Laboratory evaluation of avermectin as a selective acaricide for use withMetaseiulus occidentalis (Nesbitt) (acarina: Phytoseiidae)

Abstract

The suggestion that adding a light oil to avermectin BI would increase the toxicity of avermectin to spider mites and reduce its effect on predaceous mites was tested in laboratory trials with Tetranychus urticae Koch and Metaseiulus occidentalis (Nesbitt) on almond and bean foliage. No differences were found in the toxicity of avermectin + oil vs. avermectin alone at the doses tested for T. urticae; all (0.025, 0.5, 1, and 5 ppm) were highly toxic. Mortality of M. occidentalis females and larvae was not different on avermectin + oil vs. avermectin alone, but females produced more progeny on the avermectin + oil-treated foliage. At doses of 0.5 to 5 ppm, avermectin was sufficiently toxic to deplete predator populations in the field. Development of predator larvae on avermectin + oil and on avermectin alone was not different. Avermectin + oil on almond foliage aged outdoors was highly toxic after 96 h to T. urticae adults but M. occidentalis larvae survived well on residues by 96 h.M. occidentalis female survival and productivity were not different from the controls by 48 h. Hence a predator mite population might recover through larvae hatching onto residues. Avermectin + oil (3 ppm) residue on bean foliage held outdoors was still highly toxic to T. urticae after 33 days. In contrast, M. occidentalis females and larvae survived well on 48-to 96-hour-old residues. Neither predators nor spider mites placed on treated foliage (3 ppm) were able to reach untreated foliage in tests using bean plant seedlings with one leaf sprayed and one left unsprayed.Furthermore, when M. occidentalis females were exposed to 3 ppm avermectin for 300 s or longer, mortality was significant and the fecundity of females that had been exposed for as few as 30 s was reduced significantly. Thus, while avermectin is significantly more toxic to T. urticae than to M. occidentalis, its value as a selective acaricide will depend upon learning to use it at rates that will allow the retention of sufficient prey so that surviving predators can persist. Based on these laboratory tests, such selective doses are likely to lie below 1 ppm and can best be determined in field trials.

Toxicity of Imidacloprid-Treated Spheres to Caribbean fruit fly, Anastrepha suspensa (Diptera: Tephritidae) and Its Parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) in the Laboratory

“…After 24 h, adult parasitoids appeared paralyzed, due to the combined activity of Kinetic and abamectin. Abamectin alone had moderate or low residual toxicity to Aphytis melinus DeBach and Rhizobius lophanthae (Blaisdell), important natural enemies of diaspidiid scales (Bellows & Morse 1993), and the predatory mite Metaseiulus occidentalis (Nesbitt) (Hoy & Cave 1985). This insecticide was found to be compatible with IPM programs against the citrus mealybug, Planococcus citri Risso, due to its selectivity to larvae of Cryptolaemus montrouzieri Mulsant and adults of Leptomastix dactylopii Howard (Yumruktepe et al 1996).…”

Sublethal effects of fenpyroximate and pyridaben on two predatory mite species, Neoseiulus womersleyi and Phytoseiulus persimilis (Acari, Phytoseiidae)

“…The results suggest that fenpyroximate could be used for selective METI in a IPM program with biological control agent, N. womersleyi, because fenpyroximate did not alter the population growth rate at the field recommended concentration. However, care should be taken in translating these laboratory tests results into predictions of field performance (Hoy and Cave 1985;Zhang and Sanderson 1995). Kogan (1986) emphasized the need to base pest management decision in the field on sound principles of population ecology.…”

Biochemical Processes Related to Insecticide Action: an Overview

“…The compound is specifically toxic to phytophagous mites and to a select panel of insect species, but it is markedly less potent against some lepidopteran and homopteran species (Dybas 1989;Lasota and Dybas 1991). It is considerably less toxic to beneficial insects such as honey bees, parasitoids and predators (Hoy and Cave 1985;Dybas 1989;Zhang and Sanderson 1990) and may be considered a selective insecticide. Despite its rapid decomposition, abamectin provides residual activity in the field due to its translaminar activity (Wright et al 1985;Dybas 1989).…”