Helicoverpa zea (Lepidoptera: Noctuidae) Pupa Production in Fruiting Com in Northeast Mexico and South Texas

Populations of corn earworm, Helicoverpa zea (Boddie), pupae produced in ≍200,000 ha of corn growing in the Lower Rio Grande Valley of northeast Tamaulipas Mexico and south Texas were estimated. Pupae were excavated from two soil samples (1m2) in 90–120 cornfields each year between 1985 and 1988 following larval development on ear-stage corn. Mean plant populations in the fields ranged from 5.6 per meter of row in 1987 to 6.8 per meter of row in 1986, while ear infestation by H. zea larvae ranged from 76.9% in 1987 to 93.6% in 1986. The total number of corn earworm prepupae, pupae, and exuviae excavated ranged from an average 1.1 insects per square meter in 1987 to 3.8 insects per square meter in 1985. Correlation analysis indicated that only 58% of the variation in the number of corn earworm excavated from the 1-m2 soil samples was correlated with the variation in the number of infested plants per meter of row. Estimates of the number of live pupae produced from 200,000 ha of ear-stage corn in the Lower Rio Grande Valley ranged from 1.48 × 109 in 1987 to 7.16 × 109 in 1985. The potential for adult H. zea populations emerging from ear-stage corn to affect other crops subsequently is discussed.