Effect of aphid control on the spread of leafroll in potatoes

Summary

Four applications of 10 insecticides were made with a power ground duster to Netted Gem potatoes planted for early and late crops at Yakima, Washington, to determine their relative values for controlling the green peach aphid (Myzus persicae (Sulz.)) and the potato aphid (Macrosiphum solanifolii (Ashm.)) and, indirectly, for preventing the spread of potato leafroll.

In experiments 1 and 2, on potatoes planted for an early crop, dusts containing 4 per cent of DDT and 80 per cent of sulfur, 5 per cent of DDT and 75 per cent of sulfur, or 5 per cent of DDT all gave good control of aphids and the incidence of leafroll did not exceed 5.8 per cent. Aphid populations were highest where 33.3 per cent of sodium fluoaluminate dust was used, and on those plots the leafroll incidence was 23 per cent.

In experiment 3, on potatoes planted for a late crop, the highest aphid population was again found in plots that had received 33.3 per cent of sodium fluoaluminate dust, and the leafroll incidence was 61.3 per cent. Five per cent of DDT, and 3 and 5 per cent of DDT with 2 per cent of oil were also relatively ineffective for aphid control, and the leafroll incidence was 49 to 57.4 per cent.

A dust containing 5 per cent of DDT and 75 per cent of sulfur gave the best control of aphids throughout the entire season, and the incidence of leafroll was 43.1 per cent. Dusts containing parathion were relatively ineffective during the period of extensive winged-aphid migration; consequently leafroll transmission was high during this period. However, parathion gave good control after the migration had abated and leafroll incidence did not exceed 43 per cent. DDT-sulfur and parathion dusts were equally effective in preventing the spread of leafroll.