Aeration Alone Versus Chlorpyrifos-Methyl Treatment Followed by Aeration for Wheat Stored in Georgia: Simulated Field Test

Abstract

Wheat treated on 7 July with 6 ppm chlorpyrifos-methyl was artificially infested with lesser grain borer, Rhyzopertha dominica (F.), and rice weevil, Sitophilus oryzae (L.), and subsequently aerated when temperatures cooled, was compared with untreated wheat infested and aerated at the same conditions. Temperatures were monitored from 7 July to 5 April inside the bins and populations of the introduced species and a natural infestation of red flour beetle, Tribolium castaneum (Herbst), were assessed using probe traps and a grain trier. Average daily temperatures at 7 sample positions in untreated wheat were from 17.01 ± 0.53 to 21.46 ± 0.52°C, and were not significantly different from average temperatures at corresponding positions in treated wheat, which were from 16.00 ± 0.63 to 18.98 ± 0.60°C. Initial chlorpyrifos-methyl residue on treated wheat was 5.75 ± 0.51 ppm, but after 6 wk residues declined by 67.2-52.7%. Lesser grain borers collected from probe traps and trier samples were significantly more numerous in untreated wheat than in treated wheat on the 1st sample date (20 August) ; however, populations were larger in treated wheat on 2 later sample dates (12 November and 29 March). Few rice weevils or red flour beetles were collected from treated wheat. There was significantly more dockage (ground flour and insect frass) in untreated wheat than in treated wheat on 4 of 6 sample dates, while the percentage of insect-damaged kernels was significantly greater in untreated wheat than in treated wheat on all sample dates.