Combination of diatomaceous earth, deltamethrin, and artificial coolingfor insect management in paddy rice in subtropical climate


Abstract: Paddy rice in southern Brazil is usually stored in metallic silos waiting to be milled forstorage periods as long as 16 months. The longer the storage period the higher is the pressure ofinsects. The main problem has been large infestation of coleopterans on the top layer of the grainmass due to the head space effect – high temperatures and fines. The objective of this study is toprovide the rice industry with a program for insect management in large scale facility using acombination of physical and chemical methods to safely protect the paddy rice against insects forat least one year. In this program 40 silos with capacity for 3500 tons/silo of paddy rice weretreated as follows. Two portions of about 60 tons of rice were treated with a combination of300ppm of diatomaceous earth (DE) (commercial name KEEPDRY) plus 30ppm of powderdeltamethrin (K-obiol 2 P a.i. 2%) per ton of rice. The treatment was applied as the grain wastransported to the silo by a system of bucked elevator, screw, and conveyor belt. After the bottomportion was filled into the silo it was levelled and the silo filled with untreated grain. The toplayer was filled with the other portion of 60 tons treated rice, and levelled. After the silo wascompletely filled, cold air produced artificially was insufflated throughout the aeration system at0.12m3/min/t to bring the temperature of the grain mass down to 12-14°C. Temperaturemonitoring of the grain mass was made with thermocouples installed in each silo. As thetemperature increased, new cycles of chilled aeration or natural cold air from the cold fronts wereused to keep the grain temperature at a safe range to avoid insect infestation. The combination ofDE with pyrethroid plus chilled aeration is a novel approach to manage paddy rice for long termstorage, reducing food and environmental contamination, personal exposure at competitive cost.

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