Laboratory Report

By: Robert D Raabe

Robert D Raabe is Professor Emeritus of Plant Pathology at University of California, Berkeley. He introduced a faster method of…

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Formosan Termite Control

The Formosan termite (Coptotomes formosanum) causes an estimated $1 billion cost, annually, in property damage and for preventative measures and structural repairs. In the southern and southwestern states, this termite is unrivaled in colony size. It attacks service lumber as well as living trees. Termite repellants cause them to move to other locations, and insecticides are slow acting. Researchers in Illinois and New Orleans, working with a fungus (Paecilomyces formosanosens), knew its effectiveness in attacking and killing termites but needed an effective way to apply it. After they experimented with more than a dozen foaming agents, they found a commercially available protein, keratin hydrolysate, that was compatible with the fungus and allowed the fungus to be more effective than when applied in water. In the foam, made of a mixture of keratin hydrolysate, water, fungus spores, nutrients, and adjuvants (which help the spores stick to the termites), the spores germinated faster. The mix is sprayed into termite holes; after twenty-five minutes, the foam collapses. The termites pick up the spores directly from the foam or as they are foraging or grooming each other. A patent has been applied for. Agricultural Research 55 (8): 4-6.

Varroa Control

One approach to control Varroa mite, an important pest of honey bees, is to use resistance. Researchers in Louisiana have released commercial queen bees from a line of honey bees found in Russia that are resistant to the mites. Colonies with Russian queens produced sixty-four pounds of honey per hive; non-Russian colonies averaged seventy-eight pounds per hive. The price difference would be $17 per year per colony. However, the cost of mite control is $18-20 per year, so the use of Russian bees is economically feasible. Beekeepers are becoming more familiar with management of the Russian bees, and researchers have shown that, properly managed, Russian colonies can be as productive as non-Russian colonies. Louisiana Agriculture 50 (3): 8-11.

Scent Marking of Flowers

Researchers in Texas have noted that female bees of Xylocopa virginiana subsp. texana made two kinds of visits to flowers of maypop (Passiflora incarnata): a nectar visit, in which a bee landed in a flower and withdrew nectar; and an examination visit, in which a bee approached the flower, as in a nectar visit, but turned abruptly away to visit other flowers (occasionally, a bee might touch the flower slightly before flying away). The type of visit depended upon the time that had elapsed since the previous nectar visit. If that time was less than ten minutes, an examination visit followed; if more than ten minutes, a nectar visit resulted. An anatomical study of the bees showed there to be two glands associated with the reproductive structures of the bees: Dufour’s gland and a poison sack. By placing substances from each of the glands in the flowers separately, the researchers learned that the material from the Dufour’s gland was responsible for the repulsion of the bees for periods up to ten minutes, due to the scent left on the flower. These scents have no effect on any other bees or the male bees of the same species. A further literature review mentioned scent-marking by several species of social and solitary bees in the genera Bombus, Psithyrus, Melita, Anthophora, Andrena, and Anthidium. Journal of the Kansas Entomological Society 50: 613-625.

Light Brown Apple Moths

The light brown apple moth was discovered in California in February 2007. An important pest, it is known to attack at least 250 kinds of plants, many of them agricultural crops such as peaches, nectarines, plums, cherries, apricots, citrus, apples, pears, grapes, and landscape plants including cypress, redwoods, oaks and many other plants used in urban and suburban areas. It has moved into nine counties in the San Francisco Bay area. The California Department of Agriculture is using a fleet of three airplanes, targeting a sixty square mile area of Monterey County for spraying with pheromones that will confuse males and keep them from mating. Pheromone-infused plant ties will be used in residential areas. These biological controls will be enhanced by the use of Bacillus thuringiensis (Bt) sprays. It is especially serious because nursery crops that are shipped outside the infested counties will be subjected to intra-state and interstate quarantines (on top of quarantines already in place for Sudden Oak Death). California Agriculture 64 (4): 149 and Western Fruit Grower 127 (7): 6 and 127 (9): 6.

Arsenic in Kelp

California researchers have found that eight out of nine over-the-counter kelp products, obtained from health food stores, contained arsenic. Seven of the herbal supplements exceeded the arsenic tolerance levels set by the US Food and Drug Administration. UC Davis Magazine 24 (4): 7

Tropical Maize

Tropical maize, a form of corn cultivated in the tropics, was grown in Illinois to obtain a source of the genes involved in the utilization of nitrogen. Research showed that the corn required much less nitrogen than conventional corn, and, because it is a long-night plant (commonly called a short-day plant, but it is the amount of darkness that is critical), it produced no ears, resulting in a concentration of its sugars in the stalks. The sugars, mostly sucrose, fructose, and glucose, are one step closer to being turned into fuel than using conventional corn since they do not have to go through a fermentation process. Because the quantity of sugars produced is twenty-five percent or higher, the plant is called the “sugar cane of the Midwest.” Though the stalks are fourteen to fifteen feet tall, farmers can integrate the crop into their normal field rotations and use the same equipment for planting, cultivating, and harvesting. Science Daily October 7, 2007: p. 2.