Brassica IPM adoption: progress and constraints in south-east Asia

The Integrated Pest Management (IPM) programme for brassicas in many countries of south-east Asia follows a generic model whose basic components are: (i) Regular scouting of pests, namely the diamondback moth (DBM) and its major natural enemies to ascertain their population levels to justify insecticidal treatments; (ii) Use of pre-determined economic threshold levels (ETLs) and (iii) Incorporation of other non-chemical control measures, such as the release and conservation of parasitoids, use of trap crop and yellow sticky traps. The current empirical level of adoption by growers of this programme ranges between 50 to 100% and reasons given by growers for adopting IPM include: (i) Financial gains (higher net returns, decreased costs of control), (ii) Reduction in damage by pests, (iii) No unwarranted problems due to pesticide residues and (iv) Reduction of risks in terms of yield. However, despite the widely acknowledged benefits of the programme, the grower adoption rate in many countries has been rather slow. The major constraints to adoption were (i) the difficulty to comply with procedures determining economic threshold levels (ETLs), (ii) lack of management consideration for the other pests complex besides DBM and (iii) the weak support provided by extension agencies. The strategies to increase adoption have been outlined and these include overcoming the various current technical and non technical constraints, such as simplifying the ETLs, strengthening the linkage between research and extension and formulating technological baskets rather than technological packages. The need to crystallise inputs from social and behavioural scientists at the formulation stage of the programme was underscored. Introduction The Brassica crop system and components of the IPM programme In south-east Asia, a wide range of Brassica vegetables is cultivated practically throughout the year both in the highlands and specialised areas in the lowlands (Talekar & Shelton 1993). Although these vegetables are traditionally grown in the open, recently, in many countries, cultivation has shifted to rain or insect protected structures. Irrespective of the system, growers use intensive cultivation practices to produce the vegetables in areas averaging less than two acres. The Brassica Integrated Pest Management (IPM) programme is amongst the most well-worked IPM programmes for a particular pest problem (in this case, the diamondback moth and associated pests) in the world. In south-east Asian countries, the diamondback moth, Plutella xylostella (L.) is a pest of common concern and, considering the magnitude of its resistance problem against a wide range of synthetic pesticides, it was only natural that some of the earliest efforts in IPM were initiated in countries namely Malaysia (Loke et al. 1997, Sivapragasam et al. 1985), Indonesia (Sudarwohadi 1996), Thailand (Piyarat et al. 1997), Vietnam (Lim 1992) and the Philippines (Eusebio & Rejesus 1997). Some of the leading countries in south-east Asia and the key components of their Brassica IPM programmes are shown in Table 1. Table 1. Key components of the Brassica IPM programme in major Brassica growing countries of south-east Asia Country Key Components Malaysia Economic thresholds, incorporation of parasitoids, cultural practices, use of biopesticide, Bacillus thuringiensis (Bt) Philippines Economic thresholds, incorporation of parasitoids, IPM selective insecticides Thailand Economic thresholds, incorporation of parasitoids, use of microbial insecticides, yellow sticky traps Indonesia Economic thresholds, incorporation of parasitoids, use of microbial pesticides Vietnam Economic thresholds, Bt and other microbials, intercropping, crop rotation (cucurbits and crucifers) and cultural practices The management of diamondback moth and other crucifer pests Proceedings of the 4th International Workshop, Nov. 2001, Melbourne, Australia 12 Essentially, the IPM programme in many of these countries follows a generic model and relies on the basic components such as: (i) regular scouting of pests, namely the diamondback moth (DBM) and its major natural enemies, to ascertain their population levels to justify insecticidal treatments; (ii) use of predetermined economic threshold levels (ETLs) and, in some cases, (iii) the incorporation of other nonchemical control measures, such as the release and conservation of parasitoids, use of trap crops and yellow sticky traps. Besides these key components, other control components have been gradually added to the IPM ‘basket’ or repertoire, depending on the local pest requirements and geographical location, i.e. whether it is highlands or lowlands. Status of Brassica IPM adoption Although studies on adoption of agricultural innovations are many (see Rogers 1968), there are only a few studies done investigating the adoption of IPM innovations by farmers (Grieshop et al. 1988). However, despite the abundance of information on Brassica IPM, studies investigating the adoption process of the Brassica IPM programme by growers in the countries of south-east Asia are significantly lacking. Thus, to gauge the number of farmers adopting the IPM approach, a cursory survey was done by way of providing the relevant questions via a questionnaire to key IPM personnel in the countries of the region. Responses obtained from the four major countries are shown in Table 2. Table 2. Initial and current adoption values of Brassica IPM in four south-east Asian countries Country Initial Current Malaysia Low (30–49%) Moderate (50–79%) Indonesia High (80–100%) Moderate (50–79%) Thailand Moderate (50–79%) High (80–100%) Philippines Moderate (50–70%) High (80–100%) Depending on the country, the current empirical level of adoption by growers, as perceived by the implementers from each country surveyed, ranged between 50 to 100%. Detailed studies, however, need to be initiated to quantify whether the values given actually reflect the situation on the ground, especially for countries such as Thailand and Philippines which indicated high adoption values. These values do not categorise the farmers on the level of adoption based on the number of components farmers use in their programme. Based on the United States Department of Agriculture (USDA) standards, in IPM-based fields, adoption was categorised into three levels namely, (1) low adoption where scouting (S) and pesticide applications based on thresholds (T) for one type of pest are advocated; (2) medium IPM adoption which involved S + T plus 1 or 2 additional IPM practices being implemented and (3) high IPM adoption when S + T plus 3 or more additional IPM practices are used within the farm (Benbrook et al. 1996). Based on these criteria, the level of adoption of Brassica IPM tended to be moderate with most of the countries using at least 1 or 2 other additional components besides S and T (Table 1). With the exception of Malaysia (vide infra), no specific data are available in the literature to ascertain any trend in the adoption rate (e.g. S-curve, Rogers 1968) since the beginning of the IPM programme. Based on the survey, the reasons given by growers for adopting the IPM programme (% of respondents) include: (i) financial gains such as higher net returns and decreased costs of control (20%), (ii) reduction in damage by pests (27%), (iii) personal interest (13.5%), (iv) easy to use (6%), (v) little risk involved in terms of yield etc. (27%) and (vi) other reasons such as no residue of pesticides (6%). It is interesting to note that the latter reason did not feature prominently with the growers as, to most researchers and government policy makers, the problem of residues is an important driving force for initiating the IPM programme. Constraints to adoption Some of the reasons from respondents for the lack of interest shown by farmers in adopting the IPM programme included: (i) lack of confidence in the technology, (ii) difficulty in complying with the procedure of monitoring and counting insects based on the pre-determined economic threshold levels (ETLs), (iii) time consuming procedure and (iv) lack of understanding of the benefits of the programme. The management of diamondback moth and other crucifer pests Proceedings of the 4th International Workshop, Nov. 2001, Melbourne, Australia 13 Difficulty in complying with scouting for pests and their natural enemies Likewise in many other IPM programmes, sampling populations and treating them according to the predetermined ETLs is basic to the implementation of the Brassica IPM programme. However, counting of insects and determining the ETLs were noted to be significant problems faced by growers. Essentially, the system of monitoring insects should not be too laborious in nature since regular scouting requires labour and trained personnel–resources that are in short supply in many developing countries. In fact, the Brassica IPM programme in many countries has moved towards one of increasing complexity towards the determination of ETLs. This is exemplified by the programme in Malaysia whereby the system has evolved from one of basic threshold determination based on pest counts only (e.g. DBM larvae) (Sivapragasam et al. 1985), to that which included the counts of parasitoids (Loke et al. 1992) and eventually to one that incorporated the other key pests besides DBM (Jusoh 1997). Although these features evolved out of the inevitable necessity to portray as realistically as possible the vagaries of the Brassica system, unfortunately this process of ETL determination poses a crucial impediment to the wide adoption of the Brassica IPM programme in that country. Compounding this, Talekar and Shelton (1993) suggested that in many countries, the adoption of Brassica IPM is also hindered because many farmers cannot differentiate pests and beneficial organisms. Although alternatives to physical counting had been looked into, such as the yellow trap and pheromone trap, these tended to have limited predictive utility. Dearth of consideration to counter a complex of pests Another constraint inherent in most of the programmes is that these programmes are skewed towards the specific management of the diamondback moth (DBM) and lack the necessary control technological inputs to manage the other pests and pathogens. Therefore, a holistic approach to tackle the other occasional and recurrent pests will be crucial if the ultimate objective of maximising yields is to be achieved. For example, in Malaysia, Brassica, especially head cabbage cultivation, is limited in the lowlands by the presence of the cabbage webworm, Hellula undalis, flea beetle, Phyllotreta spp. and recently, Spodoptera exigua. A similar situation exists in the other Southeast Asian countries such as Thailand and the Philippines where H. undalis is a major problem. In addition, pathogens, Erwinia craccivora causing bacterial soft rot and Xanthomonas spp. causing bacterial wilt are major problems to Brassica cultivation both in the lowlands and highlands in many of these countries. Weak and non-sustainable extension link and transfer of technology One of the major constraints faced by IPM implementers is the difficulty to sustain the interest of those already ‘converted’ to the programme. The situation is compounded by pesticide sales pressure, lack of sustained support from the relevant change agents and dearth of external funds. More recently, probably as a result of increasing costs for legal pesticides, there are rampant sales of cheap illegal pesticides in the market. One effective mechanism to counter many of these problems will be to strengthen the existing extension component of the IPM programme. Wearing (1988) stated that “problems with the transfer of IPM technology are today identified as a principal bottleneck limiting progress with IPM worldwide despite rising pesticide costs and resistance problems.” He also stated that the lack of extensive educational programmes is a major barrier to IPM adoption. It has been underscored that promoting area-wide adoption involves key elements of training, extension and transfer of technology (Saharan et al. 1996). The pertinence of a strong extension component in the adoption process is exemplified by the situation in the Cameron Highlands, Malaysia. Figure 1 shows the rate of adoption by growers of the Brassica IPM programme initiated on an area-wide basis with strong extension support. The general trend of the adoption curve, up until 1994, revealed the typical S-shape (Rogers 1968), but after that time decreased and has remained somewhat at that level ever since. One of the key contributing factors to the downward trend is, by and large, related to the significant absence of the extension component which resulted from the termination of the IPM project in that area with the desirable management of the pesticide residue problem. Currently, it is common to see growers applying pesticides on a routine basis and the IPM adoption level stands at around 30% from a peak of almost 70% with the significant presence of the extension component. It seems obvious that the strengthening of the extension component within the adoption process could alleviate some of the major constraints faced by farmers such as their lack of confidence in the programme and its perceived benefits. The management of diamondback moth and other crucifer pests Proceedings of the 4th International Workshop, Nov. 2001, Melbourne, Australia 14 0 10 20 30 40 50 60 70 8