D. Michael Glenn

Progress Toward Liquid Formulations of Particle Films for Insect and Disease Control in Pear

Abstract Particle film technology is aimed at controlling both arthropod pests and diseases of plants with a hydrophobic particle barrier primarily composed of kaolin. Field studies were conducted from 1996 to 1998 to compare the efficacy of dust and liquid applications, and hydrophobic and hydrophilic particle films, against key pests of pear. In addition, the effects of particle film applications on pear yield and quality were investigated in 1998. Dust and liquid applications of hydrophobic and hydrophilic particle films obtained high levels of early-season pear psylla control and prevented pear rust mite damage. We also found that prior seasonal applications of particle films in 1997 can carry over into the 1998 season to suppress early season pear psylla oviposition. A major concern in the shift from hydrophobic to hydrophilic particle films was the loss of disease control. We found that a water-repellant particle film was not required to control the fungal disease fabraea leaf spot. Pear yields were nearly doubled by liquid formulations of hydrophobic and hydrophilic particle films. Particle film deposits were measured using a spectrophotometer method we developed. Particle deposition differed among formulations for both leaf age and leaf surface (top or bottom). Yet, the particle formulations performed about the same against insects and fungal diseases, and in how they influenced the horticultural traits. None of the particle film formulations were found to be phytotoxic to pear foliage or fruit during the study period. A shift from hydrophobic to hydrophilic particles makes it possible to more easily formulate and disperse the particles in water so that conventional spray equipment can be used. The multifunctionality and low toxicity of particle films could make them an attractive alternative to conventional pesticides.

Aquaculture sludge removal and stabilization within created wetlands

The objective of this research was to investigate treatment of the concentrated solids discharge produced during clarifier backwash within an aquaculture facility. Solids removal and stabilization were investigated within two types of created wetlands where water flowed either: (1) vertically, down through a porous substrate; or (2) horizontally, over soil and through plant hedges. Six 3.7×1.2×0.8-m (L×W×H) wetland cells were used to provide three replicates for both types of wetland. Approximately equal numbers of vetiver grass (Vetiveria zizanioides) tillers were planted on both wetlands types in November of 1994. Sludge (7500 mg l−1 solids) was loaded onto both wetland types six times day−1, with no scheduled drying cycle, from 12 May 1995 until 28 February 1996. Sludge was applied at a rate of about 1.35 cm day−1, or about 30 kg dry solids m−2 year−1. Results from this short study indicated that the vertical flow and horizontal flow wetlands, respectively, removed 98 and 96% TSS, 91 and 72% total COD, and 81 and 30% dissolved COD. Both types of wetland cells removed most (82–93%) of the total kjeldahl nitrogen, phosphorus, and dissolved phosphate. Measurements of sludge depths and TVS at the end of the study indicated considerable mineralization occurred in the wetlands; stored sludge at the end of the study had 50% less TVS than untreated sludge.

Mechanistic approach to phytoremediation of water

Conventional thinking regarding the use of food crops to clean aquaculture effluents has been that plants cannot remove nutrients in water to low levels without a reduction in productivity and quality. Because greenhouse space is expensive, productivity is critical for a profitable operation. A production strategy, called the conveyor production system (CPS), was developed using thin-film technology for plant production in dilute aquaculture effluents. With the CPS, young plants were positioned near the solution inlet in a gutter receiving the effluent and moved progressively, like along a conveyor belt, towards the outlet as they grew. Luxury consumption by lettuce plants (Lactuca sativa L. cv. Ostinata) enabled them to store P in their tissues early in their growth cycle for use later as water P levels decreased and influx could no longer meet current demands. If water is distributed in a horizontal plug-flow pattern, without the CPS, all nutrients will be luxury consumed at the inlet, making nutrients limiting at the outlet and significant greenhouse space will be dedicated to growing plants that have no market value. The object of this study was to construct and operate a pilot-scale CPS, collect data demonstrating its potential to clean effluent and produce a marketable product, and develop a mechanistic model describing the process. Greenhouse studies demonstrated that by using the CPS, phosphorus could be reduced from 0.52 to <0.01 mg l−1 by lettuce without an apparent reduction in production or quality. The mechanistic model described in this paper simulated experimental data collected during the operation of the CPS growing lettuce and defines critical data necessary for the general comparison of effluents for treatment.

Response of bean to applications of hydrophobic mineral particles

Foliar applications of hydrophobic mineral particles can protect plants from some insects, but plant response to particle applications is not known. Bean (Phaseolus vulgaris L.) plants were grown for 8 wk in a greenhouse and the shoots were sprayed weekly with small-diameter hydrophobic mineral particles. Photosynthesis was similar in particle-treated and control bean plants over a photosynthetic photon flux (PPF) range from 0 to 1548 µmol m–2 s–1. The shoot-to-root dry weight ratio was 56% greater and pod weight was 20% lower in particle-treated plants than control plants, suggesting that particle films may alter dry weight partitioning of plants. In bean, particle residues of 2.71 mg cm–2 leaf area altered plant development without affecting photosynthesis. Key words: Phaseolus vulgaris, crop protection, photosynthesis, dry weight distribution, kaolin

Effect of Surround WP on Behavior and Mortality of Apple Maggot (Diptera: Tephritidae)

ABSTRACT Apple maggot, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae), is a key pest in apple (Malus spp.) production areas located in the northeastern and midwestern United States and the eastern provinces of Canada. The development of Surround WP has offered a new approach for controlling apple maggot and other tephritid species, because this material is considered to be compatible with advanced integrated pest management and organic production systems. We conducted studies aimed at identifying the behavioral and biological effects of this material on apple maggots. Specifically, we examined the effect of Surround WP on the visual ecology of adult flies under field conditions, on tactile responses of flies in semifield trials, and on fly mortality in laboratory-based-bioassays. We demonstrated that an even coating of white particles over a fruit-mimicking sphere surface reduced visual attractiveness. We also found that spotty-coated fruit-mimicking spheres (meant to mimic ripe fruit bearing an uneven coating of Surround WP) were perceived by flies as not having the ideal round silhouette shape stimulus. Surround WP served as a tactile deterrent; the residence time of females introduced on to treated fruit was much shorter compared with untreated fruit. Surround WP also had a toxic effect on both adult apple maggot and Rhagoletis suavis (Loew); flies exposed to and forced to stand on Surround-treated surfaces died in <2 d in all trials. The combined effectiveness of Surround WP is based on a reduction in the attractiveness of fruit-based visual cues, an increase in the likelihood of flies leaving treated surfaces due to tactile deterrence, and a potential for increased mortality due to exposure to Surround WP particles.

Behavioral Responses of the Invasive Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) to Light-Based Stimuli in the Laboratory and Field

Halyomorpha halys (Stål), brown marmorated stink bug, is an invasive insect native to Asia that was accidently introduced into the United States. The species is a polyphagous pest that has caused serious economic injury to specialty and row crops in the mid-Atlantic region. Growers have targeted H. halys with broad-spectrum materials by increasing the number of and decreasing the interval between insecticide applications. While it is known that adults reliably respond to semiochemical cues, much less is known about the response of H. halys to visual stimuli. Field observations suggest that H. halys adults respond to light-based stimuli, with large aggregations of adults documented at outdoor light sources and captured in commercial blacklight traps. Therefore, we conducted a series of studies aimed at identifying optimal wavelengths and intensities of light attractive to H. halys adults. We found that intensity and wavelength of light affected H. halys response in the laboratory and field. In the laboratory, H. halys demonstrated positive phototactic responses to full-spectrum and wavelength-restricted stimuli at a range of intensities, though the levels of stimulus acceptance and attraction, respectively, changed according to intensity. The species is most attracted to white, blue and black (ultraviolet) wavelength-restricted stimuli in the laboratory and field. In the field, traps baited with blue light sources were less attractive to non-target insect species, but white light sources were more attractive to H. halys indicating that these two light sources may be good candidates for inclusion in light-based monitoring traps.

Extrinsic Ice Nucleation in Plants

In the early 1980s a considerable amount of research focused on the role of extrinsic ice nucleation and its= role in inducing plants to freeze at warm sub-zero temperatures. The working hypothesis was that by controlling extrinsic nucleation events, plants could supercool well below 0 °C and thus avoid freezing (Lindow, 1995). It was felt that such a strategy could provide a significant level of frost protection to frost sensitive plants or plant parts. While the majority of reports dealt with the role of ice-nucleating-active (INA) bacteria (e.g. Pseudomonas syringae), related research focused on the role of other extrinsic nucleating agents and whether or not plants could actually supercool to temperatures several degrees below 0 °C due to the presence of intrinsic nucleating agents which induced the plants to freeze at warm temperatures (Ashworth and Kieft, 1995). The identification of a wide range of both extrinsic and intrinsic ice nucleating agents made the practical application of blocking extrinsic ice nucleation complex. Since that time, research emphasis has switched to identifying genes that impart cold tolerance and the transcriptional activators that regulate cold hardiness genes (Thomashow, 1998; Jaglo, et al., 2001). The hypothesis here is that by the overexpression of these types of genes, a non-acclimated or freeze-sensitive plant could be made freezing tolerant.While great progress has been made in understanding the genetic basis of cold hardiness, manipulation of this trait by molecular biology has also demonstrated itself to be complicated due to the “additional” effects of the overexpression of several cold hardiness genes on the physiology and development of the target plant. Therefore, blocking extrinsic ice nucleation, although complicated, may still be a valuable approach to providing protection to frost sensitive plants.

Weed Suppression by Grasses for Orchard Floor Management

Abstract Fruit trees in orchards of the mid-Atlantic region of the United States are often planted in vegetation-free rows alternating with grass alleys. Grass managed to suppress weeds but to compete minimally with fruit trees may be an alternative to herbicide and tillage. This research was conducted in the greenhouse and field to assess five different grasses that may suppress weeds without reducing yield of fruit trees. In the greenhouse with high seeding rates, red fescue competed more effectively than did chewings fescue, tall fescue, and perennial ryegrass with three weeds (damesrocket, cornflower, and chicory). However, with reduced seeding rates, similar to rates used in the field, grass competitiveness with weeds was similar between red fescue, tall fescue, and perennial ryegrass. Similar results were obtained during a 4-yr field experiment; roughstalk bluegrass competed least effectively with weeds but the other four grasses provided similar weed suppression—generally providing as much weed suppression as traditional herbicides. None of the candidate grasses significantly reduced yields of 10-yr-old apple and peach trees, although fruit size was affected by some grasses. The grass that was least suppressive of yield, roughstalk bluegrass, was the least effective in controlling weeds. Annual mowing in combination with four of the grasses tested is one option to manage the orchard floor with reduced herbicides, but fruit size may decrease. Nomenclature: Chicory, Cichorium intybus L.; cornflower, Centaurea cyanus L.; damesrocket, Hesperis matronalis L.; apple, Malus × domestica Borkh.; chewings red fescue, Festuca rubra var. commutata L. Gaudin; peach, Prunus persica (L.) Batch; perennial ryegrass, Lolium perenne L.; red fescue, Festuca rubra L.; roughstalk bluegrass, Poa trivialis L.; tall fescue, Lolium arundinaceum (Schreb.) S.J. Darbyshire.

Growth of apple trees, nitrate mobility and pest populations following a corn versus fescue crop rotation

We compared conventional and alternative systems for the establishment of apple trees on a replicated, whole-orchard scale. The alternative system consisted of a K-31 fescue sod rotation followed by planting of trees directly into sod that had been kitted with herbicide. The conventional system consisted of a standard corn rotation, accompanied by application of fertilizer and nematicide. Orchard floor management in the three years following tree planting was based on the use of both pre-and post-emergence herbicides in the conventional system and only contact herbicide in the alternative system. The study documented tree growth, pest incidence, and nitrate mobility in the two systems. The alternative system compared favorably with the conventional system for the growth and establishment of four apple cultivars. Many advantages accompanied the killed sod system, including less subsurface leaching ofnitrate-N and lower costs (largely from decreased herbicide use). The alternative system provided an economical alternative to the problem of soil organic matter depletion in conventional orchard soils without requiring increased use of commercial fertilizers. Grower concerns regarding increased potential for vole damage and poor initial tree growth were unsubstantiated.

Response of Young Apple Trees to Grass and Irrigation

ABSTRACT Ground covers and irrigation are important components of orchard floor management systems that affect fruit tree vigor and productivity. Three experiments were conducted in a greenhouse to determine the relative water use of candidate ground covers (roughstalk bluegrass, RB, Poa trivialis), Chewings fescue (CH, Festuca rubra subsp. commutata Gaudin), creeping red fescue (RF, Festuca rubra L. subsp. rubra), tall fescue (TF, Festuca arundinacea Schreber, Fawn), and perennial ryegrass (PR, Lolium perenne L., ‘Saint’) and the response of apple trees to those ground covers and to drip irrigation applied at two soilless substrate depths. Grass ground covers with large and deep root systems (TF and PR) used more water than a shallow- rooted grass (RB) and leaf water potential decreased more rapidly in apple trees grown with TF than RB when irrigation was withheld. Although apple tree shoot growth was greater with shallow- than deep-rooted grass, photosynthesis, transpiration, and root biomass distribution were not differentially affected by grass type. When grown with RB or TF, irrigation depth affected apple tree growth. During the first season in the greenhouse, deep irrigation at 37 cm depth increased apple root length density near emitters but shoot growth was less in apple grown with deep irrigation compared with apple grown with surface irrigation (0 cm) and with split irrigation at 0 and 37 cm. During the second season in the greenhouse, deep irrigation was beneficial to trees grown with grass that had large, deep root systems (TF) but it did not completely overcome interference effects of grass on apple trees, regardless of grass root system size or distribution. The results indicate that grasses with shallow root systems may be grown beneath apple trees and that split irrigation at two depths can provide flexibility that is necessary for water management of ground covers and apple trees.