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), sweetpotato flea beetle ( Chaetocnema confinis ), elongate flea beetle ( Systena elongata ), wireworm larvae ( Conoderus sp.), white grub larvae ( Phyllophaga sp. and Plectris aliena ), sugarcane beetle ( Euetheola rugicepes ), and sweetpotato weevil

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the wireworm-cucumber beetle-flea beetle (WDS) severity index ( Chalfant et al., 1990 ). This complex of insect pests consists of several species of wireworms (e.g., Melanotus communis and Conoderus sp.), banded and spotted cucumber beetles

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recommendation, to control an exceptional outbreak of wireworm that had seriously damaged the potato crop in previous years. The association of OFO with γ-CHC was not definitive, however, because 5 of the 13 potato samples most severely affected by OFO were grown

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The reactions of eight sweetpotato [Ipomoea batatas (L.) Lam.] introductions were categorized for root damage by wireworms, Diabrotica sp., Systena sp. (WDS), sweetpotato flea beetle (SPFB), and grubs. Clones were compared with resistant (`Regal') and susceptible (`SC-1149-19') entries. The number of resistant clones for the WDS, SPFB, and grubs were three, four, and one, respectively, intermediate five, four, and one, and susceptible zero, zero, and six, respectively. This test demonstrated that significant levels of soil insect resistance exist in these sweetpotato introductions for use by plant breeders.

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Abstract

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.

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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)].

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Abstract

Advances attained by the sixth generation of mass selection in sweet potato (Ipomoea batatas (L.) Lam.) were assessed. The objective was to combine multiple resistances to pathogens, nematodes and insects with other desirable production and market qualities. Although progress from 6 single-year cycles of selection was encouraging, a change to 2-year cycles was indicated. Generation 6 contained high frequencies of flowering and seed set, attractive root shape, orange flesh, thin cortex, root specific gravities of about 1.02, acceptable yield, and resistance to fusarium wilt (Fusarium oxysporum f. sp. batatas (Wr.) Snyd. and Hans.), the southern root-knot nematode (Meloidogyne incognita (Kofoid and White) Chitwood) and the following soil insects: the southern potato wireworm (Conoderus falli Lane), the banded cucumber (Diabrotica balteata LeConte), the spotted cucumber beetle (D. undecimpuncta howardi Barber), the elongate flea beetle (Systena elongata (F.)), a white grub (Plectris aliena Chapin), and the sweet-potato flea beetle (Chaetocnema confinis Crotch).

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This study was designed to determine if the preference of soil insects for sweetpotato [Ipomoea batatas (L.) Lam.] cultivars is affected by the proximity of resistant or susceptible plant cultivars at various spacings. Comparisons were made for damage caused by wireworms (Conoderus spp.), Diabrotica spp., Systena spp., sweetpotato flea beetles (Chaetocnema confinis Crotch), and grubs (Plectris aliena Chapin; Phyllophaga ephilida Say) in previously reported resistant and susceptible cultivars. Field plots were planted with a resistant cultivar, a susceptible cultivar, or the two cultivars intermixed. Large roots exhibited more insect damage than medium and small roots. When plant spacing was increased, roots were larger and insect damage more severe. Mixed plantings of resistant and susceptible cultivars significantly reduced insect damage in the susceptible plants. Planting regime did not influence insect damage for the resistant cultivars.

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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.

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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). Wireworm, Diabrotica and Systena damage in the resistant cultivars Regal, Southern Delite, Excel and Resisto was less than for the susceptible cultvars (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.

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