Integrated weed management strategies maintain sub-threshold levels of weeds. The remaining weeds may impact the feeding and habitation patterns of both potato leafhoppers and bean leaf beetles in a snap bean agroecosystem. The objective of our study was to determine the effect of interference between snap beans (Phaseolus vulgaris L.) and either redroot pigweed (Amaranthus retroflexus L.) or large crabgrass (Digitaria sanguinalis L.) on populations of potato leafhopper [Empoasca fabae (Harris)] and bean leaf beetle [Cerotoma trifurcata (Forster)]. Plots were seeded with redroot pigweed or large crabgrass at either the same time as snap bean planting (early) or when snap bean had one trifoliate leaf open (late). The weed density averaged two plants per meter of row. Bean leaf beetle populations, snap bean pod damage, and leaf defoliation were lower in weed-free plots compared to those with either early emerging pigweed or crabgrass. Leafhopper nymphs and adults were 31% to 34% less in plots with crabgrass emerging with snap beans compared to those in weed-free snap bean plots. Thus, the effect of sub-threshold densities of pigweed and crabgrass on insect pests in snap bean varied depending on the species and should be considered when deciding to integrate weed management approaches.
Joseph N. Aguyoh, John B. Masiunas and Catherine Eastman
Warren Roberts, Jonathan Edelson, Benny Bruton, Jim Shrefler and Merritt Taylor
Plots were established at the Lane Agricultural Center in Lane, Okla., in 2003 for the purpose of conducting research in certified organic vegetable production. A field was selected that had been in pine timber since 1985. The field was cleared, plowed, disked, and land-planed. To establish a baseline for future reference, soil samples were collected on a 30 × 30 ft grid. Lime was added to adjust the pH. Poultry litter was added to the field as a fertilizer, and was incorporated by disking. Turnips were grown as a cover crop during the winter of 2003–04. In Spring 2004, the field was divided into four equal sections, which were planted with either tomatoes, sweet corn, watermelons, or southern peas. Tomatoes were planted using both determinate and indeterminate types. Plants were selected based on reported properties of interest to organic growers, such as disease resistance, pest resistance, or heat-set capabilities. The cultivars with greatest yield were Sunny, Solar Set, Classica, Sun Leaper, and Mountain Fresh. Visual disease ratings were taken throughout the season. Copper sulfate was used as a fungicide. The cultivars with the lowest disease ratings were Amelia, Peron, Celebrity, Florida 91, and Mountain Fresh. The major insect pest throughout the season was aphids. Aphid counts reached 6.9 aphids per leaf on 11 June. Two applications of AzaDirect, a neem extract, reduced aphid populations to 1.0 aphid per leaf on 17 June, 0.1 aphid per leaf on 25 June, and 0 aphids on 9 July.
Curt R. Rom, Jason McAfee and Donn Johnson
Apple cultivar development is an important program necessary to sustain the existing fruit industry and stimulate new production systems for Arkansas and the region. The cultivar development program has two parts. First, currently available cultivars are tested with multiple trees for multiple years. Second, about 150 advanced selections from the Arkansas apple breeding program are evaluated in trials with multiple trees (2nd test) and in replicated trials (3rd test). The goal of both programs is to identify cultivars that have potential in the local production systems and for Arkansas' markets, and to identify those cultivars which are not adapted to the region. All cultivars and advanced selections are evaluated for ∂35 qualitative and quantitative characteristics, including time of bloom, time of harvest, length of harvest season, fruit aesthetic and internal quality, environmental adaptability especially to heat and high light, and insect and disease susceptibility. Primary diseases for which cultivars and selections are screened include fireblight, cedar apple rust, powdery mildew, black rot, white rot and bitter rot. Primary insect pests include mites, codling moth, plum curculio and Japanese beetle. Cultivars are evaluated in the field, under standard management conditions for five to seven years of production before summary evaluation. The program has identified cultivars including traditional cultivars, new cultivars, and heritage cultivars adaptable to the local and regional climates and suitable for those markets.
D. Michael Jackson and Janice R. Bohac
Production of sweetpotatoes is severely limited by several insect pests, and new pest management approaches for this crop are needed. A host plant resistance research program typically depends on reliable bioassay procedures to streamline evaluation of germplasm. Thus, bioassay procedures were developed for both adults and larvae of two cucumber beetle species (Diabrotica balteata and D. undecimpunctata). For the adult bioassay, a piece of sweetpotato peel (periderm & cortex with stele removed) was embedded periderm-side up in plaster in a Petri dish, and a single adult was placed on it. Plugs were changed as needed and adult longevity was measured. A laboratory bioassay also was developed for Diabrotica larvae. Plugs (0.9 cm diameter) of sweetpotato peel or stele were placed periderm-side up into sterile microcentrifuge tubes (1.5 mL) containing 0.5 mL water-agar to prevent desiccation. One second instar Diabrotica was added to each micro centrifuge tube, which was held at 25 °C for 12 days. Surviving larvae were weighed. Diabrotica larvae grew larger when they were fed stele than when they were fed peels of any sweetpotato genotype. Larval growth was not different among genotypes for any of the stele treatments. However, larval growth on the peel of the resistant genotypes (Regal and W-375) was significantly lower than for the susceptible cultivars Beauregard or SC1149-19. These bioassays were consistent with field results, indicating that these techniques could be useful for evaluating pest resistance in sweetpotato genotypes for Diabrotica and other insect species.
Richard P. Buchner
California walnut farmers compete with pests and diseases to produce an economically viable crop. Current control strategies work reasonably well for most pest and diseases. However, the future of these techniques is a matter of speculation. This presentation describes current production practices and potential alternatives to “traditional” pest and disease control. Codling moth, walnut husk fly, mites, navel orangeworm, aphids, and scale are typical insect pests that have an impact on California walnut production. Spray decisions using Integrated Pest Management, beneficial insect releases, mating disruption, insect growth regulators, and orchard sanitation offer potential alternatives. Major diseases include: Phytophthora crown and root rot, crown gall, oak root fungus, and walnut blight. Control options include careful site selection and orchard management, resistant rootstocks, competitive bacteria for crown gall control, and copper compounds for walnut blight suppression. Weed growth is related to the amount of light reaching the orchard floor. Mature trees often shade the orchard floor, subsequently reducing the need for weed suppression. Herbicides are typically used for vegetation control. Choice of irrigation system, cultivation, mowing, cover crops, and flaming offer potential alternatives either alone or in combination with conventional herbicides.
Pistachios are the single most-successful plant introduction to the United States in the 20th century. Part of this success is due to the alternative production practices that have made this crop more economical to grow. Controlled deficit irrigation (CDI) can produce 25% savings in irrigation water with no adverse effects. Reclaimed drainage water can be used for in-season irrigation up to 6 dS/m. Nitrogen applications can be adjusted for crop load and alternate bearing. Foliar sprays of boron, copper, and zinc can replace heavy ground applications to alleviated these micronutrient deficiencies. Some early season insect damage can be tolerated due to the tree's ability to compensate for the damage by filling a higher percentage of the remaining nuts, Maintaining a clean orchard floor can limit some insect pests. Mechanical pruning has been demonstrated to be cheaper and cause no loss in yield. Foliar fungal diseases can be partially controlled by limiting trajectory angle, frequency, and duration of irrigation or by using buried drip irrigation systems. Soil-borne fungal diseases and nematode damage are controlled by using resistant rootstocks.
Oregon's Willamette Valley is home to 99% of the U.S. domestic production of hazelnuts, Corylus avellana. There are currently around 30,000 acres of hazelnuts in Oregon. Hazelnuts are a relatively low resource input crop when compared to other orchard crops. They require few pesticide applications, and are harvested mechanically. Oregon State Univ. (OSU) developed an Integrated Pest Management (IPM) program for hazelnuts in the middle 1980s that is widely adopted in the industry today. Sampling schemes and action thresholds have been developed for the filbertworm (the most important insect pest), as well as: obliquebanded leafroller, filbert leafroller, and filbert aphids. In an example of classical biological control, a filbert aphid parasite, Trioxysis pallidus, was imported from Europe in 1984. Trioxysis has successfully established itself throughout the industry. As a result, the need for aphid control sprays has been significantly reduced. Current research in hazelnut IPM is focused on a “soft pesticide” program that features an insect growth regulator for filbertworm control. Recent research with isotopically labeled nitrogen seeks to improve the efficiency of nitrogen fertilization in the industry. The northern portion of the industry is affected by Eastern Filbert Blight. OSU research has secured registrations of effective fungicides and refined the control program for the blight. Work is being completed on a predictive model to quantify the extent of spore dispersal, based on accumulated rainfall.
Steven E. Newman, Michael J. Roll and Ronald J. Harkrader
There are many naturally occurring substances that have the potential to be adapted to modern pest control chemistry. Azadirachtin, an insect growth regulator, is one such naturally occurring compound that has been widely accepted in insect pest management. Quartenary benzophenanthridine alkaloids (QBAs) are known to be effective in the control of crop damaging fungal diseases. QBAs can be isolated from plants in the Papaveraceae. Extracts of Macleaya cordata, a species rich in QBAs, were formulated at 150 mg·L–1 QBA for spray application to greenhouse roses infected with Sphaerotheca pannosa var. rosae (powdery mildew). The QBA formulation was applied at 10-day intervals. Copper sulfate pentahydrate (Phyton27), piperalin (Pipron), and fenarimol (Rubigan) were also applied to mildew infected plants within the same greenhouse at their respective label rates for comparison. One day after treatment, the mildew infection was reduced 50% by QBA, whereas fenarimol, copper sulfate pentahydrate, and piperalin reduced the infection 50%, 75%, and 80%, respectively. Nine days after application, the mildew infection of QBA treated plants was less than 5% of the leaflet surface area. QBAs have the potential to be developed as a biorational fungicide for greenhouse use with both fungicidal and fungistatic activity.
A. Lopez-Carvajal, L. Grijalva-Contreras, J. Valenzuela-Ruiz, R. Juarez-Gonsalez and F. Robles-Contreras
Caborca, Sonora, is the principal raisin producer area in Mexico. It is estimated that over one-third of the fresh grape production is destined for raisins. There are no studies related to the insects that attack raisins in the fields during drying or in the processing plants where the raisins are stored for several months. The purpose of this study was to identify the insect pests and quantify the extent of the damage. Raisin samples were taken from the fields during drying and from the processing plants. The most abundant and frequent species identified were Oryzaephilus surinamensis L., Lasioderma serricorne Fab., and Cryptolestes pusillus Shoen. Also, Tribolium castaneum Herbst, Alphitobius diaperinus Panzer, and Rhyzoperta dominica Fab were less abundant and had a lower frequency. All these species were found in raisins stored in processing plants and none were observed in the field samples. Damage range was from 25 to 100% and was related to the length of time in storage. The longer the storage time, the higher the percent damage.
Yan Wang and Stanley J. Kays
The sweetpotato weevil is the single most critical insect pest of the sweetpotato worldwide. While male weevils can be lured to traps using a synthetic female pheromone, crop losses are not adequately reduced since damage is caused by the larvae arrising from eggs laid by female weevils in the storage roots. Identification of a female attractant could greatly enhance the control of the insect. The leaves and storage roots are known to emit volatiles that attract the female and in the following tests, we demonstrate that feeding by female weevils stimulates the synthesis of a volatile attractant which attracts additional females to the root. Undamaged, artificially damaged, and female weevil feeding damaged periderm were tested in dual-choice and no-choice olfactometers. Volatiles from feeding damaged roots were significantly more attractive than undamaged and artificially damaged roots. To test whether the volatile attractant was of weevil or root origin, volatiles were collected in MeCl2 after removal of the weevils and fractionated on a megabore DB-1 capillary column using a GC fitted with a TC detector. Fractions were collected from the exit port and their activity index (AI) determined using dual choice and no choice olfactometry. The active fraction was ascertained and active components identified via GC-MS.