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End date: 2009Subject: search.filters.subject.Temperature

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    Functional response of Orius albidipennis (Hemiptera: Anthocoridae) to Megalurothrips sjostedti (Thysanoptera: Thripidae)
    (Karatina University, 2002-05-02) Gitonga (a), Linus M.; Löhrb (b), B.; Magambo (a), J. K.; Mueke (c), J. M.
    A locally available anthocorid predator, Orius albidipennis Reuter, was evaluated as a candidate biocontrol agent for Megalurothrips sjostedti Trybom, a major pest of French beans, Phaseolus vulgaris (L), in Kenya. The functional response of adult O. albidipennis to larval and adult M. sjostedti was studied at 15, 25, and 28 °C and densities of 5, 10, 20, and 30 larval and adult M. sjostedti per cage, over 24 h. More larvae and adult M. sjostedti were killed at the higher densities and with an increase in temperature. The data provided good fit to both type I and II functional response models. Attack rates increased with temperature for both the second instar larva and adult M. sjostedti. Handling times for the larvae decreased with an increase in temperature while those for the adults increased with increase in temperature. The implications of these results are discussed.
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    EFFECTS OF WEATHER ON THRIPS POPULATION DYNAMICS AND ITS IMPLICATIONS ON THE THRIPS PEST MANAGEMENT
    (Karatina University, 2008-06-30) Waiganjo, M.M.; Gitonga, L.M.; Mueke, J.M.
    Onion thrips, Thrips tabaci Lindeman, is the most destructive insect pest of the onion crop, Allium cepa L. worldwide. Both larvae and adults attack the onion crop at all stages of its growth, resulting in reduction of yield and quality. Despite the heavy losses incurred as a result of damage by the onion thrips, very little efforts have been made to develop an integrated pest management strategy for the control of the pest in many African countries. Field trials were conducted in four seasons at the Kenya Agricultural Research Institute (KARI) Mwea-Tebere farm in Kirinyaga District. Onion plants were planted periodically and thrips populations monitored weekly from onion plant samples and blue sticky traps for a full year under natural field conditions. The purpose of the trials was to assess the effect of weather on thrips population in onions with the aim of predicting thrips control requirements for a given climatic trend. Weather variables monitored included: rainfall, temperature, relative humidity and wind. Thrips occurred in the onion field and infested onions in all the crop seasons. However, there was significant (P=0.05) variation in thrips numbers between the crop seasons. Dry weather (30.3 mm rainfall) with moderately high temperatures (15.6-28.2oC) increased seasonal thrips numbers, while wet season (391mm rainfall) with moderately high relative humidity was negatively correlated with thrips numbers. Regression analysis (step-wise selection model) showed that minimum relative humidity was the only significant weather factor for predicting thrips infestation in the onion crop (R2 =0.15; y = 60.342-0.1022x). The results suggest that climatic trends can be used to determine the potential thrips control needs in onion production.
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    Functional response of Orius albidipennis (Hemiptera: Anthocoridae) to Megalurothrips sjostedti (Thysanoptera: Thripidae)
    (Karatina University, 2002-05-02) Gitonga, Linus M.; overhalt, W.A.; Löhr, B.; Magambo, J. K.; Mueke, J. M.
    A locally available anthocorid predator, Orius albidipennis Reuter, was evaluated as a candidate biocontrol agent for Megalurothrips sjostedti Trybom, a major pest of French beans, Phaseolus vulgaris (L), in Kenya. The functional response of adult O. albidipennis to larval and adult M. sjostedti was studied at 15, 25, and 28 °C and densities of 5, 10, 20, and 30 larval and adult M. sjostedti per cage, over 24 h. More larvae and adult M. sjostedti were killed at the higher densities and with an increase in temperature. The data provided good fit to both type I and II functional response models. Attack rates increased with temperature for both the second instar larva and adult M. sjostedti. Handling times for the larvae decreased with an increase in temperature while those for the adults increased with increase in temperature. The implications of these results are discussed.