Biology, Ecology and Biocontrol Trials of Cotton Mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) in Sudan

Abstract

During 2012/ 2013 high infestation with mealybugs was recorded from different States of Sudan, on vegetables, fruits, ornamental plants and weeds; therefore, the objectives of this study were to investigate some aspects of this invasive pest in order to come out with effective strategies for its management. Surveys were conducted during the period 2015- 2019 to collect samples of mealybugs species in Khartoum State, and some other States in Sudan (Kassala, Gazira and Northern States ) for identification and afterward, studying the biology, host preference, seasonality and incidence of infestation, in addition to management by different control measures. All samples of mealybug collected were identified as Cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae). It was observed after the rainy season on Okra and on weeds, and migrates and become a source of infestation to the winter crops. From the results of the surveys, the population of mealybugs was high in March 2016 on tomato and egg plant (season 2015/ 2016) and low in Season 2016/ 2017 due to high rain fall. The biological parameters of P solenopsis were evaluated under laboratory conditions on four important crops: cotton (Gossypium sp), Okra (Abelmoschus esculentus), Tomato (Lycopersicon esculentus) and Sweet peper (Capsicum annuum), during the period January to April 2016. XVII The longest period of development for the female and male was observed on nymphs reared on cotton.the longest oviposition period and the average total fecundity were recorded on cotton and okra. For food preference of P. solenopsis , maximum population were recorded on plants of family Malvaceae at interval of 24 hours, particularly, on Okra, followed by cotton and hambouk as compared with the control (Hibiscus rosa-sinensis). While, the proportions were very low on unpalatable plants; raba and eggplant. In Sudan, a diversity of indigenous parasitoids and predators has been reported associated with mealybugs. Two of which were chosen: the Predator, Exochomus nigromaculatus (Goeze) (Coleoptera: Coccinellidae) and the parasitoid, Aenasius arizonensis (Girault) (Hymenoptera,Chalcidoidea).Their biological chararcteristics were studied to evaluate their effectiveness as a successful biocontrol agents of P. solenopsis . From the results, Predator, Exochomus nigromaculatus consumed and preferred the 3rd instar nymphs of P. solenopsis (when fed on a mixed diet of the 3rd and adult females). The coccinellid females consumed more prey than males and the 4th instar grub. From the results, the parasitoid, Aenasius arizonensis was available most of the year. It was highly effective on adults and the 3rd instar nymph of P. solenopsis, with a total percent parasitism of 31.26% XVIII in the field, and 20 to 24 in terms of number of Parasitized host female / day under laboratory conditions. The botanical insecticides Kafur, Eucalyptus camaldulensis,was evaluated against P. solenopsis using four concentrations (2.5%, 5%, 7.5% and 10%) . The highest percent mortality of Eucalyptus essential oil extracts was obtained by the topical method; where Ethanol extracts gave 100% mortality, followed by petroleum ether extracts, and lowest mortalities recorded from the aqueous extracts for both topical and dipping methods. The total life cycle of Cotton mealybug ranged from 21 to 39 days for female and 16 to18days for male, according to the host plants. Family Malvaceae was the most preferred and play an important role towards pest maturity and oviposition. The present study confirmed that, the natural enemies studied, have a potential future in pest control if subjected to further studies. In addition, more research is needed to identify the main active ingredients in the different parts of Eucalyptus tree.