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

Sci Rep. 2021 Jan 22;11(1):2101. doi: 10.1038/s41598-021-81585-x.

Abstract

The toxicity of seven biorational insecticides [five insect growth regulators (Buprofezin, Fenoxycarb, Pyriproxyfen, Methoxyfenozide, and Tebufenozide) and two oil-extracts of neem and bitter gourd seeds] against Bemisia tabaci and their selectivity for its parasitoid, Encarsia formosa were evaluated in laboratory and field conditions for 2 years (2018-2019) in Pakistan. Toxicity results demonstrate that Pyriproxyfen, Buprofezin, and Fenoxycarb proved to be effective (80-91% mortality and 66.3-84.2% population-reduction) against B. tabaci followed by Methoxyfenozide, Tebufenozide (50-75% mortality and 47.8-52.4% population-reduction), and then oil-extracts of neem and bitter gourd (25-50% mortality and 36.5-39.8% population-reduction) in the laboratory [72 h post-application exposure interval (PAEI)] and field trails (168 h PAEI), respectively. All tested biorationals, except Methoxyfenozide [(slightly-harmful/Class-II), i.e., causing mortality of parasitoids between a range of 25-50%] and Tebufenozide [(moderately-harmful/Class-III), i.e., causing mortality of parasitoids between the ranges of 51-75%], proved harmless/Class-I biorationals at PAEI of 7-days in the field (parasitism-reduction < 25%) and 3-days in the lab (effect < 30%). In laboratory bioassays, exposure of parasitized-pseudopupae and adult-parasitoids to neem and bitter gourd oils demonstrated that these compounds proved harmless/Class-I biorationals (< 30% mortality). Alternatively, Pyriproxyfen, Buprofezin, Fenoxycarb, Methoxyfenozide, and Tebufenozide were slightly-harmful biorationals (30-79% mortality) against the respective stages of E. formosa. We conclude that most of the tested biorationals proved harmless or slightly harmful to E. formosa, except tebufenozide after PAEI of 7-days (168 h) in the field and, therefore, may be used strategically in Integrated Pest Management (IPM) of B. tabaci.

MeSH terms

  • Animals
  • Azadirachta / chemistry
  • Gossypium / genetics
  • Gossypium / parasitology*
  • Hemiptera / physiology*
  • Host-Parasite Interactions / drug effects
  • Hydrazines / toxicity
  • Insecticides / toxicity*
  • Juvenile Hormones / toxicity
  • Larva / drug effects
  • Larva / physiology
  • Momordica charantia / chemistry
  • Pest Control, Biological / methods*
  • Phenylcarbamates / toxicity
  • Plant Extracts / toxicity
  • Plants, Genetically Modified
  • Pyridines / toxicity
  • Thiadiazines / toxicity
  • Treatment Outcome
  • Wasps / physiology*

Substances

  • Hydrazines
  • Insecticides
  • Juvenile Hormones
  • Phenylcarbamates
  • Plant Extracts
  • Pyridines
  • Thiadiazines
  • buprofezin
  • pyriproxyfen
  • methoxyfenozide
  • fenoxycarb
  • tebufenozide