Because boll weevil, Anthonomus grandis Boh. develops partially protected inside cotton fruiting structures, once they become established in a field, they are difficult to control, even with nearly continuous insecticide spray. During two cotton-growing seasons in the Semiárido region of Pernambuco State, Brazil, we tested the use of kaolin sprays to disrupt plant colonization through visual cue interference, combined with removal of fallen fruiting bodies to restrain boll weevil population growth after colonization. Kaolin spray under non-choice trials resulted in 2.2×, 4.4×, and 8.6× fewer weevils, oviposition and feeding punctures on kaolin-treated plants, respectively, despite demonstrating no statistical differences for colonization and population growth. Early season sprays in 2010 occurred during a period of rainfall, and hence, under our fixed spraying schedule no significant differences in boll weevil colonization were detected. In 2011, when kaolin sprays were not washed out by rain, delayed boll weevil colonization and reduction on attacked fruiting bodies were observed in eight out of 12 evaluations, and kaolin-treated plots had 2.7× fewer damaged fruiting bodies compared to untreated plots. Adoption of simple measures such as removal of fallen fruiting bodies and prompt reapplication of kaolin sprays after rainfall show promise in reducing boll weevil infestation.

The objective of this study was to evaluate the effect of gaseous ozone on the physiological quality of corn seeds with different initial germination percentages. Seeds with initial germination percentages of 54.0% (low physiological quality) and 86.0% (high physiological quality) were used. Samples of 0.12 kg of seeds were exposed to different combinations of inlet ozone concentrations (10 and 30 mg L⁻¹) and exposure times (0, 30, 60, 90, and 120 min). A flow rate of 1.0 L min⁻¹ was used at a temperature of 25 °C. The percentage of germination, shoot, root, and seedling lengths, germination velocity index, and electrical conductivity were analyzed. Univariate and multivariate analysis were used for data analysis. Seeds with low initial germination percentage showed increase of 1.6 to 1.8 times in germination percentage and approximately 1.2 times in length of the seedlings when the inlet ozone concentration was 10 mg L⁻¹ and the exposure times were 30 and 120 min. Regarding seeds of high physiological quality, there was an increase in the germination velocity index of 1.1 to 1.2 times in ozonated seeds at 10 mg L⁻¹, compared to the non-ozonated seeds. According to the multivariate analysis, the inlet ozone concentration of 10 mg L⁻¹ associated with exposure times of 30 and 120 min showed similar results for seeds with low initial germination percentage. Based on the obtained results, we concluded that regardless the initial corn seeds quality, the recommended treatment is made by the combination of inlet ozone concentration of 10 mg L⁻¹ and exposure time of 30 min. Also, greater benefits are obtained from the application of ozone gas in corn seeds of low initial physiological quality. The ozonation proved to be a promising technique for seed treatment since it increased germination percentage and shoot and seedling lengths.