The silverleaf whitefly (Bemisia argentifolii Bellows & Perring) is an important pest of tomatoes in Florida and elsewhere. Associated with populations of the whitefly is an irregular ripening disorder of fruit characterized by inhibited or incomplete ripening of longitudinal sections of fruit and by an increase in the amount of interior white tissue. Experiments were conducted during the spring and fall tomato production seasons of 1995 and 1996 to elucidate the relationship of nymphal and pupal density with severity of the disorder. Insecticides or insecticide combinations were applied at predetermined densities of whitefly nymphs and pupae and the subsequent severity of the disorder was rated separately for external and internal symptoms on red ripe fruit harvested weekly. Expression of irregular ripening symptoms, especially external symptoms, were correlated positively to the density of whitefly nymphs and pupae (number·10-1 terminal leaflets on the seventh to eighth leaf from the top of a main or lateral stem) increased. Expression of external symptoms tended to be better correlated with whitefly density when symptom severity was rated 1 and 3 weeks after estimating whitefly density for the spring and fall seasons, respectively. Expression of internal symptoms tended to be more consistently correlated with whitefly density when symptom severity was rated 2 and 3 weeks after estimating whitefly density for the spring and fall seasons, respectively.
Curtis H. Petzoldt, Stephen Reiners, and Michael P. Hoffmann
The document Cornell Integrated Crop and Pest Management Guidelines for Commercial Vegetable Production was revised in 1999 to become inclusive and integrative of all aspects of crop and pest management. As an adjunct to the printed publication, additional information was presented in tables at an Internet web site. Links on the web site were made to other sites with more detailed information on specific topics, such as photographs of pests and diagnostic information, soil fertility testing, cover crops, environmental impact of pesticides, pesticide labels, and images, sources, and life cycles of beneficial insects. The revision and web site have proven to be popular with cooperative extension staff and the vegetable industry in New York.
Rosalind Cook, Anne Carter, Pamela Westgate, and Ruth Hazzard
Corn oil and Bacillus thuringiensis ssp. kurstaki (Bt) applied directly into the silk channel of a corn ear has been shown to be an effective pesticide against corn earworm, Helicoverpa zea (CEW), and european corn borer, Ostrinia nubilalis (ECB). Field studies were conducted in 2000 and 2001 to determine the influence of application timing on ear quality at harvest. Two blocks of corn were planted during each year to observe treatment effects under varying populations of the two insect species. The treatment consisted of 0.5 mL (0.017 floz) of food grade corn oil containing a suspension of Bt at 0.08 g (0.003 oz) a.i. per ear applied directly into the silk channel at the husk opening. One treatment application was made on each silk day 3 through 11 from first silk; silk day 1 was the first day that 50% or more of ears had 2.5 cm (1 inch) of silk protruding from the husk. One treatment did not receive the oil + Bt suspension. All ears were harvested at milk stage, on silk day 25. The number of CEW larvae in treated ears increased with later application days in 2000, but not in 2001. Damage from larval feeding was mainly found near the tip of the ear, and damage ratings were lower compared to untreated ears for all treatment days for both plantings in 2000, and through application day 8 in the late planting of 2001. ECB larvae were reduced for all treatment days in both plantings in 2000 and the late planting of 2001. The percentage of ears rated as marketable (i.e., free of feeding damage) ranged from 71% to 100% in treated plots compared to 30% to 77% in the untreated plots. There was a linear decrease in marketability with later application days in two of the four plantings. The greatest decrease in marketability was after application day 7. Because the oil application affects kernel development at the tip, the length of ear with under-developed kernels, or cone tip, was measured. The number of ears with cone tip decreased linearly with the later application days in all plantings. There was 10% conetip or less after day 7 in 2000 and day 6 in 2001. The best combination of effective insect control resulting in the highest rates of marketable ears with the least degree of cone tip was achieved in this experiment by application of oil + Bt suspension on day 7. Year to year variation in the environment would suggest a range from day 6 to 8.
Michael A. Norman, Kim D. Patten, and Sarangamat Gurusiddaiah
Three indicator species [rye (Secale cereale L.), radish (Raphanus sativus L.), and alfalfa (Medicago sativa L.)] and nonrooted cuttings of `Stevens' cranberry (Vaccinium macrocarpon Ait.) vines were grown in pots to establish the dose response levels for a sand-applied phytotoxin(s) from a crude extract of Pseudomonas syringae (strain 3366) culture. At 114 ppm [milligrams phytotoxin(s)/kilograms sand], the material was noninhibitory, whereas 1140 ppm reduced root and shoot growth significantly in all four species. In subsequent experiments, a 10-ppm dose controlled corn spurry (Spergula arvensis L.) and fireweed (Epilobium angustifolium L.) seedlings, while 103 ppm reduced root or shoot growth of cuttings of the perennial weeds birdsfoot trefoil (Lotus corniculatus L.) and silverleaf (Potentilla pacifica Howell). Root and shoot growth of partially rooted `McFarlin' cranberry vines was reduced at 103 and 563 ppm, respectively. The phytotoxin(s) could potentially control germinating annual weeds in newly established `Stevens' cranberry bogs.
John W. Kelly, Peter H. Adler, Dennis R. Decoteau, and Sarah Lawrence
The greenhouse whitefly [Trialeurodes vaporariorum (Westwood)] is a major pest of many greenhouse crops, including poinsettias (Euphorbia pulcherrima Wild.). Chemical control of the greenhouse whitefly is difficult; therefore, alternative controls are needed.
J. E. Epperson, C. C. Dowler, R. B. Chalfant, A. W. Johnson, N. C. Glaze, and D. R. Sumner
This study was designed to determine the effect of pest control intensity on net returns in multiple cropping systems. The study is tempered with an evaluation of risk. The cropping system encompasses: turnip greens (Brassica rapa L.) for processing, field corn (Zea mays L.), and southern peas [Vigna unguiculata (L.) Walp. ssp. unguiculata] for processing. Within the ranges of pest control intensities studied, less intensive control resulted in higher net returns. Further, the level of greatest pest control intensity consistently yielded negative net returns. This level, however, was less risky in terms of gross returns. Risk did not differ significantly between the other levels of pest control.
R.A. Dolbeer, P.P. Woronecki, and J.R. Mason
Each of 11 cultivars of sweet corn (Zea mays L.) was presented to red-winged blackbirds (Agelaius phoeniceus L.) in an aviary under no-choice conditions in 1985. This evaluation was repeated in 1986 with eight cultivars, five of which had been tested in 1985. In both years, there were significant differences in damage among cultivars; the damage rankings of the cultivars tested in both years were correlated. Total husk weight and husk weight beyond the cob tip individually explained 68% to 69% of the variation in damage among cultivars. Husk characteristics were more important than kernel characteristics in determining the amount of damage a cultivar received. Six of the cultivars evaluated in a field test near a blackbird roost showed differences in damage similar to that found in the aviary. In the field test, the most- and least-resistant cultivars had 16% and 76% of the ears damaged, respectively. Resistance is a viable approach to reduce damage in situations where sweet corn is grown near concentrations of blackbirds.
James E. Faust, Elizabeth Will, and Millie Williams
Graduate students received training in total crop management (TCM) techniques including pest scouting and trapping, nutritional monitoring, and graphical tracking of crop height. In 1995, one student visited five greenhouse businesses biweekly during the poinsettia (Euphorbia pulcherrima Willd.) season to provide TCM training to one greenhouse employee per business. In 1996, a second student visited one greenhouse business every week during the poinsettia crop to conduct the TCM program for that business. The students benefited from the gained practical knowledge of greenhouse production techniques and TCM techniques, and they also benefited from the opportunity to visit commercial greenhouses and interact with staff throughout the production cycle for an entire crop. This program also provided the students with the opportunity to develop their teaching, communication and training skills. The participating growers benefited during this study from receiving useful production information and TCM training. An evaluation of the program conducted in 1998 indicated that four of the five participating businesses continue to use some TCM techniques, while two of the five have fully integrated the TCM program into their normal production routines.
Andrea B. da Rocha and Ray Hammerschmidt
A major challenge facing horticultural crop production is the need to provide field and postharvest disease control measures that help maintain high quality plant products. Producers and consumers also expect high quality produce with minimal or no pesticide residues and competitive prices. The chemical management of disease is further complicated by the development of fungicide resistance in many important pathogens. Because of these concerns, an alternative or complementary approach is the use of disease resistance inducers that activate the natural defenses of the plant. Induced disease resistance in plants has been studied in many different pathosystems for nearly a century. Resistance to plant disease can be induced systemically by prior infection with pathogens, by certain non-pathogenic microbes that colonize the surface of roots and leaves, or by chemicals. The application of resistance inducers should protect plants through the induction of defenses that are effective against a broad spectrum of pathogens. Over the last few years, a number of materials that could potentially be used as inducers of resistance in horticultural crops have been identified. Some of these materials are already commercially available. Although induced resistance is known to provide a broad spectrum of disease suppression, it may not be a complete solution because variation in the efficacy of disease resistance induction has been observed. The variation in the response may be dependent on the plant species and even cultivars, as well as variability in the spectrum of pathogens that resistance can be induced against. Induction of resistance depends on the activation of biochemical processes that are triggered in the plant, and therefore a lag time between treatment and expression of resistance occurs. This lag effect may limit the practical application of disease resistance inducers. Since the efficacy of the inducers also depends on the part of the plant that was treated, the product delivery (i.e., how the inducers would be applied in order to optimize their action) is another factor to be considered. Some studies have shown that there may be side effects on growth or yield characteristics when certain inducers are used. Understanding the biochemical interactions occurring between plants, pathogens and the inducers will provide information that may be useful for the optimization of this new approach on disease control. Approaches to integrate induced resistance with other management practices need to be investigated as a means to aid the development of sustainable disease management programs that are effective as well as economically and environmentally sound.
Rachel Leisso, Bridgid Jarrett, Katrina Mendrey, and Zachariah Miller
Codling moth (Cydia pomonella) is a major insect pest of apple (Malus domestica). If unmanaged, then codling moth can infest nearly all apples in an orchard, where the flesh-tunneling larva leave frass-laden tracks in the fruit. Insecticide-based management requires accurate application timing (typically based on adult moth and/or degree-day monitoring) and multiple spray applications. Both the season-long commitment to codling moth monitoring and management and limited familiarity with insecticides, application tools, and proper application procedures can prevent a small-scale or backyard grower from effectively limiting fruit damage. In addition, an increasing segment of growers is interested in nonchemical alternatives. Bagging fruitlets early in the season could be a simple and effective method of codling moth management for this subset of growers. At our research orchard in Corvallis, MT, we tested a method combining fruit thinning and bagging using plastic bags the first season and nylon bags the second season. Plastic bags reduced the incidence of codling moth damage to fruit from 34% to 10%, but european earwig (Forficula auricularia) frass, which was found in more than 50% of plastic-bagged apples, made harvesting the fruit unappealing. We tested nylon fruit bags during the second year of the study. These bags did not significantly reduce the incidence of codling moth. Both the soluble solids content and titratable acidity were higher in unbagged fruit during the second year of the study, whereas color measurements indicated bagged fruit were greener on the shaded side of the fruit. Failure of the nylon bags may have been attributable to eggs laid before bagging, eggs laid or larva burrowing through bagging, or improper bag application methods. Further research could assess whole-tree bags, the addition of rubber bands or twist ties when applying nylon bags, pretreatment of fruit with horticulture oil, and/or dipping nylon bags in kaolin clay before application; however, these steps add time and increase costs, which may discourage the small-scale fruit grower. Overall, results indicate that fruit bagging holds promise for codling moth management; however, further work is needed to optimize the methodology.