Relation of Seasonal Changes in Extrafloral Nectar and Foliar Protein and Arthropod Populations in Cotton 1

Abstract

Insects found to feed on cotton extrafloral nectar included Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), Geocoris pallens Stål (Hemiptera: Lygaeidae), Orius tristicolor (White) (Hemiptera: Anthocoridae), Collops vittatus (Say)(Coleoptera: Melyridae), and Notoxus calcaratus Horn (Coleoptera: Anthicidae). The maximum volume of extrafloral nectar was produced in late July. Soluble solids in the nectar and percentage protein in the foliage were highest in young plants and decreased as the plants matured. Western flower thrips were abundant in flowers from late July to mid-Aug. The thrips population decreased when the last bolls set and nectar production and foliar protein levels were low. A small population of western bigeyed bugs was found on cotton throughout the season. The predators fed on thrips but did not show a pronounced numerical response to increases in the prey population. Bigeyed bugs were found to use extrafloral nectar as an alternate food. These observations uphold the concept that cotton extrafloral nectaries support small predator populations that protect the plant from phytophagous insect attack. Spider mites became abundant in Aug. and the mite population increased even though the protein content of the leaves was decreasing. Minute pirate bugs fed on both thrips and nectar, but the number of predators only increased after the mite population increased.