Big Year for Japanese Beetle

Japanese beetle (Figure 1)  is having a big year in 2017, likely due to late summer rains and a mild winter in 2016-2017. It is attacking foliage and ripening fruit in many parts of the state. Grapes, blackberries, apples, beans, corn silks, hops, and okra are among its preferred fruits and vegetables. Green June beetle (Figure 2) is also beginning to become active and is often found feeding on fruits damaged by Japanese beetle. Green June beetle is a key pest on fruit as fruit softens and sugar content increases at harvest. These pests can create serious problems for growers when crops approach harvest due to some insecticide pre-harvest intervals. In some years, this is not a problem when populations are low, but this is not one of those years; numbers have been high in some areas.

Figure 1. Japanese beetle is a serious pest of foliage, as well as fruit at harvest. Their damage releases volatiles, which attract more Japanese and green June beetles (Photo: Ric Bessin, UK)

Figure 2. Green June beetle is a fruit feeder that can move in as the fruit begin to soften before harvest (Photo: Ric Bessin, UK).



PHIs and Harvest

There are a number of foliar options to control Japanese beetle before crops enter the harvest period. These include Sevin, pyrethroids (IRAC 3), and some neonicotinoids (IRAC 4A), dependent on crop labeling. However, during harvest, the options become more restricted because of pre-harvest intervals (PHIs) and harvest schedules. While many growers would like to use the insecticide that is most effective against these pests at harvest, they may not be able.

Pesticides used on food crops have required pre-harvest intervals (PHIs) that govern their use in the final few days before harvest. Some of the more effective products for Japanese beetle and green June beetle may have longer pre-harvest intervals (7 days or more) on some crops. In addition, prior to the start of the harvest period, when the more effective products can be applied (i.e., there is enough time to satisfy the pre-harvest interval requirement), green June beetle is not attacking fruit. So depending on the crop and availability of products, producers may need to balance maximizing insecticide effectiveness with minimizing disruption to harvest schedules.

Organic Alternatives

Neem sprays have been effective in repelling Japanese/green June beetle for a few days during the harvest period. But Neem needs to be reapplied every few day and can be expensive.

A newer product is Bacillus thuringiensis (Bt) galleriae, which is sold as beetleGONE and is a strain of Bt with the selective benefits of other Bt insecticides. Generally, Bt insecticides are of very low toxicity to pollinators and natural enemies of pests, making them compatible with IPM programs. What is unusual with beetleGONE is that it is labeled for both Japanese beetle adults and grubs. Other BT strains on the market are only effective against and labeled for immature stages, not adults. We have yet to evaluate the efficacy of this product.


Ric Bessin, Extension Entomologist





Posted in Fruit