Insecticide-oil droplet size effect on fall armyworm larvae control via chemigation
1993
Koo, Y.M. | Chandler, L.D. | Sumner, H.R.
A mixture of an insecticide (chlorpyrifos) and immiscible oil was applied through a laboratory-simulated irrigation system onto corn and cotton plants that contained fall armyworm larvae (FAW), Spodoptera frugiperda (J.E. Smith). Effects of insecticide-oil (I/O) droplet size, active chemical rate, and crop canopy architecture on percent larval control were evaluated. Small I/O droplets (D(V.5) = 6 micrometers) were less effective in controlling FAW larvae than were large droplets (D(V.5) = 74 micrometers). The percent larval control reached 90.4% and 83.6% on corn and cotton, respectively, at half the low recommended dose. The result confirmed that chemigation was effective on insect control. Percent larval control was higher on corn plants than on cotton plants because of an architectural advantage of the corn canopy which directed insecticide to the larval feeding location. The influence of I/O droplet size on larval control was more apparent on cotton at the lower chemical rate than on corn at the higher chemical rate. Applying optimal I/O droplet sizes in chemigation significantly reduced the use of insecticide needed to achieve improved efficacy.
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