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Intensive surveys conducted at Samaru and its environs in the northern Guinea Savanna of Nigeria between October 2000 and September 2002, indicated that Bemisia tabaci (Genn.) infests forty two (thirty three cultivated and seven wild) species of plants. Twenty nine of the plants were found in upland, two in the lowland and eleven in both upland and lowland (fadama) areas. Heavily infested plants were distorted, chlorotic and stunted. Symptoms of virus infection were associated with some of the infested plants. This is the first comprehensive report of hosts of B. tabaci in Nigeria.
In addition to direct mortality caused by insecticides, some biological traits of insects may also be affected by sublethal insecticide doses. In this study, we used the age-stage, two-sex life table method to evaluate the sublethal effects of the four synthetic insecticides: abamectin, imidacloprid, diazinon, and pymetrozin as well as the botanical insecticide taken from Calotropis procera (Asclepiadaceae) extract, on eggs of the cotton whitefly, Bemisia tabaci (Hem.: Aleyrodidae). The lowest and highest survival rates and oviposition periods were observed in whiteflies treated by diazinon and imidacloprid, respectively. We found significant differences in the net reproductive rate (R0), the intrinsic rate of increase (r), the finite rate of increase (?), and the gross reproductive rate (GRR) among different insecticides. Altogether, our results showed that pymetrozin and C. procera induced the most sublethal effects, thus they may be suitable candidates for use in integrated pest management programs of B. tabaci.
The sweet potato whitefly, Bemisia tabaci (Genn.) (Biotype A: Hem.: Aleyrodidae) is one of the most important pests in Iran. The development of alternative methods that are not chemical applications, is necessary in pest management for the sake of human health and for the safety of the environment. In this research project, the effect of four herbal compounds Fumaria parviflora Lam. (Fumariaceae), Teucrium polium L. (Lamiaceae), Calotropis procera (Willd.) R. Br. (Asclepiadaceae), Thymus vulgaris L. (Lamiaceae) on the same biological parameters of cotton whitefly were compared with the insecticides azadirachtin and pymetrozin. The results showed significant differences between herbal compounds and insecticides on: egg longevity (F6, 39 = 2.96, p < 0.05), pupa longevity (F6, 37 = 4.49, p < 0.01) and adult longevity (F6, 31 = 4.47, p < 0.01); egg mortality (F6, 39 = 6.71, p < 0.001), total egg mortality (F6, 39 = 6.71, p < 0.001), sex ratio (female) (F6, 30 = 3.49, p < 0.01), oviposition period (F6,31 = 7.50, p < 0.001) and total fecundity/female (F6, 31 = 8.23, p < 0.001). These results indicated that a fumitory extract and pymetrozin had the best effect on longevity and mortality, respectively. According to the results, the fumitory had a noticeable effect on the different life stages of the sweet potato whitefly.
A survey in four distant locations: Anuradhapura, Madampe, Sri Jayewardenapura and Uda Walawe of Sri Lanka to identify the whitefly species related to cassava revealed two species, namely Bemisia tabaci (Gennadius) and Alerodicus dispersus (Russell). The species B. tabaci was recorded in all four surveyed locations, while A. dispersus was collected only from the first three locations. The results of the study on the pest life cycle under the laboratory conditions showed that, B. tabaci and A. dispersus passed through four nymphal instars before the adult stage. The mean duration values of these stages were 7.2, 7.5, 4.7, 5.6 and 8.5, 6, 9, 9 days respectively for the two species. The total duration of the life cycle of B. tabaci ranged from 22-57 days at the temperature of 29±2°C with a mean of 37.5 while that of A. dispersus was 27-68 days with a mean of 48 respectively (at 28±2°C). The damage to crop plants caused by two whitefly species is discussed with a special emphasis on their ability to transmit viral diseases.
The effects of application of an artificial honeydew mixture of glucose, fructose and trehalose (GFT), honey and Bemisia tabaci nymph-extract as kairomonal sources in enhancing the foraging efficiency and performance of Eretmocerus sp. near furuhashii on cucumber plants were studied. Experiments were conducted in small greenhouses (4x3*3 m) using life table methods. Life table data indicated that the total mortality in B. tabaci immature cohorts in all treatments was in the order of fourth instar > first instar > second = third > egg > pupa cohorts. The tested kairomonal materials had a significant effect on the rate of parasitism (p > 0.0415) with 13.23, 9.04 and 10.54% higher than that of control in artificial honeydew of GFT, nymph-extract and honey treatments, respectively. B. tabaci egg/adult survival ratio was also significantly affected (p > 0.0001) by the tested kairomonal sources being lowest (22.91%) in nymph-extract treatment. Moreover, the tested kairomonal materials arrested significantly more parasitoids to colonize the treated plants comparing to control. Apparently, the tested materials were significantly effective in attracting the parasitoids up to 3 days after applications then significant difference was not found between treatments.
This study assessed the insect pest infestation of tomato during 2011 and 2012 in three localities namely Bula Kuliye, Kajeri and Soye of Bama Local Government Area, Borno State, Nigeria. Fifty plants were randomly checked per farmers’ field for insect pest recovery and count. Sampling was carried out in five to nine farmers’ fields per locality. With 38-52 %, 9-62 %, 13-39 % and 5-9 % species composition respectively across localities, Helicoverpa armigera Hubner (Lepidoptera: Noctuidae) followed by Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) were more predominant insect pests of tomato in these localities over Tetranychus sp. (Acari: Tetranichidae) and Spodoptera litoralis (Boisd.) (Lepidoptera: Noctuidae). Total proportion of infested tomato plants per farmers’ field ranged from 19-36 %, and was significantly higher in Bula Kuliye and Kajeri than in Soye. Total number of insect pests per plant/leave and bored fruits per farmers’ field fell between 2-5 and 21-35, and likewise, was higher in Bula Kuliye and Kajeri than in Soye. Although tomato plant infestation and fruit damage were found to be moderate or high in these localities, future studies on the bionomics or population dynamics of these insects remain essential for establishing their economic status.
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