SURVEY ON MANAGEMENT OF SPOTTED POD BORER (Maruca vitrata Fabricius) ON YARDLONG BEAN IN CHITWAN, NEPAL

A household survey was conducted during January 2012 in Gunjanagar, Dibyanagar and Sukranagar Village Development Committee of Chitwan district to know the socioeconomic status, status of spotted pod borer and its management practice. The survey included purposive random sampling methods in 35 yardlong bean growers. Most of commercial farmers have been growing since 3-7 years. Nearly three fourth of the farmers considered spotted pod borer as a major pest of yarldlong bean in Chitwan. Most of them considered more than 60% loss caused by spotted pod borer if no management practice is applied. Almost all sprayed chemical pesticides for management of spotted pod borer and nearly three fourth of them used more than one chemical pesticides alternately for management of spotted pod borer.One third farmers (31.43%) applied chemical pesticides in 4-7 days interval and one third of them (31.43%) applied chemical pesticides in 7-10 days interval after beginning of flowering for management of spotted pod borer. Almost all farmers (94.29%) knew adverse effect of pesticides on human, environment, natural enemies and other animal. Majority (94.29%) of farmers harvested pods after 1-3 day of spray of chemical pesticides and very few (14.29%) of commercial grower of this area get training in insect pest management.


Introduction
Yardlong bean (Vigna unguiculata L. subsp. sesquipedalis Verdc.) is cultivated subspecies of cowpea, which is also known as Chinese long bean or asparagus bean or snake bean. The production of yardlong bean is 30,977 metric tons from an area of 2,772 ha with productivity of 11 mt/ha in Nepal (MoAD, 2012).It is being attacked by insect pests at flowering and post-flowering stage, which is a major factor to limit the production (Jackai et al., 1992). Among them, spotted pod borer (Maruca vitrata Fabricius), pod sucking bug (Clavigralla gibbosa Stal.) and thrips (Megalurothrips sjostedti Trybom) reduce the productivity significantly. The spotted pod borer, Maruca vitrata Fabricius is one of the major pest of cowpea in the tropics (Jackai and Daoust, 1986). The loss due to this pest is estimated 54.4% in yardlong bean in Bangladesh (Ohno and Alam, 1989).The pod borer larvae damage flower buds, flowers, green pods and seeds of cowpea (Singh and Jackai, 1988) thereby reducing production. The spotted pod borer is also important pest of yardlong bean grown in Chitwan. To reduce the crop loss, farmers are using of chemical pesticides indiscriminately. The indiscriminate use of synthetic pesticide increase resistance of pest species, chemical residues in treated food material (Champ and Dyte, 1976;Snelson, 1987;Georghion and Lagumes, 1991) and health hazard to users and livestock. Thus, farmer survey was carried out to know the status of spotted pod borer and trend of using chemical pesticides in major vegetable growing area of Chitwan.

Material and Methods
A household survey was conducted to know the socioeconomic condition, general information of spotted pod borer and their extent of damage including their management practices. The survey included purposive random sampling methods in 35 yardlong bean growers. Semi structured questionnaire was prepared and necessary information was collected. Sample households were used for pretest survey and necessary improvements were made in questionnaire. Total 35 yardlong bean growing farmers of three VDCs of Chitwan, namely: Gunjanagar, Dibaynagar and Sukranagar were selected. The collected information were tabulated and analyzed using Microsoft Excel and SPSS software and interpreted with the help of relevant literature.

Farmers' profile
More than half of the respondents (57.15%) were having secondary level of academic qualification. Very few respondents were Illiterate (5.71%). Nearly 23% of respondent had primary education and 14% farmer had higher education (Table 1).
Majority (60%) of yardlong bean growers had 5-8 members per household, whereas national average was 4.70 member per household (MoAD, 2012) (Table 2). Similarly, 11.43% of respondents had family size of more Research Article than 8 members and rest respondents (28.57%) had family size of 4 or less than 4 members. About 31.43% of yardlong bean grower cultivated yardlong bean commercially up to in 0.13 ha land (Table  3).Similarly, 28.57% of them cultivated in 0.13-0.23 ha, 17.14% in 0.23-0.33 ha and 22.86% of total respondents grew in more than 0.33 ha of land. About 37.14% of respondent were growing yardlong bean since 0-3years, 54.29% were growing yardlong bean since 3-7 years, years and few (5.71%) were growing yardlong bean since 7-10 years and very few (2.86%) were growing yardlong bean since 10 years before (Table 4).

Farmers' knowledge on pest, natural enemies and pollinators
Farmers considered spotted pod borer, flower thrips, leaf hopper, mite were the major pests of yardlong bean causing significant yield reduction in Chitwan. Nearly three-fourth of them (74.29%) considered spotted pod borer as major pests (Fig. 1). Sharma (1998) also reported that spotted pod borer; M.vitrata Fabricius as major pests of legumes in tropics and subtropics.

Fig. 1. Farmers' rating on the major damaging pests of yardlong bean by farmers
More than half of respondents (57.14%) reported more than 60 percent of damage caused by spotted pod borer in normal condition. Ohno and Alam (1989) also reported that M. vitrata Fabricius caused 54.4% pod damage in Bangladesh in yardlong bean. Similarly, Vishakantaiah and Jagadeesh Babu (1980) observed 9-51% pod infestation at Banglore. (Table 5) Over two-third (68.58%) of respondents considered high temperature and high rainfall responsible for pod borer infestation. About one fourth (25.71%) considered high temperature and low rainfall as suitable environment for pod borer infestation and very few (5.71%) considered normal temperature and normal rainfall responsible for pod borer infestation (Table 6).
Nearly two-third of farmers (62.86%) considered pod borer infestation begin both in pod formation and flowering stage of yardlong bean. Earlier instars are capable of damaging flowers while older instars are capable of boring into pods and consuming the developing grains (Taylor, 1967). (Table 7) 74   More than one-third of farmers (42.85%) were aware about natural enemies (Figure 2). Similarly, more than half of farmers (57.14%) knew about the role of pollinators in crop production and remaining were unknown about importance of pollinator in crop production (Fig. 3).

Pest management practices
More than half of of farmers (51.43%) consulted with agro-vet to manage different pest infestation during yardlong bean production. Nearly one-third of farmers (31.43%) managed pest with their experience. Some farmers (11.43%) consult with lead farmers for managing the pest during crop production. Few farmers (5.71%) consulted both with Agro-vet and lead farmers for managing the pest. But none of farmers consult with DADO office for insect pest management (Table 8). More than half of farmers (51.43%) applied pesticides after appearance of pest while 40% of farmers spray chemical before appearance of pests. (Table 9)  (Table 10). Noorani (Chloropyriphos + Cypermethrin) and Jadhu (Triazophos + Deltamethrin) were never used alone for management of spotted pod borer but used alternately with Kingstar (Emamectin benzoate) or Fame (Flubendiamide).

43% Known
Unknown Nearly one-third of farmers (31.43%) sprayed chemical pesticides in 4-7 days interval and about one-third (31.43%) of them sprayed chemical pesticides in 7-10 days interval. 22.89% of farmers sprayed chemical pesticides in 10-15 days interval and 14.28 % of farmers spray in 2-4 days interval (Table 12). Almost all farmers (94.29%) knew adverse effect of pesticides on human, environment, natural enemies and other animal but spraying pesticides is urgent to reduce loss due to pod borer. (Fig. 4). Similarly, Atreya (2007) reported almost all respondents were aware of negative impacts of pesticides on human health and environment in his survey in Nepal.

Fig. 4: Farmers' knowledge regarding negative impact of pesticides
Majority of farmers (54.29%) reported that chemical pesticides reduced more than 50% of loss due to spotted pod borer (Table 13). Muthomi et al. (2007) also reported that chemical pesticides significantly reduced the incidence of insect pests in legumes. Majority (94.29%) of respondents harvested pods after 1-3 day of spray of chemical pesticides while 5.71% of respondent harvested 5-7 days after spray ( Figure 5). Due to fast growing character of pod they were compelled to harvest soon after few days of spraying of chemical pesticides. Yardlong beans are quick-growing and daily harvesting is often a necessity after beginning of pod production (Rubatzky and Yamaguchi, 1997). In Kathmandu valley, about 14 percent of vegetable had pesticide beyond permissible limit i.e. Rapid Pesticides Residue Analysis Laboratory found 26 out of 187 vegetable samples contaminated with pesticides beyond permissible limit (Kathmandu post, 2014) in market. This may be due to harvesting of vegetable before its waiting period and over use of pesticide in vegetable.

Fig. 5:
Waiting period for harvest of pods after spraying pesticides Out of total farmers, 85.71% of farmer did not get any training and remaining few farmers (14.29%) got training regarding crop management (Fig. 6). Out of total farmers, 74.29% of collected and burned pesticide containers, 11.43% collected and buried, 8.57% threw containers in canal and water bodies and 5.71% sold to kawadi (Table 14).

Conclusions
Farmers considered spotted pod borer (Maruca vitrata Fabricius) as major pest of yardlong bean causing more than 60 % losses in Chitwan and they used chemical pesticide as sole method of spotted pod borermanagement. The chemical pesticides were alternately used in very few interval of time in yardlong bean and harvest pod without considering waiting period. The pods are very fast growing and if they are not harvest in time market value will be reduced. But using chemical pesticides repeatedly and alternately caused very high residue in pod and plant and environment thus causing harm to human, natural enemies, environment and other animal. Only very few farmers got training in integrated pest management so government should focused on integrated pest management and also creating the awareness among the consumer.