No abstract

The sweet potato [Ipomoea batatas(L.) Lam.] cultivars ‘Jewel’, ‘Centennial’, ‘Caromex’, and breeding lines ‘W-70’, ‘W-152’, and ‘Tinian’ (PI 153655) were evaluated for metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as–triazin5(4H)-one] tolerance in greenhouse and field studies. Tinian was the most tolerant line. Its yields were not reduced by 2.2 kg/ha metribuzin in the field. Jewel, Centennial and W-152 were intermediate in response to metribuzin, and W-70 and Caromex were most susceptible. Regression analyses indicated a high correlation between the response of sweet potato cultivars to 0.5 ppm metribuzin incorporated in a potting mix in the greenhouse and their response to 1.1 kg/ha metribuzin applied after transplanting in the field.

No abstract

This 2-year study was conducted to determine if soil insect damage could be reduced in sweetpotato [Ipomoea batatas (L.) Lam] by treatment with an insecticide (fonofos) and/or a parasitic nematode (Steinernema carpocapsae Weiser), in conjunction with sweetpotato cultivars that differed in susceptibility to soil insect damage. Analysis of field data for the first year showed that the parasitic nematode provided significant damage protection of sweetpotato from wireworms (Conoderus spp.), Diabrotica sp., Systena sp., and sweetpotato flea beetle (Chaetocnema confinis Crotch), but not from grubs (Plectris aliena Chapin; Phyllophaga ephilida Say). In this same test, fonofos used alone provided protection against wireworm-Diabrotica-Systena (WDS complex) damage. In the second test, the nematode did not provide soil insect protection for the WDS complex, but fonofos did reduce damage for these insects. Poor efficacy in the second test with the nematode probably was due to high rainfall, which saturated the soil. Resistant cultivars provided good protection for all three categories of damage. When used with the insect-susceptible check `SC 1149-19', the nematode or fonofos treatments provided better control for all insect categories in the first test. In both years, much higher control of damage by all insect classes was achieved by the use of resistant cultivars in combination with the nematode and/or fonofos treatment (64% higher crop protection than the susceptible check line). Chemical name used: O-ethyl-S-phenylethylphosphonodithioate [fonofos (Dyfonate 10G)].