Growing Tips—Cutting-Edge Plants, Tools & Techniques
Plants & Gardens News Volume 17, Number 1 | Spring 2001
by Greg and Pat Williams
Certifying Plant Imports
The U.S. Plant and Animal Health Inspection Service, which safeguards the nation's animal and plant resources from exotic invasive pests and diseases, has announced that it plans "to begin consistently and routinely enforcing an existing requirement that a phytosanitary certificate of inspection accompany restricted articles... offered for importation into the United States under our foreign quarantine regulations for nursery stock, plants, roots, bulbs, seeds, and other plant products." Though the requirement was already in place, it has never been strictly enforced until now. Both professional and amateur growers who import even very small quantities of plant material must be sure that they attach the proper legal documents in order to prevent destruction of the material at ports of entry.
To learn more, contact James Petit de Mange, CITES and Plant Inspection Station Coordinator, Port Operations, Plant Protection and Quarantine, APHIS, 4700 River Road, Unit 60, Riverdale, MD 20737-1236; 301-734-8295.
A Terrific Tomato
Photo courtesy Penn State
The new 'Penn State Cherry Tomato' cultivar is well suited to growing conditions in the Mid-Atlantic states, where temperatures are considerably lower than in California and Florida (for which most tomato cultivars are bred these days). 'Penn State Cherry Tomato' resists the fungal blights that cut Pennsylvania's annual commercial tomato yields by around 30 percent. And it has an unusually high concentration of the antioxidant lycopene, which is touted as an anticancer chemical. For more details, contact the breeder, Majid Foolad, Pennsylvania State University, Dept. of Horticulture, 217 Tyson Bldg., University Park, PA 16802; 814-865-5408.
Source: Anonymous, "New Cherry Tomato Is Fungal Resistant," Greenhouse Management & Production 21(10), October 2001, 10. (Branch-Smith Publishing, 120 St. Louis Ave., Fort Worth, TX 76104)
Validating IPM
A major part of Integrated Pest Management (IPM) is monitoring pest populations and plant damage so that pesticides are used only when and where needed. While compiling an inventory of woody plants in suburban central Maryland, researchers recently observed the negative effects that untargeted regularly scheduled pesticide spraying can have on local ecosystems. They found significant scale infestation on 75 percent of landscapes subject to this type of spraying for four years or more. In contrast, only about 40 percent of landscapes subject to scheduled sprays for fewer than four years had significant scale problems.
Thus the researchers established a correlation between scale infestation and long-term, scheduled, untargeted spraying. But they did not determine the reason for it. One possibility is that the spraying adversely affected beneficial organisms antagonistic to scale populations. The researchers recommended that, whenever possible, property owners and land managers use "well-timed spot treatments or targeted insecticide applications based on biological observations."
Source: M.J. Raupp, J.J. Holmes, C. Sadof, P. Shrewsbury, and J.A. Davidson, "Effects of Cover Sprays and Residual Pesticides on Scale Insects and Natural Enemies in Urban Forests," Journal of Arboriculture 27(4), July 2001, 203-13. (International Society of Arboriculture, P.O. Box 3129, Champaign, IL 61826)
Sharpen Those Blades!
Sharp mower blades result in better-looking lawns. That's because the grass tips are sliced cleanly instead of being torn off. But there are other, less obvious benefits of keeping blades sharp. In University of Nebraska trials, mowers with sharp blades used 20 percent less gasoline than mowers with dull blades. Also, disease incidence (in disease-susceptible cultivars only) was lower after mowing with sharp blades, perhaps because the cleaner cut allowed for less accessibility to the plants by pathogens.
Source: Anonymous, "Research Update: Sharp Blades Conserve Fuel," Grounds Maintenance 36(8), August 2001, 50. (Primedia Business, 9800 Metcalf Ave., Overland Park, KS 66212)
Paper Pot Warning
A fungus that can produce toxins harmful to humans was recently discovered on recycled paper pots in Pennsylvania. The fungus, Stachybotrys chartarum, degrades wet cellulose, creating areas of shiny and slimy black mold, sometimes edged with white. Its spores, which can disperse in the air when the fungus dries out, sometimes cause skin and mucous-membrane irritation. Thus, it is best to dispose of contaminated materials while wet. University of Pennsylvania plant pathologist Gary Moorman recommends discarding all such materials or spraying them thoroughly (and repeatedly if fungi appear again) with a solution of ¼-cup of household bleach per gallon of water.
Source: Anonymous, "Harmful Fungus Found on Recycled Paper Pots in Pennsylvania," American Nurseryman 194(5), September 1, 2001, 14. (American Nurseryman Publishing Co., 77 Washington St., Suite 2100, Chicago, IL 60602)
Natural Frost Protection
A biodegradable material developed from a deicing spray used on aircraft is now being commercialized for horticultural purposes. The new product, "Frost Bloc," is the brainchild of Genesis Agri-Products, Inc., a subsidiary of the G.S. Long Company, Inc., in Yakima, Washington. Trials in apple orchards with preliminary formulations of Frost Bloc have resulted in good protection against spring frost damage at 26°F to 28°F. Additional trials have been conducted with tomatoes, strawberries, and lettuce. The composition of Frost Bloc is a secret, but its development began with the accidental discovery that a waste product of ethanol (grain alcohol) production is a potent deicing agent. The manufacturer expects Frost Bloc to be approved for use by commercial organic growers.
Source: Rene Featherstone, "Sprayable Frost Protection May Revolutionize Fruit Industry," The Fruit Growers News 40(7), July 2001, 28, 34. (Great American Publishing Inc., 343 S. Union St., Sparta, MI 49345)
Bug-Resistant Boxwoods
The boxwood leafminer (Monarthropalpus flavus) is a common pest in the eastern United States. Its larvae tunnel into the leaves of boxwood (Buxus species), leaving them blistered, discolored, and subject to early dropping. University of Maryland entomologists surveyed nine boxwood cultivars growing in a leafminer-infested garden at the U.S. National Arboretum in Washington, D.C., for presence of eggs on leaf surfaces and for survival of larvae within leaves. The larval survival rates were "very low" for B. sempervirens 'Handsworthiensis' and 'Varder Valley', providing evidence that these two cultivars have especially high levels of resistance to the leafminer and should be favored for planting in areas where the pest is established.
Source: G. d'Eustachio and M. Raupp, "Resistance of Boxwood Varieties to the Boxwood Leafminer, Monarthropalpus flavus (Schrank)," Journal of Environmental Horticulture 19(3), September 2001, 153-57. (Horticultural Research Institute, 1250 I St., N.W., Suite 500, Washington, DC 20005)
Mulch Fights Fungus
University of California researchers investigated the effects of organic mulch (in this instance, freshly chipped trimmings from blue gum trees) on root rot due to the Phytophthora cinnamoni fungus, which can cause serious problems for ericaceous plants such as rhododendrons, azaleas, and andromedas. They found that the death rate of the fungus was, in general, significantly higher in the mulch layer than in mineral soil. They also found that P. cinnamoni fungi tend to die in large numbers at the interface between the soil and mulch. Certain cellulose-degrading enzymes in the mulch layer appeared to be toxic to the fungus. The mulch layers used in the university trials were about six inches deep, simulating the thick mulch layers found in rainforests, where Phytophthera fungi fare poorly.
Source: A.J. Downer, J.A. Menge, and E. Pond, "Association of Cellulytic Enzyme Activities With Biological Control of Phytophthora cinnamoni," Phytopathology 91(9), September 2001, 847-55. (American Phytopathological Society, 3340 Pilot Knob Rd., St. Paul, MN 55121)
The Wonders of Watercress
In a comprehensive review article on watercress (Rorippa nasturtium-aquaticum), University of Connecticut researchers praised the vegetable's anticancer properties. The pungent flavor of watercress is due mainly to a chemical, PEITC, which is known to inhibit various types of cancer. Watercress also has considerable concentrations of several vitamins and minerals essential for a healthy diet. For highest PEITC concentrations—and for the hottest flavor—the researchers recommend that watercress be harvested when there are 12 to 15 internodes (areas between leaf buds) along each stem. Watercress can be stored for up to a month in polyethylene bags at 32°F and approximately 95 percent relative humidity.
Source: U.R. Palaniswamy and R.J. McAvoy, "Watercress: A Salad Crop With Chemopreventive Potential," HortTechnology 11(4), October-December 2001, 622-26. (American Society for Horticultural Science, 113 S. West St., Suite 200, Alexandria, VA 22314)
Regular contributors to P&G News, Greg and Pat Williams practice what they preach: Many of the growing tips they collect for their P&G columns are put to use on their farm in Gravel Switch, Kentucky. The couple are also the editors of HortIdeas.