Lethal and sublethal effects of neem leaves extract (Azadirachta indica) against pink hibiscus mealy bug (Maconellicoccus hirsutus) (Hemiptera: Psudococcidae)

Abstract

Maconellicoccus hirsutus, commonly known as the pink hibiscus mealybug, is a polyphagous insect pest with a global presence, posing significant economic and ecological threats to a wide range of host plants. This study evaluated the lethal and sub lethal effects of neem (Azadirachta indica) leaves extract against Maconellicoccus hirsutus under laboratory conditions. Adult female’s M. hirsutus were treated with dilutions of neem leaves and the greatest mortality (54%) was observed at 5% neem leaves extract after 72 hours, while no mortality was recorded in the control after 72 hours. The LC₅₀ value of 4.85 ppm of the neem leaves extract was calculated for female adult of M. hirsutus after 72 hours of exposer and was further tested on the fresh eggs and nymphs of M. hirsutus. Contact exposing of the eggs and nymphs to neem leaves extract significantly reduced the % hatch rate of M. hirsutus eggs (45.23%) and caused significantly high mortality of the nymph (62.22%) after 72 hours as compared with the control. The sub-lethal effect of the neem leaves extracts on the female adult of M. hirsutus showed that the insects treated with 5% neem leaves extract concentration had significantly lower values of finite rate of increase (λ) (1.09±0.004 day^-1), intrinsic rate of increase (r) (0.08±0.004 day^-1) and net reproductive rate (R_o) (32.56±4.75 eggs/female) as compared with the population treated with lower neem leaves concentrations. Similarly, the age-stage specific life expectancy (e_xj) and age specific reproductive value (v_xj) of M. hirsutus were recorded lower when treated with 5% neem leaves extract as compared to other treatments. This study revealed that neem leaves extracts are highly effective in reducing M. hirsutus infestation and can be used in mealybug IPM programs.