The role of host and host phenology in the population dynamics of the bollworm, Heliothis zea (Boddie), in the Brazos River Valley, Texas

Abstract

Field studies were conducted to identify the role of host and host phenology in the population dynamics of the bollworm with special emphasis on some of the factors determining the timing and magnitude of the infestations on cotton in the Brazos River Valley of Texas. The seasonal activity of the bollworm in com, sorghum, and cotton was determined using 40 w blacklight (EL) traps over a 3-year period (1973-75). Based on the acreage in each crop and the observed moth activity, it was evident that sorghum was the crop which contributed the most adults for the subsequent infestation of cotton; however, it was also found that c o m was the apparent source of the adults comprising the initial infestation. Most adult bollworm activity during the early season which was mainly confined to corn and sorghum, was characterized by greater catches of males than of females in the BL traps. Full moon appeared to be associated with increases in female catches when male catches were high. Starting in the latter part of June or in July, similar numbers of males and females were generally caught in all 3 crops and the periods of lowest adult activity were generally associated with full moon. Individual silks were found to be at peak attractiveness for oviposition 3 days after silk emergence; however, attractiveness did not decrease greatly until 6 days postemergence. Peak oviposition by bollworm moths in corn fields occurred during flowering and generally coincided with peak silking and not with maximum numbers of 3-day old silks. The preferred ovipositional sites during silking were the silks, but prior to silking, the upper leaf surfaces were preferred..