EDITOR'S NOTE: For additional articles from the March 1997 Spring Technical Guide from Lawn & Landscape magazine, please click the following links:
- Spring Technical Guide: PHC - Making Plant Health Care Work
- Spring Technical Guide: 6 Turf Diseases and Their Cures
- Spring Technical Guide: Managing Plant Health Through Better Root Growth
Research into the use of biological controls has benefited from the push for natural, less toxic pest control products, but research efforts are by no means new. Universities and manufacturers have been trying to harness the power of nature’s pest controls for decades.
Biological control methods work extremely well under ideal, or close to ideal, conditions. The problem has been translating laboratory results into commercially usable recommendations for professional turf managers.
Research programs are testing the mettle of a variety of organisms, including entomopathogenic nematodes, bacteria, fungi, viruses and rickettsias (organisms that have characteristics of both bacteria and viruses) trying to find the best mix of the most desirable characteristics — quick and easy to establish, long lasting and predictable product.
It’s a difficult challenge. By their nature, biological controls are more affected by the destabilizing effects of nature — water, sunlight, temperature extremes and other organisms. Scientists have found some products and methods with potential, but there is still much to learn.
BACTERIA FOR GRUBS. A promising biological control for turf insects that is actively being researched is the organism Bacillus thuringiensis, known commonly as “Bt.” Discovered in Japan at the turn of the century, Bt varieties have been used to control pests such as caterpillars, fly and beetle larvae and other pests, but have not been embraced in the commercial market.
The biggest problems with Bt have been slow activity, short residual and its inability to control larger larvae, said Mike Villani, associate professor in the department of entomology at Cornell University. He also noted that Bt fails to reproduce itself once inside an insect, making it viable only for short-term control.
In ideal conditions, the bacterium will produce a protein crystal that is toxic to the insect, causing the target insect to stop feeding. Villani said that susceptible insects will die two to seven days after ingesting the Bt-produced toxin.
In recent years, researchers turned their attention to a strain of Bt known as japonesis variety ‘buibui,’ due to its activity against grubs. Mike Klein, research entomologist with the U.S. Department of Agriculture Research Service at the Ohio Agricultural Research and Development Center in Wooster, Ohio, said lab tests have shown the organism is effective in the control of Oriental and Japanese beetle grubs. To gain acceptable control, Klein said that the product must be applied in the spring and early summer when first and second instar grubs are feeding.
Still, the buibui strain is limited in the number of grubs it controls, particularly the European chafer that is fast spreading in the Northeast. Klein has been studying 10 other strains of Bt to find one that meets the professional criteria for length of control, activity and control of a broader spectrum of grubs.
| Promising Biological Controls Being Studied | |||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||
SENSITIVE NEMATODES. Entomogenous nematodes, those which feed on insects, have also shown great promise within the confines of the lab in terms of grub and caterpillar control. Villani noted that nematodes have been attractive as a research subject because of their broad range of target hosts that does not include plants or animals and their ease of production.
The effectiveness of nematodes as a biological control is a function of both the nematode used and the conditions and methods used for applying the organisms to turf. Villani noted that the nematodes Steinernema glaseri and Heterorhabditis bacteriophora are most effective against white grubs due to their ability to move into the soil and search for target insects. The more commonly available Steinernema carpocapsae has proven most effective against billbugs, cutworms, webworms and armyworms.
Critical conditions include sunlight, irrigation and storage. Nematodes are highly sensitive to sunlight and will desiccate without proper moisture. Villani suggests that they be applied early or late in the day and irrigated with ½ inch of water. It’s also critical to follow the storage and application recommendations to make sure the organisms stay as active as possible.
Harry Kaya, professor of entomology at the University of California, Davis, has been trying to increase the efficacy of nematode applications by combining species into a sort of “cocktail.” He has also combined Bt strains with nematodes in combination applications, and has had some promising results.
“We’ve found that the more grubs are stressed, the higher the mortality rates are when nematodes are applied,” said Kaya. “We are trying to use the Bt to place additional stress on the grubs to increase the potential for mortality.”
Control as high as 80 percent has been achieved, and it appears that mortality is a result of both the individual control products and the combination of each product’s activity, he explained.
Kaya is also looking at the behavioral as-pects of nematodes. Some species display the ability to jump, and he is trying to determine if this ability is linked to the nematode’s search for insect pests. Theoretically, this would make them better grub predators.
MILKY SPORE RESULTS. The use of milky spore disease against the Japanese beetle grub has been the subject of research and debate for decades. Klein has been looking at it for a quarter century.
Milky spore disease, first researched in Virginia, provided some amazing results in initial testing after its discovery. Part of the reason for its high activity back then, said Klein, was that it was tested on highly infested plots. Unfortunately, the disease has not been nearly as effective in controlling smaller levels of infestation that still damage turf. In addition, keeping populations of milky spore disease significant and viable has also been a challenge.
Despite the difficulties, Klein said that work will continue on finding the best fit for milky spore disease as a Japanese beetle grub control product.
FUNGUS AMONG US. One of the most effective pest controls in nature is the fungus. Nearly every group of turfgrass pest is susceptible to some form of fungus, according to Villani.
Lab tests have reproduced the natural pest control effect of the organisms, but producing a commercially viable fungal pathogen has been a different challenge altogether.
Two promising organisms, Beauveria balliana and Metarhizium anisopliae, are among the most extensively researched. Beauveria has good activity on chinch bugs, while certain isolates of Metarhizium anisopliae have been tested against Japanese beetle grubs.
Fungi are different, Villani said, because they do not need to be ingested by a target pest to be effective. A fungal spore attaches itself to its target and penetrates the circulatory system of the insect. Then, it uses the host as an incubator to reproduce within the insect, causing the insect to die. The resulting spores are then released to infect other target pests.
It’s too soon to tell whether fungi can be reproduced effectively and cost efficiently, or whether they can be used with the confidence that they will work consistently. More varieties and strains of fungi are being analyzed to get a better grasp on their potential as a natural pest control product, noted Villani.
The author is Managing Editor of Lawn & Landscape magazine.
Explore the March 1997 Issue
Check out more from this issue and find your next story to read.
Latest from Lawn & Landscape
- Echo reveals blowers, mowers and more at Power-On-Athon
- Lake Zurich mayor honors Echo as green business
- Echo's sustainable regrind process
- Green Lawn Fertilizing/Green Pest Solutions names Willey as president
- ASV debuts VT-80 compact track loader
- Luke Williams joins Focal Pointe as CFO
- Ford debuts 2025 Ford F-Series Super Duty
- TCO for trimmers and edgers
