January 18, 2007
Mr. Gary Sykes
Executive Director, NERTF
28 Pelham Street
Newport, RI 02840
Dear Gary and the NERTF Grant Review Committee:
In 2005, Andrea Bixby was admitted as a Masters Degree candidate in the Department of Plant Sciences at the University of Rhode Island. Funds from the grant were used to fund Andrea and the research project.
Entomopathogenic Nematodes
Two commercially available strains of Heterorhabditis bacteriophora were obtained from Becker-Underwood and applied 25 August 2005 to fine fescue infested with oriental beetle larvae. Strain #1 provided 95% control of larvae, strain #2 provided 83% control of larvae. The nematodes were as good as or better than two standard insecticides (Merit 83% control; Dylox 53%) (Fig. 1).
Oriental Beetle Mating Disruption
In a mating disruption experiment, six traps baited with 30 ?g of pheromone were placed in a landscape known to be infested with oriental beetles. Traps were changed and beetles captured were counted weekly throughout the flight period for three years. 9,199 beetles were captured over the flight period in 2004; 42,763 beetles were captured in 2005 and 26,899 beetles were captured in 2006. Cup changer samples of the turf in the fall of 2004, 2005 and 2006 revealed no oriental beetle larvae. One hypothesis is that the high concentration of pheromone in an area repells other females from laying eggs in that area. Female marking an egg laying site has been documented for other insect species. Commercial formulations are being developed for pheromone disruption of oriental beetles for use on turf and blueberries.
Milky Disease (Field Studies)
In 2004, we established milky disease, Paenibacillus popilliae, in turf known to be infested with Japanese beetles. The unique aspect of the milky disease establishment was that every square centimeter in our 4' X 4' plots received an "effective" dose of bacteria. Plots evaluated in the fall of 2005 and 2006, one and two years after establishment, showed no statistically significant difference between treated and control plots (Fig. 2). Soil temperatures and moisture levels were measured one and two inches below the surface of the turf during the time that grubs are present (Fig. 3 and 4). These measurements show that this experiment was conducted in an area with soil temperatures that are supposed to be conducive to milky disease infectivity (i. e. > 21oC).
Milky Disease (Laboratory Studies)
In 2006 laboratory experiments were conducted using third instar Japanese and oriental beetle larvae. Commercial spore powders from St. Gabriel Laboratories (Orange, VA) and Fairfax Biological Laboratory, Inc. (Clinton Corners, NY), were mixed into a soil and seed mixture. Grubs were confined in this mixture and incubated at 30º C. There were no significant differences in the percentage of infected oriental or Japanese beetle grubs in the treated soil vs. the untreated soil after 30 days (Fig. 5A). Aqueous suspensions of the commercial spore powders and spore suspensions made from milky disease infected oriental and Japanese beetle larvae collected from the field, were injected into larvae. Suspensions were injected into the midgut (peroral injection) or directly into the hemocoel (body cavity) of the grubs (intrahemoceolic injection). No significant differences were seen when suspensions were injected directly into the midgut of Japanese or oriental beetles when compared to the control (Fig. 5B, D, E, and F). There was a significant difference when the spore suspension made from infected oriental beetle larvae was injected directly into the hemoceol of the oriental and Japanese beetle (Fig. 5E and F). There was also a significant difference when the aqueous suspension made from Fairfax spore powder was injected directly into the hemocoel of the Japanese beetle at 30º C, but not at 24º C (Fig. 5C). Larvae did not appear to be milky prior to use in experiments, but after 30 days at 30º C, grubs even in the control group became infected. Larvae have a higher infection rate when held at 30º C than 24º C.
Bacillus thuringiensis japonensis
Since the start of research on this grant, another bacterium (Bacillus thuringiensis japonensis strain Buibui) has become available for testing. Since we demonstrated good control of white grubs with nematodes and there are commercially available sources, with the permission of NERTF, we put more emphasis in assessing the potential of this promising control agent. We have completed thirteen different experiments with this strain versus oriental, Japanese, European chafer, and Asiatic garden beetle larvae. Rates as low as 100 g toxin / ha were effective versus oriental and Japanese beetle larvae (Figs. 6 and 7). Rates of 100 - 600 g toxin / ha were not effective versus European chafer or Asiatic garden beetle. We are working with a company to get this product registered in the U. S.
Summary
The entomopathogenic nematodes are available now for use versus white grubs in turf. Formulations of oriental beetle pheromone are being developed for mating disruption. Further research is needed on milky disease strains in order to maximize their use in white grub control. Bacillus thuringiensis japonensis strain Buibui is very effective for control of oriental and Japanese beetles and a commercial product will hopefully be available within the next few years. The addition of Btj to the control arsenal will add a curative control product of which few exist at the present time.
Thank you for your support.
Sincerely,
Dr. Steven R. Alm,
Dept. of Plant Sciences
9 E. Alumni Ave., Suite 7
University of Rhode Island
Kingston, RI 02881
