Studies of Ostrinia nubilalis Larvae (Lepidoptera: Pyraustidae) on Corn Plants Supplied with Various Amounts of Nitrogen and Phosphorus. I. Survival12

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Abstract
Survival of first- and second-generation Ostrinia nubilalis (Hübner) larvae on susceptible WF9×M14 and resistant Oh43×Oh51A corn hybrids was determined about 30 days after egg hatch. In 1 set of experiments the plants in gravel culture were supplied with nitrogen concentrations of 10 to 300 ppm; and in another set, with phosphorus concentrations of trace to 80 ppm. Survival of first-generation larvae on the susceptible hybrid was 10-fold greater at 200 ppm than at 10 ppm nitrogen. Survival on the resistant hybrid was low and not affected by the amount of supplied nitrogen. Few larvae survived on plants of either hybrid that received 2.5 ppm or less phosphorus; survival at 10 ppm was triple that at 2.5 ppm, but did not improve at concentrations of 20–80 ppm. Field studies showed also that survival was influenced by the amount of phosphorus in the soil. Leaf-feeding damage and number of leaf lesions and tunnels were equally as effective in determining the effect of nitrogen or phosphorus on survival as were the numbers of surviving larvae. The factors that caused the difference in survival on plants that received different nutrient treatments appeared to be operative when the larvae were in the first and second instars. Second-generation larvae survived equally well in 1958 on susceptible plants supplied with 50–300 ppm nitrogen. In 1959, survival was best on susceptible plants given 300 ppm and on resistant plants given 100 ppm nitrogen. Survival was best on susceptible plants that received 10 ppm phosphorus, but was not consistently high on resistant plants at any single phosphorus level. With both first and second generations on the same plants, the greatest number of larvae found in the fall were on plants of both hybrids that received 200 ppm nitrogen. No difference in survival was found on plants given from 5 to 80 ppm phosphorus, but in tests of trace to 10 ppm, survival was highest at the 10-ppm level.