Seasonal activity of Helicoverpa zea and Heliothis virescens (Lepidoptera : Noctuidae) detected by pheromone traps in the rolling plains of Texas
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abstract
Bollworm, Helicoverpa zea (Boddie), and tobacco budworm, Heliothis virescens (F.), male moth activity were monitored for 15 yr (1982-1996) in sex pheromone traps in the Rolling Plains of Texas. The study consisted of 2 types of survey as follows: (1) weekly monitoring of bollworm and tobacco budworm moths in Hardeman and Knox counties to investigate their long-term seasonal activity patterns, and (2) daily monitoring of bollworm moths in Haskell, Knox, and Wilbarger counties to quantify the effect of lunar cycles on moth generation cycles. Moths were active from early April to late October, with increasing activity as the growing season of cotton, Gossypium hirsutum L., progressed through September. Although the bollworm-budworm complex in the region consisted of 93% bollworms and only 7% tobacco budworms, the seasonal trends in activity patterns were similar for both species. Correlation analyses showed a significant positive relationship between weekly trap catch and temperatures, but a significant negative relationship was observed between trap catch and wind velocity for both species. Although the average monthly activity levels were positively correlated between adjacent months, there was no significant correlation between the activity of the moth population that contributed to the overwintering generation and the following spring population. Mean seasonal abundance curves, with upper confidence limits, were constructed for each species based on 15-yr averages. The mean abundance curves of this type are useful for identifying years with unusual moth severity. Daily trap catch data showed that the moon phase influenced the capture of bollworm moths in pheromone traps, as indicated by a significant positive correlation between trap catch and percentage moon illumination. Daily trap catch data also showed that the maximum trap catch occurred 71% of the time during the full moon, followed by 1st quarter (11%), last quarter (9%), and the new moon (9%). However, the relationship between the trap catch and the lunar cycles was not apparent when the traps were serviced weekly, indicating the importance of sampling frequency in detecting the relationship between trap catch and moon phase.
