Monitoring of insect pests, natural enemies of sweet corn and study on control methods in Khon Kaen University

บทคัดย่อ

Current situation of insect pests in sweet corn, their natural enemies and control practices wereinvestigated in the field condition during May-July 2004 in vegetable research farm within Khon Kaen University.Total 7 methods are comprising of carbofuran 3%G, one and two releases of brown earwig (Proreus simulans), onerelease of black earwig (Euborellia annulipes), two releases of brown earwig with Trochogramma sp. and tworeleases of common brown earwig (Labidura riparia). Total 22 insect pest species and 14 species of natural enemieshave been recorded. Insect pests were noted as causing severe or moderate injury were corn borer (Ostriniafurnacalis), corn earworm (Helicoverpa armigera), and aphid (Rhopalosiphum maidis); causing light injuries werecorn looper (Phytometra chalcytes), corn thrip (Frankliniella williamsi), derbid planthopper (Phenice moesta), rosebeetle (Adoretus compressus), and leaf eating beetle (Monolepta signata). Natural enemies were spiders, earwig(P. simulans), coccinellid (Menochilus sexmaculatus, Micraspis discolor), black ant (Componotus sp.) foundcommonly while big eyed bug (Geocoris sp.), mantid, green lacewing (Chrysopa sp.), predatory bug (Eocantheconafurcellata) were less prevalent. Crop damage assessment indicated that it was no plant damage from O. furnacalisduring early three surveys at day 14, 21 and 28 after planting. Plant damage at day 49 was not statistically significantdifference. However, it was highest damage in T1 at day 56 (27.5%) and statistically significant difference at P≤0.05with T2, T5, T6, T3, T4 and T7 respectively. Ear damage was found highest (12.3%) at control (T1) and wasstatistically significant difference at P≤0.05 with T5, T6 and T7 but it was not statistical significant difference withT2, T3 and T4 respectively. However yield, marketable, unmarketable ears and return cost were not statisticallysignificant differences.