|Lopez, Juan DE Dios|
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: January 8, 2000
Publication Date: N/A
Interpretive Summary: Bollworm continues to be an important cotton pest because of its low susceptibility and increasing resistance to commonly-used insecticides and genetically-modified plants. We are developing a delivery system for insecticides that will kill bollworm moths directly or will prevent them from reproducing when they feed on the materials. Theoretically, these materials will consist of an attractant to attract moths into specific areas treated, a feeding stimulant to induce feeding, and an insecticide to cause control when fed upon. We evaluated moth feeding on various concentrations of insecticide (hexaflumuron) mixed with a feeding stimulant (sugar) to determine the level of feeding, lethal concentrations, and the effect of sub-lethal concentrations on reproduction. Our results showed that hexaflumuron killed the adults, but concentrations that killed the adults also reduced feeding. At concentrations that did not kill the adults and did not greatly reduce feeding, hexaflumuron had a drastic effect on hatch of the worms from eggs laid by treated females. Based on these results, hexaflumuron has potential for use in an adult bollworm control system with feeding attractants and stimulants. However, because hexaflumuron is currently not registered for field use in the US, a careful analysis of its potential is necessary before any additional studies are undertaken.
Technical Abstract: A commercial formulation of the insecticide hexaflumuron (Consult 100 EC, Dow AgroSciences) not registered for use in the U.S. was evaluated for its potential as a toxicant and reproduction inhibitor for control of adult bollworm, Helicoverpa zea (Boddie), with feeding attractants and stimulants. When mixed with 2.5 M sucrose and ingested by sex pheromone trap-captured males, hexaflumuron had significantly different 24- and 48- hour lethal concentration (LC50's) of 262.94 and 104.68 ppm (ai wt:vol), respectively. Compared with other insecticides previously evaluated, hexaflumuron has low oral toxicity and is slow-acting. Feeding response evaluations at lethal and sublethal concentrations ranging from 1 to 10000 ppm with sex pheromone trap-captured males and laboratory-reared males and females indicated that gustatory responses were significantly reduced at concentrations above 10 ppm compared with sugar solutions without insecticide. Percent larval hatch of eggs oviposited by laboratory-reared females during 3 consecutive days was drastically reduced at concentrations of 10 ppm and below when compared to eggs oviposited by females fed only sugar. Mean numbers of spermatophores per treated female were not consistently reduced compared to untreated females indicating that mating did not significantly contribute to reduction in larval hatch of eggs. When treated laboratory-reared males were paired with untreated females, there was no significant effect on frequency of mating or larval hatch of eggs; therefore, the effect of hexaflumuron on larval hatch of eggs is only on females. Based on these results, the formulation of hexaflumuron tested has potential for use as a reproduction inhibitor for adult control of bollworm with feeding attractants and stimulants.