Management of the Diamondback Moth and Other Crucifer Insect ...

esistance in P. xylostella and can trigger populationoutbreaks. In contrast to P. xylostella, C. pavonana hasnot developed resistance to the insecticides used againstit; however, its natural enemy fauna is poorly understoodand no parasitoids which could be employed for itseffective biological control are known.Despite some pioneering work on the ecology of C.pavonana that was conducted in Lembang in the 1980s(Sastrosiswojo and Setiawati 1992), little research hassince been conducted on the ecology of C. pavonana inIndonesia. In order to develop sustainable pestmanagement programs for Brassica crops, an effectivebiological control program for P. xylostella must beintegrated with effective control measures for C.pavonana (e.g. selective insecticides, manipulation ofendemic predator complexes, trap crops and other meansof host plant manipulation). Biological control can formthe foundation for IPM strategies for the management ofP. xylostella and other crucifer pests (e.g. Furlong et al.2004a, Furlong et al. 2008a) but in order to take thisapproach, a detailed understanding of pest and naturalenemy ecology is required (Furlong and Zalucki 2007;Furlong et al. 2008b).In this study, experiments were conducted in commercialhead cabbage crops in 2008 and 2009. Natural enemyexclusion techniques were used to measure the impact ofendemic natural enemies on experimental populations ofP. xylostella and C. pavonana in order to begin tounderstand the endemic natural enemy complex availablefor incorporation into IPM programmes. The experimentswere complimented by simultaneous sampling for bothinsect pests and their natural enemies.MATERIALS AND METHODSPlants, insects and field sitesHead cabbage (Brassica oleracea cv Green Coronet) waschosen as a study crop as it is widely grown in highlandregions of West Java. Potted plants were grown fromseed in 15 cm diameter pots in a screen house and rearedto the 8-10 leaf stage before use for insect rearing or the6-8 leaf stage for using in natural enemy impact studies.Laboratory cultures of P. xylostella and C. pavonanawere established in 2008 and 2009 from larvae collectedfrom cabbage crops at the Indonesian VegetableResearch Institute (IVEGRI), Lembang, West Java (6 o49’S 107 o 38’E). Similar culturing protocols werefollowed in both species. Larvae were reared inventilated plastic containers (30 cm x 20 cm x 10 cm)and fed on fresh cabbage leaves daily. When pupaedeveloped they were collected and placed in a Petri dish(9 cm diameter) which was then transferred to the base ofa large (1 m x 0.75 m x 0.75 m) screened ovipositioncage within a screen house. Upon eclosion adult mothswere supplied with fresh honey solution (10% v/v) as afood source and young (8-10 leaf stage) potted cabbageplants on which to oviposit. Oviposition plants werechanged daily and larvae of both species were allowed todevelop to the second instar on these plants before theywere transferred to plastic rearing boxes.Field experiments were conducted in commercial headcabbage crops in Lembang. In 2008 cabbage seedlingswere transplanted to the field on 10 January. The field(≈0.14 ha) consisted of 25 raised beds (40 m long)spaced 0.75 m apart. Each bed contained two parallelrows of plants; rows within a bed and adjacent plantswithin a row were spaced 0.6 m apart. In 2009 cabbageseedlings were transplanted to the field on March 5. Thefield (≈0.19 ha) consisted of 59 slightly raised beds (27.5m long) spaced 0.5 m apart. Each bed contained 3parallel rows of cabbage plants; rows within a bed were0.35 m apart and plants in the middle row were offsetfrom the plants in the 2 outer rows by 0.175 m, plantswithin a row were spaced 0.6 m apart. In both crops,agronomic and pest management practices were underthe complete control of the farmer and detailed records ofall insecticides applied were maintained. Comprehensiverecords of the crops grown in the immediate vicinity ofthe experimental crops were not kept but in both studyyears some proximate fields contained other Brassicacrops which were more mature than the experimentalcrops and others were planted with Brassica seedlingsfollowing the establishment of the experimental crop.In both 2008 and 2009 daily maximum and minimumtemperatures and daily rainfall were recorded at theIVEGRI weather station, located ≈500 m from theexperimental sites.Assessment of natural enemy impact onP. xylostella and C. pavonanapopulationsThe impact of natural enemies on experimentalpopulations of P. xylostella and C. pavonana wasevaluated by comparing survivorship of cohorts of eachinsect on cabbage plants caged to exclude arthropodnatural enemies with survivorship of cohorts on plants towhich these natural enemies had access. Cages consistedof a cylindrical central wire frame (45 cm diameter by 45cm height) covered by a fine nylon mesh sleeve (gauge≈1 mm 2 ). Modifications to the mesh sleeve allowed theconstruction of cages which completely excluded naturalenemies (the mesh was buried under experimental plantsand completely covered the top and sides of the wireframe) and the construction of cages to which naturalenemies had access (the mesh only covered the upperparts of the wire frame but the 15 cm immediately aboveground level allowed access of predators and parasitoidsto the cage) but which created the same micro-climaticconditions as the natural enemy exclusion cages (Furlonget al. 2004b).For the P. xylostella experiments eggs were collected byplacing four mated female moths (2-3 days post eclosion)in a Petri dish (9 cm diameter) with a small Chinesecabbage leaf disc (≈4 cm diameter) for 24 h underconditions of ambient temperature and humidity. Eggslaid on the leaf disc were then counted using a hand lensThe 6th International Workshop on Management of the Diamondback Moth and Other Crucifer Insect Pests 39