (> 10 years old), due to the fact that stem-root borer adults prefer to oviposit on infested trees, the heavily-infested trees or major branches should be cut down and removed out of the orchards to reduce ovipisition cue Once the wood has dried out sufficiently, it should be burned to kill all the remaining larvae and eggs Painting tree trunks up to one meter high from the ground with whitewash materials should also reduce adult oviposition It is evident that trees with severe or moderate infestation may not be saved, and so, the control at early infestation stage is critical Trees 23 repeatedly damaged for 2-3 years should be injected with BT or a contact killing insecticide solution into the tunnel with a syringe to kill the larvae after removal of the bark with excretion materials The hole should be plugged with a cotton swab soaked in a mixture of carbon disulfide, naphthalene and creosote Finally, the wound should be sealed with clay or cattle dung In summary, the control of branch borers and stem-root borers involves the monitoring, the removal of young larvae and the chemical injection This strategy should have no negative effect on weaver ants so that it can be integrated into the cashew IPM program Based on the results and general farming practice from the IPM plots, a cashew IPM program which is suitable for cashew growing conditions in Vietnam has been developed and briefly summarised in Appendix 24 Appendix The Integrated Pest Management Program for Cashew Growers in Vietnam Based on characteristics of cashew tree development in Vietnam, a year is divided into four periods: (1) dormancy or leaf flush, which is the wet season (June – September); (2) pre-flowering flush, which is the beginning of the dry season (September – mid October); (3) flowering, nut setting and fruiting, which is the dry season (November – Early February); and (4) harvest and post harvest, which is the late dry season and beginning of the wet season (February - April) For each period, Table lists a number of farming activities together with Chapter references of the Cashew Manual in brackets This is for farmers to understand when to what, and how to it An empty box is provided at the beginning of each farming activity (Table 1) Put a tick in each empty box when you complete an activity This is for mature orchards For either young or old orchards, this program can be modified accordingly Table Farming activities in each cashew phenological period for cashew growers in Vietnam Cashew phenology Dormancy or leaf flush (the wet season) Pre-flowering flush (beginning of the dry season) Flowering, nut setting and fruiting (the Month IPM activities June September □ Monitoring and managing weaver ant colonies September –mid October November – January for pest control (see 7.2.1.5 for details); □ Controlling stem and branch borers (4.9, 4.10); □ Pruning (3.5.1.1); □ Fertilizing (3.5.1.2); □ Weeding (3.5.1.3); □ Compost making or mulching (3.3.2 and 3.5.1.3); □ Intercropping (3.5.1.3); □ Transplanting young trees, if needed (3.5.1.5); and □ Propagation, if needed □ Managing weaver ants for pest control; □ Monitoring the main insect pests and diseases (Part and Part 5); □ Fertilizing and/or Micro-nutrient application; and □ Bush fire prevention (3.5.2) □ Managing weaver ants for pest control; □ Monitoring the main insect pests and diseases; 25 dry season) □ Spraying soft chemicals to control thrips, if Needed (4.7); □ Spraying fungicides to control diseases, if needed (5.2); □ Irrigation, if applicable (3.5.3); February Harvest and – April post harvest (late dry season and beginning of the wet season) □ Micro-nutrient application, if needed (3.5.1.2) □ Managing weaver ants for pest control; □ Cleaning weeds and grass at the tree base or weeks before harvest; □ Collecting nuts as frequently as possible; □ Drying and storing (3.5.4); 26 ...1 Institute Information Project Name Implementation of the IPM program using weaver ants as a major component for cashew growers in Vietnam Vietnamese Institution Institute of Agricultural Science... the transplants from the farmer’s plot, almost every tree had weaver ants Apart from weaver ants, we also found ghost ants (Tapinoma melanocephalum), small sized crematogaster ants (Crematogaster... separately compared by a non-parametric Friedman 2-way ANOVA by ranks using SYSTAT statistics software The percentage yield data and field survey data were analysed by a Kruskal-Wallis one-way ANOVA