Degree-day model for timing insecticide applications to controlDioryctria amatella(Lepidoptera: Pyralidae) in loblolly pine seed orchards

Abstract

Because Dioryctria amatella (Hulst) is a key pest in loblolly pine, Pinus taeda L. (Pinaceae), seed orchards in the southeastern United States, improved timing of insecticide applications would be valuable for its control. To time two fenvalerate (Pydrin® 2.4 EC) applications we tested four variations of a degree-day model that was developed to predicted when various proportions of D. amatella eggs would hatch during the spring generation. We compared reductions in Dioryctria spp. cone damage to unsprayed checks and a standard operational spray regime of four monthly applications of fenvalerate. In addition, we examined seeds from healthy cones to determine if sprays to control D. amatella also reduced seed damage caused by Leptoglossus corculus Say (Heteroptera: Coreidae) and Tetyra bipunctata (Herrich-Schäffer) (Heteroptera: Scutelleridae). Trials were conducted from 1984 to 1986 in two orchards in South Carolina and one in Alabama. Degree-day accumulations (threshold = 11 °C) were begun on the day when the cumulative number of male D. amatella equaled or exceeded five captured in 15 Pherocon 1C® traps baited with 100 μg of Z-11-hexadecenyl acetate. One application per year was insufficient to control D. amatella or reduced seed-bug damage. Two sprays based on D. amatella phenology significantly reduced coneworm and seed bug damage, and were as effective as four sprays applied monthly. None of the treatments reduce spring cone losses, which are primarily caused by Dioryctria merkeli Mutuura and Monroe. Several variations of the model performed well, but we suggest that the best, based on efficacy and ease of use, was when sprays were applied immediately after five males were caught (degree-day = 0) and again when the model predicted 50% of the spring generation eggs had hatched.

(3<I>Z</I>,6<I>Z</I>,9<I>Z</I>,12<I>Z</I>,15<I>Z</I>)-Pentacosapentaene and (<I>Z</I>)-11-Hexadecenyl Acetate: Sex Attractant Blend for <I>Dioryctria amatella</I> (Lepidoptera: Pyralidae)

“…The increase in attraction of D. amatella to baited traps by pentaene may provide seed orchard managers with precise and possibly earlier detection of moths in spray-timing programs, thereby adding greater ßexibility in the planning of spray applications. Therefore, the spraytiming model developed by Hanula et al (2002) for D. amatella should be revised for operational use in southern pine seed orchards to account for the increased effectiveness of the binary blend.…”

“…To date, a pheromone-based spray-timing model has been developed for only one coneworm species, D. amatella in North America (Hanula et al 2002). The only work on pheromone-based control of southern coneworms was conducted by DeBarr et al (2000).…”

“…Traps baited with (Z)-11-hexadecenyl acetate (Z11Ð16:Ac) are attractive to D. amatella, whereas the remaining three species are attracted to traps baited with (Z)-9-tetradecenyl acetate (Z9 Ð14:Ac). A degree-day spray-timing model using traps baited with Z11Ð16:Ac was developed for D. amatella (Hanula et al 2002). These authors reported that two spray applications, timed using the model, were as effective as four sprays applied monthly.…”

“…Pheromone-based monitoring can minimize the need for insecticide applications when population levels of coneworms are low as well as improve efÞciency by targeting sprays at optimal times for species that are present in the orchard at critical levels (Hanula et al 2002). Pheromone lures are known for all four species of southern coneworms (Hanula et al 1984).…”

Predicting the occurrence of alate aphids in Brassicaceae

“…Degree-day models have been used to predict the occurrence of insects, such as aphids (Hanula et al, 2002;Chakravarty & Gautam, 2004;Gomez et al, 2009), helping to improve the decisions associated with pest control in integrated pest management programs (Day & Knight, 1995).…”