Muhammad Ahsan Khan

Resistance development in Bemisia tabaci (Homoptera: Aleyrodidae) against a score of synthetic chemicals necessitates the exploration of novel eco-friendly integrated pest management approaches to protect field crops. In the current study, the pathogenic potential of two EPFs i.e. Beauveria bassiana and Isaria fumosorosea and two plant extracts viz. Neem leaves extract and Aloe vera leaves extract was assessed against eggs, nymphs, and adults of B. tabaci on cotton plants. Five different concentrations of EPFs (1×104, 1×105, 1×106, 1×107 and 1×108 conidia/mL) and plant extracts (10 %, 20 %, 40 %, 60 %, and 80 %) were assessed against eggs, nymphs and adults of B. tabaci. The results revealed that eggs, nymphs and adults of B. tabaci were significantly affected in terms of mortality by the tested biopesticides. Furthermore, mortality response of immatures and adults of B. tabaci was more pronounced at higher treatment concentrations and post-inoculation time intervals. Among EPFs, B. bassina was more pathogenic towards B. tabaci in comparison to its counterpart, I. fumosorosea. Similarly, Neem extracts exhibited higher mortalities as compared to Aloe vera extract. Taken together, EPFs and botanicals can provide eco-friendly and sustainable solution to manage B. tabaci. However, future studies need to conducted to find their recommended doses in field conditions.

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] againstBemisia tabaciand their selectivity for its parasitoid,Encarsia formosawere 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) againstB. tabacifollowed 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 ofE. formosa. We conclude that most of the tested biorationals proved harmless or slightly harmful toE. formosa, except tebufenozide after PAEI of 7-days (168 h) in the field and, therefore, may be used strategically in Integrated Pest Management (IPM) ofB. tabaci.