Efficient and economical kaolin concentration for cotton protection against boll weevil

Abstract

The objective of this work was to determine the most effective and economical kaolin concentration to protect cotton against the injuries caused by the boll weevil (Anthonomus grandis). A randomized complete block design was used with five treatments of kaolin spraying at the following concentrations: 20, 40, 60, 80, and 100 g L^-1. The following parameters were determined: percentage of punctured squares with oviposition by boll weevil females; the amount of kaolin residues on leaves and bracts of cotton square; average yield; and the cotton net income per hectare, measured from the weighing of cotton lint with seed. The percentages of oviposition‑punctured squares ranged from 13.6 to 30.8%; kaolin residue, deposited on cotton leaves, ranged from 0.0010 to 0.0034 mg mm^-2, and on bracts, from 0.0010 to 0.0034 mg mm^-2; production ranged from 348.1 to 717.8 kg ha^-1; and the net revenues from cotton ranged from R$ 1,033.88 to R$ 2,098.86 per hectare. The most efficient kaolin concentrations for cotton protection against damage caused by boll weevil are those of 60, 80, and 100 g L^-1; however, the concentration of 60 g L^-1 is the most economic one.