Control of Volunteer Corn and Giant Foxtail in Soybeans

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Abstract
In field studies, HOE 22870 [4-(4′-chlorophenoxy)-phenoxy-α-propionic-isobutylester] and HOE 23408 methyl 2-[4-(2,4-dichlorophenoxy)phenoxy] propanoate at 0.84 to 3.36 kg/ha were sprayed over the top of soybeans [Glycine max (L.) Merr.], corn (Zea mays L.), and giant foxtail (Setaria faberi Herrm.). Rates of 0.84 or 1.68 kg/ha of either herbicide controlled corn and giant foxtail. Soybeans tolerated 3.36 kg/ha (the highest rate used) of either herbicide. Both herbicides performed quite similarly, but HOE 22870 was generally more effective on giant foxtail and less effective on corn than was HOE 23408. The optimum time of application, in terms of soybean development, was the first trifoliolate stage. At this stage, corn had four to five leaves and giant foxtail had three to five leaves. HOE 23408 was applied to 32 inbred lines of corn in a greenhouse study. Several inbreds had considerable tolerance. When HOE 23408 at 0.56 kg/ha was applied to these 32 inbreds in a field study, control ranged from 100% for the most susceptible inbred to 22% for the most resistant inbred. At 1.12 kg/ha, control of corn ranged from 100% to 42%.