Effectiveness of Some Plant Extracts Compared with Chemical Insecticides to Control Cochineal Scale Insect, Dactylopius opuntiae under Field Conditions

This study was conducted in 2021 in the Department of Plant Protection, Faculty of Agriculture, University of Damascus, and in the fields of Qatana region. Alcoholic and aqueous extracts of tobacco, Nicotiana tabacum L., eucalyptus, Eucalyptus camaldulensis D., chinaberry, Melia azedarach L. and aerial parts of amaranth, Tagetes patula L. were evaluated for the control of cochineal scale insect, Dactylopius opuntiae Cockerell (Hemiptera, Dactylopiidae) and compared with chemical insecticides: chlorpyrifos, dimethoate, and lambda-cyhalothrin, and Sycro (mineral oil). The results obtained showed that the aqueous extracts of the tested plants at concentrations of 2.5 and 5.0% had moderate to low effect against the different stages of the cochineal scale insect, D. opuntiae. Whereas alcoholic extracts at a concentration of 5.0% were highly effective against males and nymphs of the insect, and the effectiveness increased with time after treatment. The average effectiveness rate for the leaves extract of tobacco, chinaberry, amaranth, and eucalyptus plants reached 51.18, 46.25, 39.65 and 32.50% for males; 38.25, 27.15, 25.21 and 20.32% for nymphs, 5 days after spraying, respectively. Whereas the effectiveness of alcoholic extracts was moderate on female insects. On the other hand, both dimethoate and chlorpyrifos pesticides had the highest effectiveness on males, nymphs, and females of the cochineal scale insect, with significant difference with the rest of the treatments. Whereas the pesticide Lambda-cyhalothrin and mineral oil had a medium effect on the instars of the insect. The results also showed that the effectiveness rate gradually increased with increasing concentration and exposure period. Accordingly, alcoholic extracts of tobacco and astragalus can be recommended for the control of the cochineal scale insect as natural and safe pesticides. Keywords: Insecticides, Dactylopius opuntiae, plant extracts, chinaberry, tobacco.