IDAHO APHID FLYER

Last Flyer

    Our plans are for this issue to be our last  for 2000. We will continue to run the suction traps for 2 more weeks. If we catch an up-surge in aphid populations, we will send another flyer. We will continue to survey fields this fall and monitor for aphid infestations. 

Suction Traps       

    The trap samples in the last two weeks have dropped considerably, with the exception of spotted alfalfa aphids in Parma which seem to be on the rise. Spotted alfalfa aphid is a smaller (¹/₁₀ inch long), more active aphid than pea aphid. It is pale green or yellow and has four to six rows of darker green spots on the upper abdomen, each tipped with a short hair. Spotted alfalfa aphids reproduce asexually; no males have been detected. Development of spotted alfalfa aphid is optimal when temperatures are between 80° and 90° F and humidity is low, with peak populations tending to develop late in the summer. Besides drawing photosynthetic material from the plant, this species injects a toxic substance into the plant, causing yellowing. This species feeds preferentially on older leaves lower on the plant, moving up as leaves die. Spotted alfalfa aphid feeding will cause yellowing under lower densities, because they inject a toxin into the plant. Seedling plants may be killed and older plants may grow slowly and be stunted. Under high densities of these species, growth is retarded, and the weakened plants may grow slowly after cutting. Invasion by weeds and general susceptibility to stress is increased; stand longevity may decrease after damage by aphids.

Fall Planting

         Populations of cereal aphids that are of concern continue to decline. If this trend continues, those growers, who’s normal planting window is in September, should not need to make any adjustments to normal planting practices.

                                         Funded by the University of Idaho Agricultural Experiment Stations and the Wheat & Barley Commissions.

Samples collected August 18 & 25, 2000