Search Results

You are looking at 1 - 10 of 134 items for :

  • "hydrophobicity" x
Clear All
Free access

D.M. Glenn, G. Puterka, T. van der Zwet and R. Byers

Fruit production requires extensive use of pesticides to control pest damage and maintain high product quality. Hydrophobic particles alter the leaf surface due to the hydrophobic and reflective nature of the particles and impart characteristics that make the plant surface incompatible, and/or unrecognizable to the pest. Hydrophobic particles were applied to apple and pear in field and greenhouse studies. Specific diseases, insect pests, plant growth, and yield were monitored and evaluated on treated plants in comparison to untreated and chemically treated controls. Powdery mildew in apple and Fabrea leaf spot in pear were controlled by the hydrophobic particles. Aphids, mites, and psylla were controlled in apple and pear. Hydrophobic clays have the potential of cross-protection for several disease and insect pests while imparting beneficial horticultural effects that would increase long-term productivity and sustainability of fruit production systems.

Free access

Fumiomi Takeda, D. Michael Glenn and Thomas Tworkoski

Three experiments were performed to determine the effect of amending the soil surface layer and mulching with hydrophobic kaolin particle on weeds and blackberry (Rubus subgenus Rubus Watson) plants. In the first study a processed kaolin material (product M-96-018, Engelhard Corporation, Iselin, N.J.), was incorporated in August into the top 3 cm of freshly roto-tilled field that had been in pasture the previous 5 years. The following spring, dry weight of weed vegetation in the control treatment was 219 g·m–2 and was significantly higher (P = 0.05) than the 24 g·m–2 harvested from the treated soil. In two other studies, planting holes for blackberry transplants were either 1) pre- or postplant mulched with a 2- or 4-cm layer of 5% or 10% hydrophobic kaolin in field soil (w/w), or 2) postplant treated with a) napropamide, b) corn gluten meal, c) a product comprised of hydrous kaolin, cotton seed oil, and calcium chloride in water (KOL), d) hand weeded, or e) left untreated. Although untreated plots had 100% weed cover by the end of July, herbicide treatments, 4-cm deposition of hydrophobic kaolin particle/soil mulch, and KOL all suppressed weeds the entire establishment year. Preplant application of hydrophobic kaolin mulch and postplant application of KOL reduced blackberry growth and killed transplants, respectively. In year 2, blackberry plants produced more primocanes that were on average 10-cm taller in weed-free plots (herbicide, 4-cm kaolin soil mulch, and mechanical weeding) than in weedy plots (control and 2-cm kaolin soil mulch). In year 3, yield was significantly lower in control plots (1.5 kg/plant) than in plots that were treated with napropamide and 2- and 4-cm hydrophobic kaolin mulch, or hand weeded during the establishment year (4 kg/plant). The results showed that 4-cm hydrophobic kaolin mulch applied after planting can suppress weeds without affecting blackberry productivity. These kaolin products are excellent additions to the arsenal of tools for managing weeds in horticultural crops.

Free access

Michael Wisniewski, D. Michael Glenn and Michael P. Fuller

Extrinsic ice nucleating agents (such as ice-nucleation-active bacteria, dew, etc.) significantly limit the ability of herbaceous plants to supercool. It is believed that with an absence of these extrinsic nucleating agents, a plant could supercool to less than -4 °C. Other evidence, however, indicates that intrinsic nucleating agents may limit the extent of supercooling. Infrared video thermography was used to study freezing in young, `Rutgers' tomato (Lycopersicon esculentum L.) plants and to determine if a hydrophobic barrier on the plant surface could prevent extrinsic nucleating agents such as Ice+ bacterial strain (Cit7) of Pseudomonas syringae Van Hall from initiating freezing within a plant. Freezing tests were conducted in a programmable freezing chamber, a radiative frost chamber, and outdoors. Freezing was visualized and recorded on videotape using an infrared radiometer. Freezing of the plants was induced extrinsically by application of droplets (5 to 7 μL) of water containing Cit7. To provide a barrier to the action of extrinsic ice nucleating agents, an emulsion of hydrophobic kaolin (aluminum silicate mineral) was applied to the plant surface before application of an extrinsic nucleating agent. Results indicate that dry, young tomato plants can supercool to as low as -6 °C whereas plants having a single droplet of Cit7 would freeze at -1.5 to -2.5 °C. Application of the hydrophobic barrier blocked the effect of Cit7 and allowed whole plants to also supercool to -6 °C, despite the presence of frozen droplets on the leaf surface. When whole plants were sprayed with water and Cit7 using an aerosol sprayer and exposed to -3 °C, plants coated with the hydrophobic particle film exhibited significantly less foliar injury then nontreated plants. Similar results were obtained using the radiative frost chamber. Experiments conducted under natural frost conditions also resulted in less injury to the coated plants. The hydrophobic kaolin particle film performed better at preventing plants from freezing due to extrinsic ice nucleation than nonaltered, hydrophyllic kaolin alone or an antitranspirant with putative frost protection properties.

Free access

Michael Wisniewski, Michael Glenn and Mick Fuller

Most plants exhibit the ability to supercool to some extent without freezing. The extent of supercooling, however, is limited by the action of intrinsic and extrinsic ice nucleating agents which initiate ice formation and propagation within a plant at relatively warm subzero temperatures (-1.5 to -3.5 °C). In herbaceous plants, extrinsic ice-nucleating agents (such as ice-nucleation bacteria, dew, and other good nucleating agents) significantly limit the ability to supercool below 0 °C. It is believed that with an absence of these extrinsic nucleating agents that plants could supercool to less than -4 °C. Other evidence indicates that intrinsic nucleating agents may also significantly limit the extent of supercooling. Questions also exist about nucleation in woody plants and especially the new growth (flowers, leaves, and shoots) present in spring. A better understanding of how freezing is initiated in plants has been limited by the inability to determine and visualize the initial site of ice nucleation and pattern of ice propagation. We have used infrared video thermography to study freezing in young tomato (Lycopersicon esculentum) plants and to determine if a hydrophobic barrier on the plant surface could prevent the action of extrinsic nucleating agents such as Ice + bacterial strain (Cit7) of Pseudomonas syringae from initiating freezing within a plant. Tomato plants were grown in a greenhouse in individual pots and used when they were 4 to 6 weeks old. Freezing tests were conducted in a programmable freezing chamber, and freezing was visualized and recorded on videotape using an infrared radiometer. Freezing of the plants was extrinsically induced by the application of droplets (5 μl) of water containing Cit7. To provide a barrier to the action of extrinsic ice-nucleating agents, an emulsion of hydrophobic kaolin was applied to the plant surface before applying an extrinsic nucleating agent. Results indicate that dry, young tomato plants can supercool to as low as -6 °C whereas plants having a single droplet of Cit7 would freeze at -1.5 to -2.5 °C. Applying the hydrophobic barrier blocked the effect of Cit7 and allowed the plants to also supercool to -6 °C, despite the presence of frozen droplets. Experiments under natural freezing conditions are in progress.

Open access

Michael Fidanza, Derek Settle and Henry Wetzel

The term “fairy ring” typically refers to the visual appearance of mushrooms emerged in a circular pattern in a grass lawn, pasture, or meadow. Fairy ring symptoms in turfgrass stands are categorized as Type I (wilted, necrotic turf), Type II (dark green, stimulated turf), and Type III (basidiocarps present). A visual rating system was devised to assist researchers and practitioners with a numerical method to quantify the degree of severity of fairy ring symptoms at a turf site. Therefore, the Fairy Ring Severity Index is based on a 1 to 9 scale, where 1 indicates no fairy ring symptoms present, 2 through 5 indicates the low to high range for Type II symptoms, and 6 through 9 indicates the low to high range for Type I symptoms. For Type III symptoms, the number of mushrooms, toadstools, or puffballs present could be counted if that information is needed or helpful. In experimental research plots, the Fairy Ring Severity Index is a better method for evaluating and comparing fairy ring symptoms vs. using a percent plot area affected estimate.

Free access

Lusheng Zeng, Jiayang Liu, Robert N. Carrow, Paul L. Raymer and Qingguo Huang

Soil water repellency (SWR) is a condition in which a soil does not spontaneously wet when a drop of water is applied to the surface, indicating that the soil is hydrophobic ( Müller and Deurer, 2011 ). In recent years there has been greater

Free access

Michael Wisniewski, D. Michael Glenn, Lawrence Gusta and Michael P. Fuller

). The implication of this research was that if one could effectively block the growth of external ice crystals into the interior of the plant, the plants would supercool several degrees without freezing. HYDROPHOBIC BARRIERS CAN BLOCK ICE

Free access

Jeb S. Fields, William C. Fonteno and Brian E. Jackson

(OM) components in them. These components, primarily composed of sphagnum peatmoss and pine bark, can become hydrophobic, thus reducing wettability ( Dekker et al., 2000a ; Michel et al., 2001 ). The molecules of OM contain many organic acid

Free access

Rebecca C.-C. Hsu and Yung-I Lee

materials, or lignin, may deposit on the seedcoat and contribute to the hydrophobic nature of mature seeds ( Carlson, 1940 ; Lee et al., 2005 ; Yeung et al., 1996 ). These factors may bring about the impermeability of mature seeds and result in low seed

Free access

Jeffrey A. Anderson

exposed hydrophobic patches, preventing aggregation or misfolding of partially unfolded proteins (“molecular chaperone” activity) ( Jacob et al., 1995 ). Chemical chaperones appear to maintain native protein structure through interactions with the protein