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- Author or Editor: James M. Schalk x
A replicated greenhouse study was conducted to confirm the availability of resistance to western Rower thrips in pepper germplasm. Host-plant resistance ratings confirmed earlier observations that there is a considerable amount of variability within pepper germplasm for reaction to F. occidentalis. Plants of `Keystone Resistant Giant', `Yolo Wonder L', `Mississippi Nemaheart', `Sweet Banana', and `California Wonder' were resistant to the insect and exhibited only mild symptoms of damage. Plants of `Carolina Cayenne', `Santaka', and `Bohemian Chili', however, exhibited the symptoms of severe thrips damage, i.e., poorly expanded, deformed, and distorted leaves; greatly shortened internodes; and severe chlorosis. The resistance to F. occidentalis in pepper appears to be due to tolerance mechanisms, not antixenosis (nonpreference) or antibiosis mechanisms. Thrips-resistant cultivars could be used as a cornerstone in an integrated pest management program for greenhouse pepper production.
A series of outdoor screen-cage tests were carried out over a 4-year period to determine the range of available resistance in cowpea [Vigna unguiculata (L.) Walp.] to the southern green stink bug (SGSB) [Nezara viridula (L.)]. A total of 124 cowpea cultivars, breeding lines, and plant introductions (PI) were evaluated in an unreplicated test in 1981 (Test I); and PI 293476, PI 293557, PI 293570, PI 353074, and PI 354580 were identified as having potentially useful levels of resistance. In a subsequent replicated test in 1982 (Test II), these introductions exhibited less SGSB seed damage and significantly greater seed yield than did the susceptible check Ala 562-3-1-2. PI 293557 and PI 293570 were evaluated further in replicated tests in 1983 (Test III) and 1984 (Test IV) using both infested and uninfested treatments. Both accessions produced appreciable seed yields under conditions that significantly reduced yields in the susceptible checks. Tolerance to SGSB injury appears to be responsible for the resistance exhibited by PI 293557 and PI 293570.
First generation of larvae of the Colorado potato beetle (Leptinotarsa decemlineata (Say)) were primarily responsible for a 67% reduction in yield of tomato (Lycopersicon ‘esculentum Mill.) when their numbers increased from 5 to 10 per plant.
Leaf disks of tomato, Lycopersicon esculentum Mill, and L. hirsutum C. H. Mull, subjected to feeding by the Colorado potato beetle, Leptinotarsa decemlineata (Say), were altered by insect age, sex, moisture level, and plant age. Feeding response was altered by temperatures of 21.1°C or 26.7° in young adult beetles, but not in larvae or older adults. Resistance to feeding by the insect was found with L. hirsutum lines PI 134417 and PI 134418.
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.
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.
‘Excel’ sweet potato [Ipomoea batatas (L.) Lam.] was developed jointly by the USDA and the South Carolina Agricultural Experiment Station. This cultivar has high yield and excellent baking flavor, in combination with high levels of resistance to a wide array of disease and insect pests. Additionally, it has promise for use in snack foods.