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) but this resistance has not yet been incorporated into cultivars. Chemical control of downy mildew is necessary to achieve high yields in the absence of high host plant resistance. The discovery of systemic fungicides was a major advance over

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is known to damage more than 50 plant species, including corn, sorghum, cotton, rice, and bermudagrass ( Luginbill, 1928 ). Multiple overlapping generations of S. frugiperda occur within 1 year and infest several host species. Resistance to older

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development of fungicide resistance likely requires a multilayer system for the host to maintain Botrytis resistance. Vitis vinifera , the cultivated grape species grown for its high-quality berries, is highly susceptible to Botrytis . Resistance to

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-resistant ones. This strategy, known as host plant resistance, or HPR, is an important strategy in agricultural and forested settings ( Beck, 1965 ; Herms, 2002 ). With mounting social and regulatory pressures demanding the use of less pesticides in urban and

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. In conclusion, the combination of host resistance, effective fungicide sprays, and cultural practices (pathogen-free seed, crop rotation, weed control, plant spacing, and timed and limited irrigation) is key for the management of onion leaf and neck

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Heliothis zea (Boddle) is one of agriculture's worst insect pests. Reduction in crop productivity and costs for insecticidal control of this cosmopolitan pest cost U.S. agriculture many millions of dollars annually. The sesquiterpenes (+)-E-å-santalen-12-oic and (+)-E- endo- β–bergamoten-12-oic acids isolated from hexane leaf extracts of the wild tomato species, Lycopersicon hirsutum, have been shown to attract and stimulate oviposition by female H. zea. Extracts from other host plants (tobacco, corn, and cotton) also possess attractant/oviposition stimulant activity to female H. zea. Studies are underway to assess the potential use of these and other phytochemicals for the control or monitoring of population levels of H. zea in tomato, corn and cotton fields.

The isolation and structural identification of insect pest oviposition stimulants in horticultural crop species can provide valuable information to plant breeders involved in developing cultivars with improved insect host plant resistance. This information could be used to develop cultivars lacking the chemical cues used by insects for host plant location and recognition. Risks of public exposure to toxic insecticides through consumption of agricultural produce and polluted ground water emphasize the critical need for the development of crop genotypes with improved best plant resistance as a supplementary method of insect pest management in agricultural ecosystems.

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The Colorado potato beetle, Leptinotarsa decemlineata (Say), is the most serious insect pest of potatoes throughout the eastern and north central United States. Host plant resistance to the Colorado potato beetle has been identified in wild Solanum species and Bt-transgenic potato lines. Detached-leaf bioassays (72 h) were conducted on insecticide-resistant, first instar Colorado potato beetles to study the effectiveness of individual and combined host plant resistance traits in potato. Potato lines tested include non-transgenic cultivars (`Russet Burbank', `Lemhi Russet', and `Spunta'), a line with glandular trichomes (NYL235-4), a line with high foliar leptines (USDA8380-1), and transgenic lines expressing either codon-modified Bt-cry3A or Bt-cry5 (Bt-cry1Ia1). Bt-cry3A transgenic lines, foliar leptine line, and foliar leptine lines with Bt-cry5 had reduced feeding compared to non-transgenic cultivars. Glandular trichome lines and glandular trichome lines with Bt-cry5 did not reduce feeding in this no-choice feeding study. Some Bt-cry5 transgenic lines, using either the constitutive promoters CaMV35s or (ocs)3mas (Gelvin super promoter), were moderately effective in reducing larval feeding. Feeding on Bt-cry5 transgenic lines with the tuber-specific patatin promoter was not significantly different than or greater than feeding on the susceptible cultivars. Mortality of first instars was highest when fed on the Bt-cry3A lines (68% to 70%) and intermediate (38%) on the Bt-cry5 `Spunta' line SPG3 where the gus reporter gene was not included in the gene construct. Host plant resistance from foliar leptines is a candidate mechanism to pyramid with either Bt-cry3A or Bt-cry5 expression in potato foliage against Colorado potato beetle. Without multiple sources of host plant resistance, long-term sustainability is questionable for a highly adaptable insect like the Colorado potato beetle.

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Feeding intensity of adult Japanese beetle (Popillia japonica Newm.) was compared among 27 taxa of Prunus host plants during 24-hour no-choice feeding trials conducted on individual leaves. Fecal dry mass per beetle, a measure of feeding intensity, varied from 0 mg·d-1 for Prunus padus L. to 20.4 mg·d-1 for P. sargentii Rehd. and P. tomentosa Thunb. Prunus padus, P. laurocerasus L., P. mahaleb L., P. serotina Ehrh., P. virginiana L., P. americana Marsh., P. ×yedoensis Matsum., and P. besseyi Bailey were resistant based on feeding intensities of <4.3 mg·d-1 (levels not significantly different from zero). Feeding intensity decreased exponentially as endogenous foliar cyanide potential increased. Evaluation of the cyanogenic glucoside prunasin in artificial diets showed a similar relationship with feeding being reduced by 50% (ED50) at 4.9 mmol·kg-1 in the diet. Prunus mahaleb was highly resistant to Japanese beetles despite having low cyanide potential. Two coumarin compounds known to exist in P. mahaleb, herniarin and coumarin, were tested in artificial diets and were effective feeding deterrents with ED50 values of 5.9 and 2.5 mmol·kg-1 in the diet, respectively. This research demonstrated a wide range of host plant resistance to feeding by adult Japanese beetles and further indicates that prunasin, herniarin, and coumarin are important factors in host plant resistance to this pest.

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Host plant resistance is a key element in a viable integrated pest management plan. Resistance to plant feeding was observed on Valmaine cos lettuce, Lactuca sativa L. to the banded cucumber beetle (BCB), Diabotica balteata (LeConte). In no-choice feeding evaluations, adult BCB contained on three week old Valmaine plants gained less weight, died and fed less than individuals contained on susceptible Tall Guzmaine cos lettuce. Individual female BCB held on Valmaine plants also did not have egg development as in those individual held on Tall Guzmaine. Based on weight gain and feeding damage F1, F2, and F3 segregation data indicates that the resistance factor is recessive in inheritance and controlled by more that one gene.

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Abstract

Populations of cabbage looper, Trichoplusia ni (Hubner), and the imported cabbageworm, Pieris rapae (L), generally were about the same on 4 cabbage cultivars treated weekly with a spray mixture containing Bacillus thuringiensis Berliner (45 g/ha) and chlordimeform (1400 g/ha). However, ‘Stein’s Early Flat Dutch’ and ‘Ferrys Round Dutch’ had more plants with uninjured heads and wrapper leaves than did ‘Copenhagen Market No. 86’ and ‘Resistant Golden Acre’. Data suggest complementary effects of host plant natural resistance and the microbial-chemical spray. ‘Stein’s Early Flat Dutch’ was most resistant and ‘Resistant Golden Acre’ was most susceptible, on the basis of the amount of feeding injury.

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