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Title: INTERACTION OF COLLETOTRICHUM ORBICULARE WITH THRIPS AND APHID FEEDING ON WATERMELON SEEDLINGS

Author
item Russo, Vincent
item RUSSO, B - OKLAHOMA STATE UNIVERSITY
item PETERS, M - OKLAHOMA STATE UNIVERSITY
item Perkins Veazie, Penelope
item CARTWRIGHT, B - OKLAHOMA STATE UNIVERSITY

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/27/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Crops can be parasitized by organisms, and the outcome on plants is determined by the interaction of all those involved. Time of infestation, in relation to time of infection, can affect the outcome of disease development on watermelon (Citrullus lanatus). Seedlings were untreated, inoculated only with the fungus Colletotrichum orbiculare (CO), infested only with thrips (Thrips tabaci) or aphids (Aphis gossypii), or infested before or after inoculation with CO. Effects on plant development (height and dry weight), and amount of area developing lesions were measured. The insects interacted differently with the plant and CO. With thrips as the insect component untreated plants and those infested after inoculation with CO were tallest. Untreated, CO only treated, and thrips only plants infested before inoculation with CO were heaviest. Percent necrotic area was similar for CO only treated plants and for plants infested after inoculation with CO, but less when infestation was before inoculation. With aphids as the insect component plant height and dry weight were not affected. Percent necrotic area on CO only treated plants was twice that of plants infested before or after inoculation with CO. A better understanding of these interactions can lead to improved control of insect or fungus pests.

Technical Abstract: Plant-microbe-insect interactions are not well understood, and affect development of the plant, microbe, or insect. Watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) seedlings were either untreated, inoculated only with the fungus Colletotrichum orbiculare (Berk. & Mont.) Arx (CO), infested only with thrips (Thrips tabaci Lindeman) or aphids (Aphis gossypii Glover), or infested before or after inoculation with CO. Plant heights and dry weights, and percent necrotic area on cotyledons, true leaves, and the whole plant (cotyledons and leaves) were determined over 5 planting dates in a greenhouse. Planting date did not affect results. With thrips as the insect component, untreated plants and those infested after inoculation were tallest. Untreated, CO only treated, and thrips only plants infested before inoculation were heaviest. In addition percent necrotic area on cotyledons, leaves, and the whole plant significantly reduced (P <0.05) on plants infested prior to inoculation with CO compared to plants receiving CO treatment only and plants infested after inoculation with CO. With aphids as the insect component, plant height and dry weight were not affected, and percent necrotic area on plants infested before or after inoculation with CO was significantly lower than on plants inoculated with CO only.