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ARS Home » Southeast Area » Tifton, Georgia » Crop Protection and Management Research » Research » Publications at this Location » Publication #93121
Title: MANAGEMENT OF CORN EARWORM AND FALL ARMYWORM (LEPIDOPTERA: NOCTUIDAE) INJURY ON A SWEET CORN HYBRID EXPRESSING A CRYIA(B) GENE

Author
item Lynch, Robert
item WISEMAN, B. - RETIRED
item Sumner, Harold
item PLAISTED, D. - NOVARTIS SEEDS, INC.
item WARNICK, D. - NOVARTIS SEEDS, INC.

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: The bacterium Bacillus thuringiensis (Bt for short) produces a toxin that kills several different kinds of insect larvae, but is nontoxic to humans or higher animals. Researchers isolated the gene that is responsible for production of this toxin and transferred it to sweet corn. Two of the major pests of sweet corn are the corn earworm, which is highly susceptible to the Bt toxin, and the fall armyworm, which is moderately susceptible to the toxin. We compared sweet corn containing the Bt gene, GH-0937 Bt with normal sweet corn hybrids Bonus and Silver Queen with 0, 1, 3, or 5 applications of the insecticide lannate to control corn earworm and fall armyworm. Corn was planted on April 15, May 1, May 15, June 1, and July 15, 1997, to provide different levels of insect pressure. GH-0937 Bt was highly resistant to leaf feeding by the fall armyworm and to ear injury by the fall armyworm and corn earworm. When sweet corn was planted June 15, an average of 7.9 kernels were damaged on GH-0937 Bt with no insecticide, and was reduced to 1.7 kernels with 5 applications of lannate. Silver Queen and Bonus averaged 323 and 168 kernels damaged, respectively with no insecticide, and 172 and 50 kernels damaged with 5 applications of lannate. Thus, Bt sweet corn offers an excellent opportunity to produce sweet corn with lower insecticide usage to control insects.

Technical Abstract: Research was conducted to evaluate transgenic sweet corn containing a cryIA(b) gene from Bacillus thuringiensis (Bt) and a minimal number of insecticide applications for management of injury to ears by the corn earworm (CEW), Helicoverpa zea (Boddie), and fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith). GH-0937 (Bt +), Bonus(Bt-), and Silver Queen (Bt-) sweet corn hybrids were planted 15 April, 1 May, 15 May, 1 June, and 15 June 1997, to provide different intensities of insect pressure. During ear development, methomyl was applied in 0, 1, 3, or 5 applications beginning when 50% of the plants were silking. GH-0937 exhibited a high level of resistance to leaf feeding in the whorl stage by FAW and to ear injury by the CEW and FAW. With extreme insect pressure on plants for the June 15 planting, as evidenced by the extensive damage to Bonus and Silver Queen in the whorl stage, injury to ears of GH-0937 averaged only 7.9 cm(2) when no insecticide was applied, and was reduced to an average of only 1.7 cm(2) with 5 applications of methomyl. In this same test, Silver Queen and Bonus averaged 323 and 168 cm(2) of injury, respectively, with no insecticide applications, and 172 and 50 cm(2), respectively, with 5 applications of methomyl. Injury to ears on GH-0937 was not eliminated, but was minimal and confined to a few kernels at the ear tip. Most of the observed injury was from feeding by nitidulid beetles or to an occasional large FAW larva that migrated from a susceptible plant to an ear of GH-0937 where it fed before dying. Bt sweet corn offers an excellent opportunity to develop more environmentally compatible approaches for sweet corn production.