Green Peach Aphid Alert
    It is time for everybody to get your boots muddy and start turning over potato leaves. Green peach aphids were found in a potato field in Cassia and Power counties on June 26. According to Dr. Jeff Miller growers should intensively scout fields for aphids at this time. Insecticide applications may be needed for varieties susceptible to net necrosis, particularly if insecticides were not applied at planting or at hilling. The usual scenario for these aphids seems to move from west to east. Green peach aphids are pale or bright green and black, with a large, dusky blotch on the dorsum of the abdomen. The immature forms are yellow, pinkish, or pale green. The mature, wingless forms are pale or bright green. These aphids are usually found on the underside of the lower leaves and the wingless forms are about the color of Mt. Dew soda pop.
      
Spotted Alfalfa Aphids
    The spotted alfalfa aphid is a small, pale yellow or grayish aphid with four to six rows of spined black spots on its back. Mature females may either be wingless or have wings with smoky areas along the veins. New seeding should be monitored closely for these aphids. The threshold for these aphids on new seeding is one per stem. Severe aphid infestations retard growth, reduce yield, and may even kill plants. Damage can also reduce the alfalfa's feed value. A black fungus that grows on the honeydew excreted by the aphid reduces palatability. 
    Aphid counts should be made by carefully cutting a stem close to the ground with a sharp knife, pulling up the cut stem, and then counting the aphids on the undersides of leaves. You can also rap it sharply against a stiff piece of white paper or into a white pan. This will dislodge the aphids and they can be easily counted. This procedure should be repeated, cutting a number of stems at several locations in the field. (While counting aphids, note the presence or absence of lady beetle larvae, parasitized aphid mummies, or aphids killed by fungus.) When inspecting individual stems on new regrowth alfalfa, it is important to pry open small, new leaves and search the spaces between them; many first and second instar nymphs can often be found there. In addition to monitoring aphid populations, also take sweep net samples for lady beetles. 

    .Bird cherry-oat aphid numbers are rising in most locations. Barley yellow dwarf virus is transmitted by cereal aphids (principally bird cherry oat aphid and, in the southeast Idaho high country, the greenbug). Barley yellow dwarf virus can cause 50-75% crop loss if all the plants become infected. More importantly, we use these aphid numbers as an indicator of the presence of wheat curl mites, which spread wheat streak mosaic virus. This problem seems to occur with higher bird cherry oat aphid populations. 

Funded by the University of Idaho Agricultural Experiment Stations and the Barley Commission.

Samples collected June 20, 2003

*Not running-broke