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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)). Sweetpotato roots often are damaged by a complex of insects, including the larvae of wireworms; cucumber beetles (Diabrotica balteata LeConte and D. undecimpuncta ta howardi Barber); Systena spp. (S. blanda Melsheimer, S. elongata Fabricius, S. frontalis Fabricius) (these three groups are known as the "WDS complex" because their damage is similar); sweetpotato flea beetle

The southern root-knot nematode, Meloidogyne incognita [(Kofoid & White) Chitwood], causes serious economic losses to melon (Cucumis melo L.) production in the United States. The present study was conducted to determine if separable differences in nematode resistance of Cucumis melo could be found at some inoculum level. Five C. melo lines were compared with Cucumis metuliferus Naud. (C701A), a highly resistant species, for root necrosis, galling, egg mass production, and reproduction when inoculated at 0, 500, 1000, 2000, or 5000 nematode eggs per plant. Using these criteria, melon line C880 inoculated with 1000 eggs per plant was highly susceptible, while PI140471, PI 183311, and the cultivars Chilton, Georgia 47, Gulf Coast, Planters Jumbo, and Southland were less susceptible. In greenhouse tests with an inoculum level of 1000 eggs per plant, low levels of resistance were evident. A thorough screening of the available germplasm against M. incognita may identify higher levels of root-knot nematode resistance for incorporation into improved melon cultivars.

The USDA has released a new cream-type southernpea [Vigna unguiculata (L.) Walp.] cultivar that is well adapted for productionthroughout the southern United States. The new cultivar, named `Tender Cream', is the product of a backcross breeding procedure to transfer the dominant Rk gene for root-knot nematode resistance from `Floricream' into `Carolina Cream'. `Tender Cream' is resistant to cowpea curculio, root-knot nematodes, southern bean mosaic virus, cercospora leaf spot, southern blight, rust, and powdery mildew. `Tender Cream' outyielded the cream control in the 1992, 1993, and 1994 Regional Southernpea Cooperative Trials by 5.4%, 11.0%, and 18.8%, respectively. It outyielded its root-knot-nematode-susceptible `Carolina Cream' isoline by 22.3% in a replicated 1994 test conducted in a field infested with a natural population of the southern root-knot nematode. Canned samples of fresh `Tender Cream' peas scored well during 3 years of testing at the Univ. of Arkansas.

A two year study was conducted to evaluate the efficacy of insect resistance in sweetpotato cultivars from our breeding program in combination with an insecticide (fonofos) and/or a parasitic nematode (Steinernema carpocapsae). In the laboratory, use of the parasitic nematode resulted in 99% mortality of Diabrotica larvae. In both years, much higher control of damage by all insect classes was achieved by the use of resistant cultivars in combination with a nematode and/or fonofos treatment. Analysis of the first year's field data showed the parasitic nematode treatment gave good damage protection against the WDS (Wireworm, Diabrotica, Systena), sweetpotato flea beetle, but not grubs. In this same year, fonofos only gave good protection against WDS. In the second test year, fonofos gave good protection against WDS, but the nematode did not. High moisture conditions may have affected the efficacy of the parasitic nematode. Host plant resistance by sweetpotato cultivars appears to be less affected by variable field conditions and accounted for 64% of the total crop protection (compared to the check susceptible line).

The test involved the use of a control (untreated), an entomopathogenic nematode (Steinernema carpocapsae), a granular insecticide (Dyfonate 2.24 Kg ai/ha) in combination with 7 sweetpotato cultivars having varying levels of resistance and susceptibility to soil insect damage. The parasite was applied three times at monthly intervals (67/cm2). The parasite or insecticide did not reduce root injury by soil insects as compared to the control (untreated). Wireworms, Diabrotica sp. and Systena sp. damage in the resistant cultivars Regal, Southern Delite, Excel and Resisto was less than for the susceptible cultivars (SC–1149-19, Jewel and Centennial). Sweetpotato flea beetle resistance was observed for all cultivars except SC–1149-19 which was susceptible. In this test resistant cultivars were more effective in reducing soil insect damage than the biological or chemical control methods.

Twenty-two sweet potato [Ipomoea batatas(L.) Lam.] clones with a wide range in metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] tolerance were used to establish narrow sense heritability estimates (h2) using a greenhouse procedure. The heritability estimates were obtained from simple linear regressions (h2= 2b) of injury rating, shoot fresh weight, and change in shoot fresh weight of offspring against the same responses of parents at metribuzin concentrations of 0, 0.3, and 0.6 ppm in the potting medium and averaged data for the two concentrations. These values ranged from 0.85 to 1.0, indicating that a recurrent mass selection process should be an appropriate approach to developing metribuzin-tolerant cultivars. Several highly tolerant clones were identified.

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.

Soil insect root injury to resistant sweet potato [Ipomoea batatas (L.) Lam.] cultivars ‘Regal’ and ‘Southern Delite’ was compared to injury to ‘Jewel’ and ‘Centennial’ in trials with the resistant-standard W-13 and the susceptible-standard SC 1149-19. Injury by three groups of insects was evaluated: the wirewoom-Diabrotica-Systena complex (WDS), which includes the southern potato wireworm (Conoderus falli Lane), the tobacco wireworm (C. vespertinus Fabricius), the banded cucumber beetle (Diabrotica balteata LeConte), the spotted cucumber beetle (D. undecimpunctata howardi Barber), the elongate flea beetle (Systena elongata Fabricius), the pale-striped flea beetle (S. blanda Melsheimer), and S. frontalis Fabricius (a flea beetle); the sweet potato flea beetle (Chaetocnema confinis Crotch.); and a white grub (Plectris aliena Chapin). Relative control estimates were obtained by comparison to the susceptible standard. ‘Regal’ and ‘Southern Delite’ provided good control of all three insect groups with control of all insect injuries of 79.2% and 81.0%, respectively. ‘Jewel’ and ‘Centennial’ were resistant to the sweet potato flea beetle and sustained less damage by WDS than the susceptible standard, but would still be classed as susceptible to WDS. ‘Centennial’ was as susceptible to the white grub as SC 1149-19. The levels of resistance demonstrated for ‘Regal’ and ‘Southern Delite’ would provide growers an alternative to insecticides for the control of these insects.