MSc

Pineapple mealybug (Dysmicoccus brevipes) causes severe damage to pineapple crop in Kerala. Apart from the direct damage and it also transmits Pineapple Mealybug Wilt Disease (PMWD). This is a polyphagous pest and its host includes banana, coffee, citrus, palm, sugarcane etc. Use of broad spectrum synthetic insecticides to manage the mealybug has been restricted owing to the residual problem in the fruit and other environmental concerns. Hence, the present study, “Eco-friendly management of pineapple mealybug, Dysmicoccus brevipes (Cockerell) (Hemiptera: Pseudococcidae)’’ was carried out at Department of Agricultural Entomology, College of Horticulture, Vellanikkara, during September 2014 to June 2016, with the objectives to document the natural fauna of Dysmicoccus brevipes and to formulate eco-friendly measures for managing the pest polulation Laboratory rearing of D. brevipes was done on pumpkin fruits. The mealybugs reproduced parthenogenetically. Males were absent in the population.Life cycle of females consisted of three nymphal instars and adult stage. The mean duration of first and second nymphal instars were 10.8 and 13.7 days, respectively. The average third nymphal instar period was 15.6 days. Adult
females lived for an average of 23.2 days with pre-larviposition, larviposition and post-larviposition period of 8.7, 4.5 and 9.8 days, respectively. An adult female deposited an average of 144.5 crawlers. The total life cycle completed within 63.4
days. Number of antennal segments varied among each instars. The first and second instar nymphs had six antennal segments each while third instar nymphs and adult possessed seven and eight antennal segments respectively. To document the natural enemies of D. brevipes, purposive survey was done in selected locations of Ernakulam, Idukki and Thrissur districts. The natural enemies recorded included four predators [Spalgis epius (Westwood), Cacoxenus perspicax (Knab) and two unidentified species of Scymnus] and one parasitoid (Chartocerus sp.).
Three species of Entomopathogenic fungi (EPF) viz., Metarhizium anisopliae, Beauveria bassiana and Lecanicillium lecanii were evaluated at three different concentrations (1x107, 1x108 and 1x109 spores ml-l) under laboratory conditions against D. brevipes. Highest spore concentration of all the
entomopathogenic fungi resulted in higher mortality of mealybugs. L. lecanii @ 1x109 spores ml-l concentration had resulted in 66.67 per cent mortality. Similarly, in case B. bassiana and M. anisopliae @ 1x109 spores ml-l concentration mortality of 60 and 40 per cent, respectively was observed.
In pot culture studies, the best performing concentration of EPF from the laboratory assay was evaluated along with a botanical insecticide and a standard check (quinalphos 25EC @ 0.05%). Ten days after the first treatment application, highest reduction was observed in quinalphos (96.73%) followed azadirachtin
(87.75%). Among the three EPF tested, M. anisopliae caused the maximum reduction of (59.29%) of mealybug. Similarly, second spray of M. anisopliae and B. bassiana recorded maximum reduction of 72.72 and 70.98 per cent, which
were statistically on par with each other. After the third spray, L. lecanii resulted in highest reduction (90.04%) of mealybugs which was on par with the reduction obtained by quinalphos (95.20%) application. Infestation of Dysmicoccus brevipes induced changes in pineapple fruit quality and it was estimated by quantifying the Total Soluble Sugars (TSS), content of the fruit at varied level of infestation. Fruits with heavy infestation of
mealybugs showed less TSS content (8.74° brix) compared to the TSS level in medium and low infestation (9.93° brix and 11.31° brix, respectively).