Publication: Effect of intercrops on thrips species composition and population abundance on French beans in Kenya
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2011-12-12
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Federal Ministry for Economic Cooperation and Development, through GIZ
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Abstract
The study aimed at determining thrips species composition and thrips population density on French
bean planted as a sole crop and as an intercrop with either sunflower, Irish potato, or baby corn, in
various combinations. Field experiments were conducted in two seasons to examine: (1) thrips population development and thrips species composition over time, (2) effect of intercrops on thrips population density and natural enemies, and (3) effect of intercrops on French bean yield. The
experiments were conducted at the Kenya Agricultural Research Institute, Embu, Kenya in a randomized complete block design with four replicates. The thrips population on French beans increased
with time. It showed a peak at the flowering stage then started declining when the crops were nearing
senescence. French beans hosted four thrips species, Megalurothrips sjostedti (Trybom), Frankliniella
schultzei (Trybom), Frankliniella occidentalis (Pergande), and Hydatothrips aldolfifriderici (Karny)
(all Thysanoptera: Thripidae) in order of decreasing abundance. The main thrips species on Irish
potato and sunflower was F. schultzei. Baby corn hosted only Frankliniella williamsi (Hood) and
Thrips pusillus (Bagnall). A monocrop of French bean hosted more thrips than a French bean intercrop mix. Thrips natural enemies such as Orius spp. and Ceranisus spp. were recorded in all crop
plants but in especially high numbers on French bean and baby corn, respectively. Plots with French
bean alone had about 1.4 times higher yields compared to intercropped plots of French bean with
sunflower and French bean with baby corn. However, the percentage of pods that could get rejected
on the market due to thrips damage was highest on plots with French bean alone (68 and 63%) and
lowest on plots with French bean and baby corn (35 and 37%) in the first and second seasons, respectively. This study showed that a complex of thrips is found in the field and its composition varies with
crop stage and species. Intercropping French bean with other crops compromises on French bean
yield but reduces damage to the French bean pods, thereby enhancing marketable yield.
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Keywords
Frankliniella occidentalis, Frankliniella schultzei, Hydatothrips aldolfifriderici, Megalurothrips sjostedti, intercropping, Thysanoptera, Thripidae, Fabaceae, Phaseolus vulgaris, natural enemies, associational resistance