Luis E. Gomez

Bisacylhydrazine Insecticides for Selective Pest Control

In this chapter, we review five members of a novel class of chemistry, the non-steroidal bisacylhydrazine (BAH) compounds that are true agonists of the steroidal insect moulting hormone, 20-hydroxyecdysone. Also referred to as ecdysone agonists (EAs), the five BAH compounds have been commercialized for the control of lepidopteran and coleopteran larvae. Of these, four compounds (methoxyfenozide, tebufenozide, chromafenozide, and fufenozide) are predominantly toxic to lepidopteran larvae, while the fifth compound, halofenozide, is active on both lepidopteran and coleopteran larval pests in turf. The evidence for the basis of this insect selective toxicity is reviewed. The non-steroidal EA BAH insecticidal compounds are important tools in integrated pest management and insect resistance management programmes because of their selective insect toxicity, novel mode of action, and reduced risk for eco- and mammalian toxicology. In reviewing these BAH insecticides, there is greater emphasis on methoxyfenozide, the most widely used insecticide in this class of chemistry.

Response of Melon Fly (Diptera: Tephritidae) to Weathered SPLAT-Spinosad-Cue-Lure

ABSTRACT Studies were conducted in Hawaii to measure attraction of male melon fly, Bactrocera cucurbitae (Coquillett) (Diptera: Tephritidae), to SPLAT-Cue-Lure (C-L) and SPLAT-Melo-Lure (M-L) (raspberry ketone formate). Direct field comparisons of SPLAT-C-L and SPLAT-M-L at low (5%) and high (20%) concentrations indicated few differences in attraction over a 15-wk period. Subsequently, only SPLAT-Spinosad-C-L (5%) was compared with Min-U-Gel C-L with naled (standard used in California) in weathering studies. Treatments were weathered for 1, 2, 4, and 8 wk in Riverside, CA, and shipped to Hawaii for attraction/toxicity tests under field and semifield conditions by using released males of controlled ages, and for feeding tests in the laboratory. In terms of attraction, SPLAT-Spinosad-C-L compared favorably to, or outperformed the current standard of Min-U-Gel-C-L with naled. In terms of toxicity, the cumulative 24-h mortality did not differ between the two insecticide-containing C-L treatments in field cage studies after 8 wk. However, in feeding studies in which individual males were exposed for 5 min to the different C-L treatments after 4 wk of weathering, SPLAT-Spinosad-C-L demonstrated reduced mortality compared with the Min-U-GelC-L with naled, suggesting reduced persistence of the spinosad material. Spinosad has low contact toxicity and when mixed with SPLAT and C-L offers a reduced risk alternative for control of B. cucurbitae and related C-L—responding species, without many of the negative effects to humans and nontargets of broad-spectrum contact poisons such as naled.

Residual Control and Lethal Concentrations of GF-120 (spinosad) for Anastrepha spp. (Diptera: Tephritidae)

ABSTRACT The objective of this study was to determine the relationship between residual time of GF-120 (spinosad) treatment and mortality in three species of Anastrepha Schiner. Concentrations of 96, 72, 48, and 24 ppm were aged on mango leaves under field conditions for 0, 3, 7, 10, 14, 17, and 21 d after application. We found that Anastrepha ludens, A. obliqua, and A. serpentina were highly sensitive to spinosad. The effects of spinosad were not reduced over the 4 d after the initial application, even at a concentration of 24 ppm. Mortality at 14 d after the application of 72 and 96 ppm of spinosad was similar in each of the three fruit fly species. In addition, we found that 24 ppm of spinosad was consumed the most by each species even though no direct relationship between the rate of consumption per female and the dose of the product was observed, in this test, higher consumption of active ingredient was observed at a concentration of 72 ppm, for A. ludens, 48 ppm for A. obliqua, and 96 ppm for A. serpentina. Our results suggest that a spinosad concentration of 72 ppm may effectively control these pests for at least 10 d under field conditions.

Response of Female Ceratitis capitata (Diptera: Tephritidae) to a Spinosad Bait and Polymer Matrix Mixture with Extended Residual Effect in Hawaii

ABSTRACT The effectiveness of foliar applications of protein baits against pestiferous fruit flies (Tephritidae) can be adversely affected by a rapid loss of attractive volatile compounds and by rainfall due to the high water solubility of the baits. In a large coffee, Coffea arabica L., plantation in Hawaii with high and low populations of Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae), the relative attractiveness of GF-120 NF Naturalyte Fruit Fly Bait as either a 40% (vol:vol) spray solution (= GF-120 NF) or as a formulated proprietary amorphous polymer matrix (=GF-120 APM) was compared. The GF-120 APM formulations contained either, 25, 50, or 75% of GF-120 NF (wt:wt). All baits were tested in association with visually attractive yellow bait stations as a way of standardizing the evaluations. With both high and low C. capitata populations, significantly more females were attracted to the fresh sprayed GF-120 NF than to any of the three fresh GF-120 APM formulations. The attractiveness of GF-120 sprayed decreased significantly after 1 wk, whereas 1-wk-old GF-120 APM formulations were as attractive as similar fresh formulations. GF-120 APM 75% aged for 3 wk outperformed similarly-aged sprayed GF-120 NF with comparatively high C. capitata populations. With low populations, both GF-120 APM 75% and GF-120 APM 50% aged for 2 wk outperformed the similarly aged sprayed GF-120 NF. Combined findings indicate that APM mixed with either 50 or 75% GF-120 applied to bait stations can be attractive to female C. capitata for up to 3 wk longer than the standard sprayed GF-120 NF.

CHAPTER 6:The Bisacylhydrazine Insecticides

The bisacylhydrazine (BAH) insecticides are a class of green chemistry compounds very specific to the target insect pests that induce a premature molting process in the affected insects. The BAH insecticides bind to the ecdysone receptors in the target pests with a greater affinity than that observed for the natural hormone, 20-hydroxyecdysone. This confers a greater level of selectivity towards most non-target organisms present in the ecosystems where the BAH insecticides are used. The BAH insecticides act directly on immature stages of the target insects (eggs and larvae) and cause some sublethal effects, such as delayed developmental rates and reduced fecundity and fertility on the adult stage of the pests. These insecticides have very good ecotoxicological profile, having virtually no impact on most non target organisms including beneficial insects and pollinators, (bees, predators and parasitoids), birds, fish and terrestrial invertebrates. The BAH insecticides also have low-toxicity to mammals making them reduced risk materials for humans handling the products. The most widely registered BAH is methoxyfenozide, which has registrations in more than 50 countries in a variety of crops ranging from vegetables to specialty uses such as forestry and tea. Due to their characteristics, the BAH insecticides can be incorporated in insecticide resistance and integrated pest management programs. Data related to these aspects of BAH insecticides are presented.