Cotton Bollworms: Male Moth Catches in Pheromone Traps and Relationship to Oviposition and Boll Infestation in Cotton Fields in Middle Egypt

X.F. Gergis and A.M. Younis


 
ABSTRACT

Pheromone-baited traps are an important sampling tool in integrated pest management programs. Studies were conducted to determine the relationship between cotton bollworm male moths and the egg counts or larval infestation of cotton fields. When the correlations were constructed by relating the data from single or few separate traps in small size cotton fields to the egg counts and larval infestation around a single trap, the resultant linear regression models showed poor correlation coefficients (rcorr) between male moth catches and the studied variables.

After field evaluation of these mathematical models, data appear somewhat confusing and the higher values for root mean square deviations between the true field data and the expected (predicted) data, clearly indicate the failure of these models or at least their inadequency for simulating the field-collected data. Thus, scheduling treatments on the basis of these relationships in fact is not feasible.

Small field size, interfield movements, competition between the synthetic pheromone in traps and natural calling of bollworm females, immigration from outside the experimental fields and plant phenology, as well as the relative variation in the potential impact of the natural enemy complex among different cotton fields may have obscured these relationships. To avoid these problems, a relatively large number of traps were used in commercial-type growing cotton fields. Therefore, a direct relationship and highly significant correlations were obtained between the male moth catches and egg counts or larval infestations as well as other variables.

Field validation for these relationships proved higher in accuracy for simulating the actual data with negligible values of root mean square deviations. spiny bollworm and American bollworm in comparison to pink bollworm showed relatively lower values for correlation coefficients because the cotton was not the only host for them with considerable area growing alternative host plants inside the cotton fields.



Reprinted from 1993 Proceedings Beltwide Cotton Conferences pp. 1048 - 1051
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998