Position of the Uppermost White Bloom Defined by Node Counts as an Indicator for Termination of Insecticide Treatments in Cotton

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Abstract
Late in the season, the cotton plant ceases initiation of new branches, severely reduces fruit initiation on existing branches, and sheds many flower buds and small bolls. Plants exhibiting these characters are said to be cutout. The potential for additional harvestable bolls is restricted shortly before and after cutout. Management decisions to apply insecticides in late season should consider that many fruits will shed during plant cutout and that fruit already on the plants may not have sufficient growing conditions for maturation of fiber. One indication that plants are approaching cutout is white blooms on branches near the top of the plant. Use of the number of nodes between the uppermost white bloom and the first unexpanded mainstem leaf to assess cotton status and onset of cutout is described. The number of blooms retained (set) and the number of set blooms becoming harvestable bolls were summarized for intervals between average node counts. The interval between an average node count of four (rounded to nearest whole number) and the last bloom in a field had the lowest number of blooms, set blooms, and harvestable bolls than any other interval. The lint contribution to overall yield of harvestable bolls in the interval was estimated to be Heliothis spp. larvae and safe from severe attack by boll weevil, Anthonomus grandis grandis Boheman, adults. With our proposed procedure, insecticide would be applied as needed during a 10-day period for control of established Heliothis spp. larvae and during a 16-day period as needed for control of boll weevil adults after the field averaged four nodes between uppermost white bloom and first unexpanded mainstem leaf. Use of the node count procedure would be a valuable addition to cotton pest management programs through more cost-effective use of insecticides late in the season without a major loss of yield.