Host Plant Mediated Susceptibility of Phenacoccus solenopsis (Tinsley) to Lecanicillium lecanii (Zimmermann) Zare and Gams, Neem Oil and their Combination

Abstract

Effects of Lecanicillium lecanii alone and in 1:1 combination with neem oil were evaluated against Phenacoccus solenopsis infesting major vegetables (eggplant, tomato, chilli, okra, pointed gourd and cucumber) and compared with cotton and whitetop weed (Parthenium hysterophorus Linn.). Marked differences were observed in the mortality of P. solenopsis amongst the vegetables and highest percent mortality (66.2 and 90.2 % at 3 and 5 DAT, respectively) was recorded in okra whereas lowest was in Parthenium (13.9 and 29.9 %) in case of L. lecanii. Similar trends were also followed in neem oil and their 1:1 combination. Amongst all the vegetables, median lethal time (LT50) varied from 38.4 to 184.3, 33.7 to 172.8 and 30.6 to 149.2 h in case of L. lecanii, neem oil and their 1:1 combination, respectively. Lowest LT50 value was noted from of L. lecanii when P. solenopsis fed on okra and their ascending order of median lethal time was Okra > Pointed gourd > Tomato > Chilli > Cotton > Eggplant > Cucumber > Parthenium. Considering the median lethal time of mealybug reared on okra as base (1), time required for L. lecanii for 50 % killing of 6 ± 1 day old nymphs of P. solenopsis was 1.15, 1.38, 2.20, 2.72, 2.75, 2.90 and 4.80 times higher than when fed on pointed gourd, tomato, chilli, cotton, eggplant, cucumber and Parthenium respectively. From the present study, it is clearly evident that strong host mediated variations existed for susceptibility of P. solenopsis to L. lecanii, neem oil and their combination.