Toxic and sublethal effects of buprofezin on the whitefly parasitoid Encarsia formosa Gahan

Abstract

Acute toxicity of a buprofezin-based product (commercial product Elisa 440 SC) to pupae of the whitefly parasitoid Encarsia formosa Gahan (Hymenoptera: Aphelinidae), and its effects on life history traits and population growth in F1 generation of a commercial strain (?Dutch? strain, D) and two local populations from Serbia (Bujanovac, B; Negotin, N) were examined in laboratory bioassays. All trials were carried out at 27?1?C temperature and 60?10% relative humidity, and under 16/8 h daylight/darkness photoperiod in four replications. In an acute toxicity bioassay, tobacco leaves carrying parasitoid pupae (20 pupae per replicate) were treated with a series of buprofezin concentrations covering a 10-90% mortality range, and mortality was calculated based on the number of emerging adults 9 days after treatment. The following LC50 (mg/l) estimates were obtained: 244.2, 281.5 and 199.5 (for B, N and D, respectively). The product based on buprofezin, applied to parasitoid pupae at concentrations within the LC50s and 95% confidence limits (264 mg/l for B and N; 220 mg/l for D), significantly prolonged the duration of juvenile development (2, 1.7 and 2.2 days for B, N and D, respectively, compared to control data). Females from all tested populations that emerged from the treated pupae and were exposed to the residual action of buprofezin lived shorter than control females (B, N and D by 1.5, 0.7 and 1.7 days, respectively). Also, females that emerged from the treated pupae achieved a significantly reduced level of parasitism (B, N and D by 11.7, 17.7 and 17.6 %, respectively), total adult emergence (B, N and D by 11.6, 17.8 and 17.8 %, respectively) and instantaneous rate of increase (B, N and D by 8.2, 6.8 and 12.5 %, respectively), compared to control. More precise determination of risks involved in the use of buprofezin requires its more detailed field testing. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR31043]

Efficacy of biorational insecticides against Bemisia tabaci (Genn.) and their selectivity for its parasitoid Encarsia formosa Gahan on Bt cotton

“…Some studies demonstrate that different development stages of Hymenopterous parasitoids respond differently when exposed to IGRs’ treatments 47 . There is a variable response to different stages of parasitoids to insecticides and IGRs.…”

“…There is a variable response to different stages of parasitoids to insecticides and IGRs. The effects of these compounds on predators/parasitoids are contradictory and inconsistent 46 , 47 . The results of the present study show that at the maximum PAEI (168 h), pyriproxyfen, buprofezin, fenoxycarb, and methoxyfenozide were in Class-II biorationals (slightly harmful, 25–50% mortality), neem and bitter gourd oils were Class-I biorationals (harmless, < 25% mortality), and tebufenozide was in Class-III biorationals (moderately harmful, 50–75% mortality) when emergence and mortality of E. formosa were recorded inside the treated host pseudopupae in lab bioassay.…”

“…These variations in results may exist due to difference in the concentration/dose-rates of methoxyfenozide (200 mL/0.4 ha), materials and methods used in the field (foliar spraying by 3.5-gallon knapsack sprayer with a Teejet hollow cone spray cores D3 disk using 1380-L of water/ha) and lab (foliar application by an atomizer on potted cotton maintained at 25 ± 2 °C and 75 ± 5% RH) studies, choice of test parasitoid (E. formosa), and the life stage (adult of E. formosa and unparasitized pseudopupae and larval instars of B. tabaci) used in our experiments. Some studies demonstrate that different development stages of Hymenopterous parasitoids respond differently when exposed to IGRs' treatments 47 . There is a variable response to different stages of parasitoids to insecticides and IGRs.…”

“…However, pyriproxyfen, fenoxycarb, and buprofez caused a significant decrease in the rates of parasitoids’ adult emergence 46 . Encarsia formosa females emerging from the buprofezin-treated pupae exhibited shorter lifespan (0.7–1.7 days), lower parasitism rate (11.7%), and less adult emergence (11.6–17.8%) than control treatment 47 . The results of lab bioassay of pyriproxyfen against three species of endoparasitoids [ Enearsia pergancliella, E. transvena (Timberlake) and E. formosa Gahan] and their host ( Bemisia argentifolii Bellows & Perring) show that pyriproxyfen was effective against B. argentifolii, harmless to E. pergandiella, moderately harmless to E. transvella, and moderately harmful (toxic) to E. formusa, especially pupae 48 .…”

“…However, before devising IGRs and parasitoid-based IPM strategy for B. tabaci , it is essential to investigate the non-target effects of IGRs on various biological parameters of E. formosa 46 . Some studies have shown that different development stages of Hymenopterous parasitoids respond differently when exposed to IGR treatments 41 , 42 , 46 , 47 . For example, the results of a leaf and glass-vial residue bioassays confirmed that pyriproxyfen, fenoxycarb, and buprofezin caused no considerable effects on the survival of adults of E. formosa .…”