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Title: EFFECTS OF TRANSGENIC COTTON OM MORTALITY AND DEVELOPMENT OF PINK BOLLWORM (LEPIDOPTERA: GELECHIIDAE) LARVAE

Author
item Henneberry, Thomas
item Jech, Lynn
item De La Torre, Theresa

Submitted to: Southwest Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/6/2001
Publication Date: 6/1/2001
Citation: N/A

Interpretive Summary: Cottons Bt with the gene mediating production of a protein toxic to lepidopterous insects have become an important part of cotton insect pest management programs across the cotton belt. Pink bollworm (PBW) has been the key pest in Arizona and southern California cotton since the mid-1960's and Bt cottons are grown on about 65% of the cotton acreage. To be effective larvae must consume Bt toxic cotton tissue thus a feeding time factor and potential damage is involved. We compared PBW larval mortality after different times of confinement on Bt cotton bolls with larval mortality on non-Bt cotton bolls as controls. Because it is known that the amounts of toxic protein decreases in older plants, we also compared larval mortality on different age cotton fruiting forms and determined the Bt susceptibility of different age PBW larvae. Infesting Bt bolls with PBW eggs that hatched within 24-h resulted in 92% larval mortality after 48-h and 100% mortality after 4 days or longer. Larval mortality percentages decreased when larger (older) larvae were placed on bolls compared with small larvae. Generally, development for both males and females was longer on Bt bolls compared with non-Bt cotton. Ninety-three to 100% of the progeny from moth pairs from larvae that survived on Bt bolls died when transferred to Bt bolls suggesting no measurable resistance development. There were no mortality differences for larvae feeding on Bt cotton fruiting forms of different ages ranging from one-half grown flower buds to 40-day-old immature green bolls.

Technical Abstract: Pink bollworm (PBW), Pectinophora gossypiella (Saunders), larval mortality after different times of confinement on NuCOTN 33B? (Bt) cotton bolls was compared with larval mortality on Delta and Pineland 5415 cotton bolls as controls. We also compared larval mortality on different age cotton fruiting forms and determined the Bt susceptibility of different age PBW larvae. Infesting Bt bolls with PBW eggs that hatched within 24-h resulte in 92% larval mortality after 48-h and 100% mortality after 4 days or longer. There were no differences between cultivars in numbers of larval entrances holes into bolls. Larval mortality percentages decreased when older (second- and third-instar) larvae were placed on bolls compared with first-instar larvae. Generally, days to pupation for both males and females were longer on Bt bolls compared with non-Bt cotton. Ninety-three to 100% of the progeny from moth pairs from second- and third-instar larvae ethat survived on Bt bolls died when transferred to Bt bolls. There were n significant mortality differences for larvae feeding on Bt fruiting forms of different ages ranging from one-half grown flower buds to 40-day-old immature green bolls.