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Adequacy of 100 Square per Field Sampling Technique for Estimating Damage by Boll Weevil (Coleoptera: Curculionidae) Heliothis Virescens (F.) And Helicoverpa Zea (Boddie), (Lepidoptera: Noctuidae) in an Area Wide Cotton IPM Program

Dan A. Wolfenbarger and J. W. Norman, Jr.


 
ABSTRACT

In 1973-75, a sample size of 100 fruiting forms (=squares (flower buds) or small bolls) of cotton per field in the Lower Rio Grande Valley of Texas was used to estimate damage by the boll weevil, Anthonomus grandis Boheman, and either or both bollworm Helicoverpa zea (Boddie), and tobacco budworm, Heliothis virescens (F.). Sampled fruiting forms were tabulated as damaged or undamaged by the boll weevil or the lepidopteran species. Sampling for boll weevil and bollworm/tobacco budworm in each field each year was conducted twice a week in an "X" configuration across conditions of both dryland and irrigated fields. In this area 15,000 to 20,000 fields are planted yearly. Number of fields to sample was determined by binomial distribution from the total number fields sampled on each day during all three years. This estimate for number of 100 forms/field to sample on each day was adequate when the number of times to sample was equal or less than the number of 100 forms/field actually sampled. Dryland cotton fields, with its lower levels of damage, required more intensive sampling than did irrigated cotton fields. Variance increased as mean damage level increased, indicating that mean and variance were directly related. This analysis was conducted to evaluate the efficacy of a sampling method presently used by the Texas Agricultural Extension Service in the LRGV.



Reprinted from Proceedings of the 1999 Beltwide Cotton Conferences pp. 1250 - 1254
©National Cotton Council, Memphis TN

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Document last modified Monday, Jun 21 1999