Research Projects
Japanese beetle adult
Cultivated row middle
Sweep sampling in buckwheat planted in row middles
Blueberry color sorter in action
Japanese Beetle Research in Highbush Blueberries
Zsofia Szendrei and Rufus Isaacs
Introduction
Michigan leads the nation in production of highbush blueberry, with over 40% of the US crop. However, the financial security of the Michigan blueberry industry is threatened by the recent invasion of the Japanese beetle (Popillia japonica Newman, Coleoptera: Scarabaeidae) into its major production centers. The zero threshold (zero insects in any of the packages of blueberries) for rejection of blueberries by processors or the fresh export market demands superlative pest control by the grower. However, chemical control of adults is challenging at farms with high Japanese beetle pressure. This one-dimensional approach may also pose some environmental risks, due to the persistence and toxicity of some insecticides to non-target organisms.
Suppressive environment for beetles
A suite of approaches is required to provide options that can be integrated into farming for reducing the likelihood of beetle infestation and contamination. By using a multi-tactic approach, we aim to provide the blueberry industry with multiple lines of defense to create a suppressive environment for Japanese beetle. Row-middle cultivation in fields and the planting of cover crops have the potential to provide sustainable approaches to creating a non-preferred habitat for this pest. These cultural controls could disrupt the life cycle by reducing the likelihood of beetle egg laying in blueberry fields and by reducing survival of grubs feeding on non-preferred hosts.
Cultivation and grub density
In 2001 and 2002, we surveyed Japanese beetle grub abundance at fifteen commercial highbush blueberry fields, and found that fields with cultivated soil between rows of blueberry bushes had 72% lower larval density of P. japonica than fields with grass between bushes. Samples taken in the uncultivated field perimeters indicated that cultivation inside fields reduces Japanese beetle larval populations in perimeters. In a replicated field study, grassy plots established between rows of blueberry bushes that were cultivated in spring and kept bare all year had lower abundance of Japanese beetle grubs than plots that retained perennial ryegrass. The effect of rotovation timing on grub abundance was not consistent, but most timings caused similar reduction in P. japonica larval density in the row middles. Cultivation in the spring and in the autumn caused 50.5% and 68.8% reduction of larval density in the two years of the study. These results indicate that cultivation can reduce the likelihood of P. japonica becoming established in fields, and that cultivation should be integrated into programs to control this pest, particularly in perennial fruit production systems.
Cover crops for beetle suppression
Our research is currently focusing on the effect of cover crops on female egg laying and larval development. Ground covers are grown in the row middles of many perennial agricultural systems to improve production, lower pest densities and attract beneficial insects. Cover crops are already used in some blueberry farms in Michigan to increase soil fertility, suppress weeds, prevent soil erosion, conserve soil moisture, and reduce the need for herbicides. Results from our previous studies in small plots have shown that manipulation of female JB behavior by ground covers can lead to reduced abundance of grubs. These results are promising, because they show potential to use cover crops in pest management in agricultural fields.
Chemical control
Many agricultural production systems affected by Japanese beetles employ insecticides to control either the larvae while in the soil, or the adult beetles on the plants during the summer. Our research focus is on small fruit crops, and research is underway in strawberry, blueberry, and grape to evaluate currently-registered and new alternatives for control of this pest. Results of this research are published in Arthropod Management Tests, in peer-reviewed journals, and are presented to grower groups during meetings organized by MSU Extension and other groups. The overall experience with different beetle control products registered for use in fruit crops is reflected in the annually-updated Michigan Fruit Pest Management Guide, MSU Extension publication E-154. This is available for purchase or it is available online in PDF format.
Post-harvest removal
There are many different models and manufacturers of color sorters that may be able to remove insect contaminants from fruit. These range from relatively simple machines that are designed to remove off-colored berries, but which also pick out some beetles. More sophisticated (and expensive) machines can be tuned to detect the wavelengths of light reflected by beetles, and can eject the beetle out of the stream of berries as it moves through the processing line. These machines are an improvement over the generic color sorters. You get what you pay for.
Summary
If fruit growers are faced with the threat of Japanese beetle infestation, they should consider all the management options available to them, so that the greatest degree of control can be exerted on this pest. At commercial fruit farms where Japanese beetle contamination is a potential problem, because the fruit must be completely free of beetles, growers should consider integrating cultural controls, soil applied chemicals for grub control, foliar insecticides for adult beetle control, and post harvest removal. This combination of tactics will work better than any one tactic alone.
For more information on Japanese beetle:
1.Japanese beetle factsheet (for blueberry growers) PDF copy (requires Adobe Reader www.adobe.com.)
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