STUDIES OF BIOLOGY AND CONTROL OF RHOPALOSIPHUM PADI (L.) IN SELECTED WHEAT AND OAT CULTIVARS WITH SEED SYSTEMIC INSECTICIDES (CARBOFURAN, DISULFOTON, BYDV (BARLEY YELLOW DWARF VIRUS))
Abstract
Periodic collections of the bird cherry-oat aphid, Rhopalosiphum padi (L.), during two years revealed small populations on winter wheat in Lafayette, Indiana. The highest numbers occurred before planting, in volunteer wheat plants. In the crop, aphids were detected on one-shoot plants by mid October, and early March. The populations remained small until mid June. It is speculated the aphids did not significantly affect the plants, but may have spread barley yellow dwarf virus (BYDV). The life-cycle of the aphid was studied in the laboratory comparing individuals carrying BYDV (PAV isolate) and virus-free aphids. Sections of leaves of wheat cultivars 'Abe' and 'Caldwell', and oats 'Clintland 64' and 'Porter', infected with BYDV and virus-free, were used to rear the aphids in Petri dishes at 18 (+OR-) 1 C. Daily observations were made for prereproductive and reproductive periods, life duration, adult life, total number of progeny produced, mean progeny production, and mean number of nymphs per day during the reproductive period in all treatments. The data were analyzed for each crop by ANOVAs. The Student-Neuman-Keuls' test was used to separate means (P (LESSTHEQ) 0.05). The aphids had a shorter lifespan and adult life on virus-infected wheat. There were also differences for life duration between wheat cultivars x BYDV-infection. Virus-infection increased the reproductive capacity of the aphid in wheat, but not in oats. Further studies are needed to clarify the epidemiological relationships of BYDV, its vectors, and plant cultivars. Laboratory tests with carbofuran and disulfoton treated seeds showed the aphid mortality related to the dosage, with differences between cultivars. Standard dosages (1000 ml AI/100 kg seed) protected the plants from 2 to 4 weeks. Longer residual effects were obtained in wheat than in oats. Carbofuran did not affect germination. Increasing dosages of disulfoton were progressively more toxic (probably in part because of the organic solvent of the formulation).
Degree
Ph.D.
Subject Area
Entomology
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