THE ROLE OF GREEN PEACH APHID FLIGHT IN THE EPIDEMIOLOGY OF POTATO LEAFROLLDISEASE IN THE COLUMBIA BASIN

Authors: Thomas, Peter; PIKE, KEITH - WSU; REED, GARY - OSU

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Interpretive Summary This research indicates that dissemination of potato leafroll virus (PLRV) in the Columbia Basin of the northwestern USA depends almost exclusively on one aphid species, the Green Peach Aphid, which is dispersed seasonally throughout the region in three distinct and highly predictable migratory flights. Thus, control strategies, either chemical or biological, may be targeted on this aphid species, on its dispersal flights, and on the sources of virus disseminated by this aphid. The spring flight from the overwintering host, peach, rarely, if ever, introduced virus into potato fields from outside sources, but this flight colonizes potatoes, and its wingless progeny rapidly disseminated virus from seed sources of virus already in the field. The summer flight did introduce PLRV into potato fields from outside sources. Thus, use of pesticide to control aphids could be delayed until after the summer flight if seed potatoes could be obtained that were free of potato leafroll virus. Only one or two pesticide applications would be needed to finish the crop. This could eliminate the use of a substantial portion of the millions of pounds of insecticide currently used to control potato leafroll disease in the Columbia Basin. As an alternative to pesticide, biological control strategies implemented in late June or early July to focus on the mid- summer flight might be more effective in potatoes where an earlier application of insecticide, used to control the spring aphid flight, had not eliminated aphid predators and their food source.

Technical Abstract: Technical Abstract Three distinct and highly predictable green peach (GP) aphid (Myzus persicae Sulzer) migrations (flights) that occur seasonally in the spring, summer, and fall were detected at a southern, central, and northern location in the Columbia Basin of Northwest United States. Intensity and timing of the flights was approximately the same at the three locations. Timing and number of alatae captured in the spring, but not the summer, flight was closely associated with heat unit accumulation. The spring flight, which originates on the overwintering peach tree host, colonized but did not introduce potato leafroll virus (PLRV) into virus-free potato plots. The summer flight, which originates from volunteer potatoes and spring herbs originally colonized by the spring flight, did introduce PLRV into virus-free potatoes. The fall flight was too late to affect potato production. Apterous progeny of spring flight alatae rapidly spread point sources of PLRV already present to all plants in the plots in a plant-to- plant mode. Rate of spread from point sources of infection was not affected by timing or intensity of the spring flight, but timing of virus spread in the plots depended on time of arrival of the aphids. Once PLRV was introduced to virus-free plots by the summer flight, virus spread to other plants within the plots. GPA overwintered on peach trees. Although GPA apterae and alatae were present on winter annual weed and crop hosts in the fall, none survived winters on these species. In addition to the GPA, one other vector of PLRV, Macrosiphum euphorbiae (Thomas), was rarely collected in aphid traps. These results suggest chemical control of aphids could be delayed until mid-July if PLRV-free potato seed were available.