Delayed development of the whitefly （Bemisia tabaci） and increased parasitism by Encarsia bimaculata in response to sublethal doses of piperonyl butoxide

Effects of sublethal piperonyl butoxide （PB） on parasitization of Bemisia tabaci （Gennadius） （Hemiptera： Aleyrodidae） by Encarsia bimaculata Heraty et Polaszek （Hymenoptera： Aphelinidae） were evaluated both in cage and greenhouse experiments. When first, second and third instar B. tabaci nymphs were treated with PB, all but the first instar were significantly prolonged. Data indicated that sublethal PB could improve E. bimaculata parasitism rates without influencing parasitoid eclosion rates. Prolonged development increased rates of parasitism by E. bimaculata, from 17.6% to 24.7% in cages, presumably by increasing the duration of host exposure. Sublethal PB combined with E. bimaculata as an integrated approach to control B. tabaci was evaluated using life table parameters under greenhouse conditions. Indices of population trend （I） calculated from life tables were estimated at 4.6 for B. tabaci exposed to PB and parasitoids compared to 14.1 with parasitoids alone and 23.5 in un- treated controls. The results showed that after PB was sprayed and parasitoids introduced, development ofB. tabaci was delayed and the peak of each stage was postponed. The older nymphal stage had highest mortality, primarily due to mortality caused by parasitism by E. bimaculata.

Bioefcacy and durability of Olyset® Plus, a permethrin and piperonyl butoxide-treated insecticidal net in a 3-year long trial in Kenya

Background:Long-lasting insecticide nets(LLINs)are a core malaria intervention.LLINs should retain efficacy against mosquito vectors for a minimum of three years.Efficacy and durability of Olyset®Plus,a permethrin and piperonyl butoxide(PBO)treated LLIN,was evaluated versus permethrin treated Olyset®Net.In the absence of WHO guidelines of how to evaluate PBO nets,and considering the manufacturer’s product claim,Olyset®Plus was evaluated as a pyrethroid LLIN.Methods:This was a household randomized controlled trial in a malaria endemic rice cultivation zone of Kirinyaga County,Kenya between 2014 and 2017.Cone bioassays and tunnel tests were done against Anopheles gambiae Kisumu.The chemical content,fabric integrity and LLIN survivorship were monitored.Comparisons between nets were tested for signifcance using the Chi-square test.Exact binomial distribution with 95%confdence intervals(95%CI)was used for percentages.The WHO efcacy criteria used were≥95%knockdown and/or≥80%mortality rate in cone bioassays and≥80%mortality and/or≥90%blood-feeding inhibition in tunnel tests.Results:At 36 months,Olyset®Plus lost 52%permethrin and 87%PBO content;Olyset®Net lost 24%permethrin.Over 80%of Olyset®Plus and Olyset®Net passed the WHO efcacy criteria for LLINs up to 18 and 12 months,respec‑tively.At month 36,91.2%Olyset®Plus and 86.4%Olyset®Net survived,while 72%and 63%developed at least one hole.The proportionate Hole Index(pHI)values representing nets in good,serviceable and torn condition were 49.6%,27.1%and 23.2%,respectively for Olyset®Plus,and 44.9%,32.8%and 22.2%,respectively for Olyset®Net but were not signifcantly diferent.Conclusions:Olyset®Plus retained efcacy above or close to the WHO efcacy criteria for about 2 years than Olyset®Net(1–1.5 years).Both nets did not meet the 3-year WHO efcacy criteria,and showed little attrition,comparable physical durability and survivorship,with 50%of Olyset®Plus having good and serviceable condition after 3 years.Better community education on appropriate use and upkeep of LLINs is essential to ensure efectiveness of LLIN based malaria interventions.

Comparative Efficacy of Three Commercial Ectoparasiticides against Fleas in Naturally Infested Dogs

Fleas that infest pets are considered important parasites of both animals and humans. These insects cause irritation and can also transmit zoonotic diseases. Research has led to a rapid expansion in the development of flea control products. In the face of a market that offers dozens of commercial ectoparasiticides for dogs and cats, pet owners and veterinarians must be provided with evidence to support their decision to select a product to control fleas. To compare the efficacy of three commercially available products against companion animal fleas, a trial was conducted on naturally-infested dogs in order to validate their pulicidal activity. Thirty-two flea-infested dogs with fleas were divided into 4 groups (n = 8) for each treatment. Group 1 received one pipette of permethrin as a spot-on dose of 650 mg/ml. The second group received 9.7% fipronil as a spot-on formulation. Group 3 was treated with a spot-on formulation of permethrin 7.40% plus piperonyl butoxide at 7.40%. Group 4 remained as the untreated control. Fleas of all experimental dogs were examined and counted on days 0, 3, 7, 14, 21 and 28 to determine the percentage of flea reduction. Results showed a 100% efficacy for all tested products. Identified species were: Ctenocephalides felis (75.7%), Ctenocephalides canis (15.9%) and Pulex irritans (9.5%). Based on these results, it was concluded that the three anti-flea products evaluated under the conditions of this study, produced an excellent efficacy as from the third day after treatment.

Aflatoxin B1： Toxicity, bioactivation and detoxification in the polyphagous caterpillar Trichoplusia ni

Trichoplusia ni caterpillars are polyphagous foliage-feeders and rarely likely to encounter aflatoxin B1 （AFB1）, a mycotoxin produced by Aspergillus flavus and A. parasiticus, in their host plants. To determine how T. ni copes with AFB 1, we evaluated the toxicity ofAFB 1 to T. ni caterpillars at different developmental stages and found that AFB 1 tolerance significantly increases with larval development. Diet incorporation of AFB 1 at 1μg/g completely inhibited larval growth and pupation of newly hatched larvae, but 3μg/g AFB 1 did not have apparent toxic effects on larval growth and pupation of caterpillars that first consume this compound 10 days after hatching. Piperonyl butoxide, a general inhibitor of cytochrome P450 monooxygenases （P450s）, reduced the toxicity of AFB 1, suggesting that AFB1 is bioactivated in T. ni and this bioactivation is mediated by P450s. Some plant allelochemicals, including flavonoids such as fiavones, furanocoumarins such as xanthotoxin and imperatorin, and furanochromones such as visnagin, that induce P450s in other lepidopteran larvae ameliorated AFBI toxicity, suggesting that P450s are also involved in AFB 1 detoxification in T. ni.