D. L. Coudriet

Population dynamics and control strategy for Bemisia tabaci in the imperial valley, California☆

Abstract Bemisia tabaci (Gennadius) populations were monitored in 1983 in the Imperial Valley of California on cotton and alfalfa utilizing yellow sticky traps and leaf samples. The influence of B. tabaci populations on cotton and early defoliation of cotton on autumn-planted crops was discussed. Infrared aerial photography was used as a survey tool to locate high whitefly densities in cotton. Insecticide resistance, adverse effects of pesticides on beneficial arthropods and different developmental rates on cultivated crops were factors that enhanced B. tabaci population increases.

Effect of Three Insect-Borne Virus Diseases on Sugar Beet Seed Production

Tests to determine the effect of beet yellows and beet western yellows on sugar beets grown for seed were conducted in field plots From 1959 to 1962. The effect of these diseases, alone and in combination with each other and with curly top, was tested. Green peach aphids ( Myzus persicae (Sulzer)) were used as vectors of the yellows viruses and beet leafhoppers ( Circulifer teneltus (Baker)) as vectors of the curly top virus. Both beet yellows and beet western yellows reduced seed yields but did not affect germination. Mixtures of the two yellows viruses caused much greater losses than either one alone, and early infections reduced yields more than later infections. Early spring yellows infection of curly top-resistant beets inoculated with curly top in the fall did not reduce yields more than yellows alone. Spring infection of curly top-susceptible beets with curly top virus had no measurable effect on the seed crop, but when followed by yellows infection, losses were greater than with yellows alone.