Báo cáo Nghiên cứu khoa học Integrated pest management using weaver ants as a major component for cashew

Collaboration for Agriculture and Rural Development (CARD) Program 176 INTEGRATED PEST MANAGEMENT USING WEAVER ANTS AS A MAJOR COMPONENT FOR CASHEW Project title: Implementation of the IPM program using weaver ants as a major component for cashew growers in Vietnam Project code: CARD 029/05/VIE Author(s): Prof. Keith Christian1, Dr. Renkang Peng1, La Pham Lan2 and Nguyen Thanh Binh2 Project Implementing organisations: 1 Charles Darwin University, Australia 2 Institute of Agricultural Science of South Vietnam SUMMARY Cashew is a very important crop in Vietnam, and the government has designated cashew development as a national priority. Productivity of cashew has increased since 2002, but the extensive use of pesticides has caused health problems to farmers, their animals and the environment. The cashew IPM programs using weaver ants as a key element developed at Charles Darwin University (CDU) do not involve high toxic insecticides, but result in high yield and nut quality. This project is to use the CDU cashew IPMs to develop and implement an integrated cashew improvement (ICI) program that will work under Vietnamese conditions. An ICI manual and an ICI photo book that work in Vietnam have been developed at 500 and 3000 copies, respectively, and used in the TOT and FFS training, and the positive comments on the materials are received. The project has produced 113 competitive TOT trainers, who have successfully conducted 98 FFSs, resulting in 2,448 knowledgeable farmers. Demonstration orchards produced 13% more net profit in the ICI plot than in the farmers’ plot. Over 95% of farmers were pleased with the FFS training contents, methods and the results of demonstration orchards. The project has produced benefits for small-holders and aspects of capacity building, and improved farm environment, farm health and crop sustainability. There is a high demand of FFS training by local cashew growers. Keith Christian, Renkang Peng, La Pham Lan & Nguyen Thanh Binh 177 1. Introduction Cashew (Anacardium occidentale) is an important crop in Vietnam, and the government has designated cashew development as a national priority. The area growing cashew is about 430000 ha located in Central Highlands, South Central Coast and South East region. Cashew is planted mainly in inverse soils that are low in fertility and with low precipitation. For years, cashew plants were considered as a forestry plant so that the growers did not consider any intensive techniques such as fertilization or plant protection (David, 1999). When the decree of Prime Minister signed in 7 May 1999 on the development of cashew production was released, the growing area of this plant for exports expanded rapidly in Southern Vietnam. However, the productivity of cashew is low because of serious damage from insect pests and inadequate farm management. Insect pests of cashew plants has identified that lepidopterans and hemipterans are predominant (An, 2003; Lan et al., 2002). Generally the use of insecticides is a common practice by farmers to control insect pests. In some cases the efficacy of insecticides was not proven due to misuse and farmer use of insecticides as a preventive tool. To achieve high yields most growers rely heavily on insecticides, resulting in increased costs, pest resistance, environmental pollution and the reduction of natural enemies and pollinators. The suggestion of using a biological agent as weaver ant (Oecophylla smaragdina) instead of insecticides is not new but has potential as a control measure. In the Mekong Delta the application of weaver ants can control insect pests in citrus orchards and also give fruit with few blemishes. The use of weaver ants as a biological control agent of insect pests is common in the Mekong Delta (Barzman et al., 1999). Scientists from Charles Darwin University found that an IPM program that used weaver ants as a key element had been successfully used by cashew growers in Australia, Papua New Guinea and Mozambique (Peng and Duncan, 1999; Peng, 2000, 2001, 2002; Peng et al., 1999, 2004). Based on the successful examples on citrus orchards in the Mekong Delta (Vietnam) and on cashew orchards in Australia and Africa, this project was proposed with the aim of increasing cashew yield and improving nut quality. Specific objectives are (1) to conduct TOT training in cashew IPM for TOT trainers to conduct FFSs in their local region, (2) to develop an IPM cashew curriculum and a series of illustrative posters based on the cashew IPM programs developed in Australia that will work in Vietnamese conditions and (3) to assess the effectiveness of the FFS model in increasing farmer knowledge and reducing pesticide use in cashew production. 2. Research contents and methods 2.1. Research Contents A Start up workshop was held on 5 May 2006 at the Institute of Agricultural Science of Southern Vietnam (IAS). A total of 38 experts who are involved in Vietnam cashew production were invited, they came from plant protection departments, research institutions, universities, non-government organizations, agricultural services and rural departments, an insecticide company and media corporations. Organization of Training of Trainees (TOT) classes: Two TOT courses were organized. One TOT was held at the sub-PPD of Binh Phuoc province, and the other at the Hung Loc Agricultural Research Center belonging to IAS located in Dong Nai province. Two TOT courses have resulted in 60 trainees (30 each), who are currently IPM trainers in rice and vegetables in provincial sub-PPD. Because cashew trees are perennial, the period from flowering to harvesting is more important than other periods. The TOT courses ran from flowering to harvest. At each site, one demonstration cashew orchard was established to enable trainees to practice. Each demonstration orchard is 1.2 ha, divided into two treatments. One treatment was managed by the orchard owner with his current farming practices including insecticide sprays. The other was managed by the IPM program. The two TOTs of 1st year have been completed, the two TOT of the 2nd year are currently running. A total of 120 cashew IPM trainers will be available at the end of the project. Keith Christian, Renkang Peng, La Pham Lan & Nguyen Thanh Binh 178 Organization of Farmer Field School (FFS) classes: After finishing the course 60 TOT trainees will become cashew IPM trainers. The 60 IPM trainers will be divided to 30 groups (2 for each group), and each group will run one FFS. Each FFS will take 25 farmers. A total of 30 FFSs will be completed in the 1st year and a total of 750 cashew smallholders will be trained in cashew IPM. In the 3rd year, each group of “old trainees” (2 trainers) will run 2 FFSs, and each group of “new trainees” (2 each) will run one FFSs, A Base line survey was conducted in the target provinces of this project Binh Phuoc, Dong Nai, Binh Duong, Binh Thuan, Ba Ria Vung Tau, Dak Lak and Dak Nong provinces. 3. Research results and discussions 3.1 Baseline survey - Effectiveness of the FFS model in increasing farmer knowledge and reducing pesticide use in cashew production The effectiveness of the FFS training on farmers’ knowledge and farming skills has been assessed against baseline data. Of 197 questionnaires collected from the first year FFS farmers, over 95% of farmers were happy with the FFS training contents, with the training methods, and with the results from FFS demonstration orchards. More that 80% of the farmers were sure that weaver ants could control the main cashew insect pests and would improve cashew yield and nut quality. Over 80% of farmers knew how to use weaver ants, would use weaver ants, and would tell their friends and other farmers to use the ants. Farmers’ knowledge about insect pests, diseases and their natural enemies as well as general farming skills has been significantly improved (Peng et al., 2009). Farmers’ knowledge about the general farming activities has been significantly improved. Compared to the proportion of farmers conducting each of these farming activities before the FFS training, 35%, 49%, 28%, 31%, and 18% more farmers conducted weeding, mulching, irrigation, pruning and fertilizer application respectively after the FFS training. Compared to the proportion of farmers using insecticides before the FFS training, 24% fewer farmers used insecticides after the FFS training (Table 1 and 2). In addition to this, over 92% of the farmers showed a full understanding of the principles and tactics of conducting each of the above farming activities. Table 1. Number of people who used insecticides before and after the FFS training. Insecticide spray Before FFS After FFS Total Yes 180 133 313 No 17 64 81 Total 197 197 394 Pearson Chi-square statistics χ2 = 34.329; P < 0.001; df = 1. Table 2. Number of people who used insecticides and herbicides before and after the FFS training. Herbicide use Before FFS After FFS Total Yes 152 147 299 No 44 49 93 Total 196 196 392 Pearson Chi-square statistics χ2 = 0.352; P = 0.553; df = 1. In the baseline survey, farmers, on average, could only recognise < 1 insect pest species, and 37% of them could not recognise any insect pests. After the FFS training, on average, farmers could recognise 3.3 species. More than 85% of the farmers could recognise tea mosquito bugs, branch borers and stem- root borers, and over 20% of farmers could recognise thrips, shoot borers, branch borers, red caterpillars and mealy bugs, which are the major insect pests in cashew orchards. In our baseline survey, farmers could only recognise < 1 disease, and 37% of them could not recognise any disease. Besides, farmers, on average, could recognise 2 diseases. After the FFS, 92% of the farmers could recognise the most important disease ‘anthracnose’. In the baseline survey, a majority of farmers had no knowledge of the natural enemies of the pest species. After the FFS training, farmers could recognise an average of 2.2 species of natural enemies, and 100% of the farmers knew weaver ants very well. With regard to the reduction of insecticide use, 91% of the farmers used insecticides before the FFS training, but after the FFS training, only CARD 029/05 VIE – IPM for cashew using weaver ants 179 67% of the farmers used insecticides, resulting in a 24% reduction (Peng et al., 2009). This was because insect pest damage was greatly reduced after using weaver ants in their orchards. However, with the application of the ICI program, it would expect that the current level (67%) of farmers using insecticides will decrease further when farmers get more and more experience using weaver ants. Besides this, 92% of the farmers demonstrated a full understanding of when and how to use insecticides in their orchards (Peng et al., 2009). In contrast, in baseline survey, 80% of the farmers experienced various kinds of poison symptoms during or after the insecticide operations (Peng et al., 2006a). 3.2 TOT training in cashew IPM for TOT trainers to conduct FFSs in their local region A total of 113 TOT trainers have graduated from our two-year TOT training (56 in the first year and 57 in the second year (Peng et al., 2008e), and they are very competent in FFS training (Peng et al., 2008c). These TOT trainers have successfully conducted 98 FFSs in their local regions, resulting in 2,448 farmers having graduated with improved knowledge and farming skills in relation to the cashew ICI program (Peng et al., 2009). Opening a TOT course in Binh Phuoc TOT Field work in cashew garden 3.3 Field experiments in the demonstration orchards 3.3.1 Binh Phuoc orchard Based on the monitoring data, the common insect pests in this orchard were tea mosquito bugs (Helopeltis antonii), shoot borers (Alcidodes sp.), leaf miners (Acrocercops syngramma), aphids, the apple-nut borer (Nephopteryx sp), leaf rollers and branch borer. During the period of pre-flowering flush to nut development (November to March), the damage level of cashew flushing shoots, flowers or young nuts by tea mosquito bugs, shoot borers, leaf miners, aphids and leaf rollers was similar between the farmer’s plot and the IPM plot (P > 0.05; Table 3). 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 3). Red tea mosquito bug (Helopeltis antonii) Blue shoot borer (Alcidodes sp.) Leaf miner (Acrocercops syngramma) Leaf rollers Keith Christian, Renkang Peng, La Pham Lan & Nguyen Thanh Binh 180 Table 3. 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. 2008. Pest name Treatment Mean % shoots damaged /tree + SD Friedman two–way ANOVA Rank sum Statistic Tea mosquito bugs Farmer 6.5 + 3.8 14.0 Xr2 = 0.400; df = 1; P = 0.527IPM 6.7 + 3.2 16.0 Shoot borers Farmer 8.3 + 7.0 14.0 Xr2 = 0.400; df = 1; P = 0.527IPM 7.9 + 5.1 16.0 The leaf miner Farmer 1.8 + 1.6 15.5 Xr2 = 0.111; df = 1; P = 0.739IPM 1.8 + 1.5 14.5 Aphids Farmer 11.5 + 11.9 14.5 Xr2 = 0.111; df = 1; P = 0.739IPM 12.4 + 11.8 15.5 The fruit-nut borer* Farmer 0.11 + 0.69 57608.0 U = 29405.0; df = 1; P = 0.018IPM 0.01 + 0.15 56395.0 Leaf rollers* Farmer 0.4 + 1.2 56575.5 U = 28372.5; df = 1; P = 0.933IPM 0.7 + 3.4 57427.5 *, Mann-Whitney U test is used. 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. However, the average level of shoots with aphids was more in the IPM plot than in the farmer’s plot (Table 4). Table 4. 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. Pest name Treatment Mean % shoots damaged /tree + SD Friedman two–way ANOVA Rank sum Statistic Tea mosquito bugs Farmer 6.5 + 11.2 16.0 Xr2 = 8.000; df = 1; P = 0.005IPM 2.4 + 4.3 8.0 Shoot borers Farmer 5.0 + 2.0 16.0 Xr2 = 8.000; df = 1; P = 0.005IPM 2.4 + 0.9 8.0 The leaf miner Farmer 1.2 + 1.0 15.0 Xr2 = 4.500; df = 1; P = 0.034IPM 0.5 + 0.3 9.0 Aphids Farmer 9.0 + 5.9 8.0 Xr2 = 8.000; df = 1; P = 0.005IPM 13.3 + 9.6 16.0 3.3.2 Hung Loc Centre orchard 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 5). CARD 029/05 VIE – IPM for cashew using weaver ants 181 Brown aphids Damage on shoots Mealy bug damage on nuts Weaver ants farm mealy bugs Table 5. 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. 2008 Pest name Treatment Mean % shoots damaged /tree + SD Friedman two–way ANOVA Rank sum Statistic Tea mosquito bugs Farmer 1.25 + 2.64 6 Xr2 = 3.000; df = 1; P = 0.083IPM 2.49 + 3.40 9 The shoot borer* Farmer 0.64 + 1.79 5273.5 U = 2788.5; df = 1; P = 0.135IPM 0.26 + 1.06 5166.5 Leaf rollers Farmer 3.13 + 3.85 7 Xr2 = 0.333; df = 1; P = 0.564IPM 3.42 + 3.93 8 The leaf miner Farmer 2.75 + 3.83 7 Xr2 = 2.000; df = 1; P = 0.157IPM 2.65 + 4.49 5 Mealy bugs* Farmer 0.69 + 2.03 4780.5 U = 2295.5; df = 1; P = 0.088IPM 1.96 + 5.49 5659.5 Aphids Farmer 0.75 + 2.47 6.5 Xr2 = 1.000; df = 1; P = 0.317IPM 1.96 + 4.33 8.5 *, Mann-Whitney U test is used. The average number of nuts per tree were similar between the farmer’s plot and the IPM plot (P = 0.206; Table 6). The nuts were cleaner and shinier in the IPM plot than in the farmer’s plot. In the crop season 2008-2009, the demonstration orchard at Hung Loc Centre of the IAS has also been successfully completed. The weaver ant abundance was over 50% from November 2008 to May 2009, the ant populations were stable during the period of cashew flowering and fruiting (January – March). Regular monitoring showed that the main insect pests are tea mosquito bugs, the shoot borers, leaf rollers, leaf miners, mealy bugs and aphids. The mean damage level on cashew flushing shoots, flowers or young nuts by shoot borers, leaf rollers and leaf miners was similar between the farmer’s plot and the IPM plot. Although tea mosquito damage was higher in the IPM plot than in farmer’s plot, the damage caused by tea mosquito bugs was < 5 %, which is lower than the control threshold determined by Peng et al. (1997). The damage caused by mealy bugs and aphids was higher in the IPM plot than in the farmer’s plot, but the average damage was <1% and <2% for mealy bugs and aphids respectively (Table 7). Table 6. The number of cashew nuts per half canopy in the farmer’s plot and the IPM plot of the demonstration orchard at Hung Loc Centre, Dong Nai, Vietnam. 2008. Plot (Treatment) Number of nuts per tree (No. + SD) Rank sum 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 Keith Christian, Renkang Peng, La Pham Lan & Nguyen Thanh Binh 182 Table 7. The mean % shoots damaged by insect pests in the farmer’s plot and the IPM plot of the demonstration orchard at Hong Loc Centre, February 2008 – May 2009, Dong Nai province, Vietnam. Pest name Treatment Mean % shoots damaged /tree + SD Friedman two–way ANOVA Rank sum Statistic Tea mosquito bugs Farmer 2.89 + 5.22 19.5 Xr2 = 4.500; df = 1; P = 0.034IPM 4.28 + 5.82 25.5 The shoot borer Farmer 1.51 + 3.84 18.5 Xr2 = 1.000; df = 1; P = 0.317IPM 1.95 + 4.72 20.5 Leaf rollers Farmer 3.25 + 7.19 19.0 Xr2 = 0.333; df = 1; P = 0.564IPM 4.08 + 7.47 20.0 The leaf miner Farmer 1.31 + 3.39 22.0 Xr2 = 1.000; df = 1; P = 0.317IPM 2.10 + 4.88 23.0 Mealy bugs Farmer 0.08 + 0.92 17.5 Xr2 = 4.000; df = 1; P = 0.046IPM 0.34 + 2.37 21.5 Aphids Farmer 0.18 + 1.17 17.5 Xr2 = 13.000; df = 1; P < 0.001IPM 1.75 + 4.36 30.5 The average yield of cashew nuts per tree were similar between the IPM plot and the farmer’s plot (Table 8), but the nuts were cleaner and shinier in the IPM plot than in the farmer’s plot. Table 8. The average yield of cashew nuts per tree in the farmer’s plot and the IPM plot of the demonstration orchard at Hong Loc Centre, 2009 Dong Nai, Vietnam. Plot (Treatment) Yield (kg /tree + SD) Rank sum Farmer (use insecticides) 3.8 + 1.4 15.5 IPM (use weaver ants only) 3.7 + 1.7 14.5 Friedman two–way ANOVA Xr2 = 0.111; df = 1; P = 0.739 3.3.3 Trang Bom orchard In Dong Nai demonstration orchard, the third year experiment (crop season 2008-2009) has been successfully completed. After the ghost ant was identified as the major factor to be responsible for the failure of the main insect pest control by weaver ants in the first and the second year (Peng et al. 2008d), to avoid a strong competition between ghost ants and weaver ants, existing weaver ants colonies on the orchard boundary were used, together with the management of boundary trees. This method was successfully to keep weaver ant populations high and stable on cashew trees. The weaver ant abundance was over 60% from November 2008 to May 2009, and the ant populations were stable during the period of cashew flowering and fruiting. Regular field observations showed that, in contrary to the results of the previous two years (Peng et al., 2008d), weaver ants behaved normally, and they were active to forage on flushing shoots, flowers and developing nuts. No competition for food between weaver ants and ghost ants was observed. The average number of flushing shoots and flowers was similar between the IPM plot and the farmer’s plot. The main insect pests in this orchard are tea mosquito bugs, the shoot borer, leaf rollers, leaf miners, mealy bugs and aphids (Table 9). The mean damage level on cashew flowers or young nuts by each of these pests was similar between the farmer’s plot and the IPM plot, with the exception of aphids that the damage level was higher in the IPM plot than in the farmer’s plot. However, the average aphid damage was < 2% (Table 9). The average yield of cashew nuts per tree were higher in the IPM plot than in the farmer’s plot (Table 10). Also, the nuts were cleaner and shinier in the IPM plot than in the farmer’s plot. Keith Christian, Renkang Peng, La Pham Lan & Nguyen Thanh Binh 183 Table 9. The mean % shoots damaged by insect pests in the farmer’s plot and the IPM plot of the demonstration orchard at Mr Bi’s orchard, 10 November 2008 – 10 April 2009, Dong Nai province, Vietnam. Pest name Treatment Mean % shoots damaged /tree + SD Friedman two–way ANOVA Rank sum Statistic Tea mosquito bugs Farmer 3.70 + 6.09 18.0 Xr2 = 3.000; df = 1; P = 0.083IPM 2.42 + 3.97 15.0 The shoot borer Farmer 1.37 + 4.07 16.5 Xr2 = 1.000; df = 1; P = 0.999IPM 0.89 + 2.63 16.5 Leaf rollers Farmer 5.35 + 8.40 16.0 Xr2 = 1.000; df = 1; P = 0.317IPM 5.12 + 7.82 17.0 The leaf miner Farmer 1.75 + 4.33 16.5 Xr2 = 1.000; df = 1; P = 0.999IPM 1.46 + 3.39 16.5 Mealy bugs Farmer 0.01 + 0.15 15.5 Xr2 = 2.000; df = 1; P = 0.157IPM 0.09 + 0.55 17.5 Aphids Farmer 0.07 + 1.00 11.5 Xr2 = 10.000; df = 1; P = 0.002IPM 1.68 + 6.30 21.5 Nuts in the IPM plot Nuts in farmer’s plot Table 10. The average yield of cashew nuts per tree in the farmer’s plot and the IPM plot of the demonstration orchard at Mr Bi’s orchard, 2009 Dong Nai, Vietnam. Plot (Treatment) Yield /tree (kg) + SD Group t test Farmer (use insecticides) 13.3 + 2.2 t = -2.068; df = 75; P = 0.042IPM (use weaver ants only) 14.3 + 2.0 3.4 Development of an IPM cashew curriculum and an IPM cashew photo book The cashew curriculum has been developed based on long-term field experiments and field surveys in major cashew growing provinces (Peng et al., 2008d). It is entitled “The integrated cashew improvement (ICI) program using weaver ants as a major component - Manual for ICI program trainers and extension officers in Vietnam”. As planned, the manual includes up-to-date information about cashew botany, breeding, culture practice, diseases and their control, insect pests and their damage, natural enemies, integrated pest control, the role of weaver ants, weaver ant keeping, cashew harvest, a checklist of the ICI program at different growing periods, and four appendices of guidelines for TOT and FFS training and for monitoring pest damages and Keith Christian, Renkang Peng, La Pham Lan & Nguyen Thanh Binh 184 weaver ant abundance (Peng et al., 2008a). This book was published in 500 copies. An ICI cashew photo book has also been developed based on long-term field experiments, field surveys and laboratory rearing (Peng et al., 2008d). The ICI photo book covers cashew variety selection, advanced farming practice, major diseases, major insect pests, the main natural enemies, the integrated pest control methods, role of weaver ants, weaver ant keeping techniques, and the summary of the ICI programme (Peng et al., 2008b). This book was published in 3000 copies. 4. Conclusions and recommendations Total of 113 TOT trainers have graduated from our TOT training, and they are very competent in FFS training. These TOT trainers have successfully conducted 98 FFSs in their local regions, resulting in a total of 2,448 ICI program farmers with improved knowledge and farming skills. An ICI manual for TOT trainers and extension officers in Vietnam and an ICI photo book for cashew growers in Vietnam has been developed and used by our TOT trainers in the FFS training. These manual were published in 500 and 3000 copies, respectively. After the FFS training, the percentage of farmers who used insecticides, reduced to 24%. The current level (67%) of farmers using insecticides is expected to decrease further when farmers get more and more experience using weaver ants. 92% of the farmers demonstrated a full understanding of when and how to properly use insecticides in their orchards. Over 95% of farmers were happy with the FFS training programs, with the training methods, and with the results of demonstration orchards. There was high demand for the FFS training of the ICI program by cashew smallholders who have not been trained because of the positive impact of the FFS farmers. Reference 1. An, Tran Thi Thien. 2003. Preliminary results of study on the cashew pests in Binh Phuoc Province. Paper presented at the Workshop on Plant protection serving to the policy of cultivation structure shifting in Central Highland and Southern Region. Vung Tau, 24-25 June 2003. 2. Barzman, Marco S., Nick J. Mills, and Nguyen Thi Thu Cuc. 1999. 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