Greenhouse and field studies were conducted to evaluate possible mechanism of resistance of three sunflower hybrids (Cargill 187, Cargill 120, and Hybrid 894) to sunflower midge, Contarinia schulzi Gagné. The hybrids were seeded on two dates each year at Mapleton, ND in randomized complete block with 6 replicates. Each replicate consisted of five 3 m row of each hybrid and a row of buffer between replicates. Plants sampled were randomly selected from the inside rows of each replicate. Estimated egg and larval populations and damage ratings were used to quantify the mechanisms of resistance. All three resistance mechanisms were present. Antixenosis to oviposition was detected as a reduced number of eggs. Antibiosis was also present as low larval survival. Low damage per larva indicated tolerance.
Species 1: Diptera Cecidomyiidae Contarinia schulzi (sunflower midge)
Keywords: resistance mechanism, host plant resistance
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