ARS | Publication request: DISTRIBUTUION OF HAIRY NIGHTSHADE IN MAINE POTATO AGRO-ECOSYSTEMS AND POTENTIAL RISKS OF INFECTION BY PHYTOPHTHORA INFESTANS

Submitted to: Northeast Potato Technology Forum Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2006
Publication Date: March 25, 2006
Citation: Olanya, O.M., Plant, A.B., Larkin, R.P., Lambert, D.H. 2006. Distributuion of hairy nightshade in maine potato agro-ecosystems and potential risks of infection by phytophthora infestans. Northeast Potato Technology Forum Abstracts. CD-ROM

Technical Abstract: The occurrence of hairy nightshade (Solanum sarrachoides) as an alternate host of Phytophthora infestans can impede current late blight management options by providing undetected refuges and sources for inoculum dissemination to potato crops. To evaluate the significance of hairy nightshade as a host of P. infestans and potential threat to potato production, we assessed the distribution of hairy nightshade in potato fields and determined infection rates, inoculum levels, plant growth stage, temperature, and relative humidity (RH) effects on progress of late blight on hairy nightshade. Infection rates of hairy nightshade incited by P. infestans were significantly lower (P<0.05) than on potato and tomato hosts. Late blight levels varied with inoculum amount, and susceptibility of hairy nightshade increased with plant age from 2 to 8 weeks. Late blight progress on hairy nightshade was greater at 18 and 22 C than at 14 or 26 C, whereas foliage blight severity was similar at 72 to 92% relative humidity values at 22 C. The growth stages of nightshade plants in potato fields were variable and within field spatial pattern of the weed was aggregated. The occurrence of hairy nightshade weed was closely linked to cropping pattern or history. These results imply that nightshade can be infected at various stages of growth regardless of the inoculum amount. Late blight development on S. sarrachoides at various RH, temperature ranges, and low rates of disease progress suggest a longer duration for inoculum production and high risk of late blight potential.