Japanese Beetle Info For WI Corn And Soybean Growers

Jul 21, 2017

By Bryan Jensen

A number of questions and several sightings of Japanese beetles have occurred this past week. Emergence is well under way and damage has been evident in susceptible ornamentals as well as soybean. This summer’s flight seems to heavier than normal. Likely a result of the mild winter.

Japanese beetles complete one generation/year. Adults began emergence around the July 4th weekend and egg laying is probably underway. Immatures (grubs) are not a pest on field crops but will feed on the roots of turf and other ornamental plants. Larval survival is highest when soil moisture is adequate and winters are mild. Adults will feed and thrive through August before populations start to decline in September. Adult Japanese beetles are approximately ½ inch in length, have a metallic green thorax, bronze elytra (wing covers) and 6 white tufts of hair on each side of the abdomen below the elytra.

Japanese beetle adults: ½ inch in length, metallic green thorax and bronze elytra (wing covers), and 6 white tufts of hair on each side of the abdomen below the elytra.

Soybean

Adults tend to feed in groups making spot treatment possible. On soybean, they feed on the upper leaves and this damage is best described as “net-like” or “lacy” in appearance. The economic threshold for Japanese beetles and other defoliators on soybean is dependent on crop stage. Vegetative soybean can withstand a moderate amount of feeding (30%). The economic threshold on reproductive soybean is scaled back to 15%. Defoliation estimates should be made on a whole plant basis and is why many people tend to overestimate injury.

Thirty percent soybean leaf defoliation example.

Corn

In corn, Japanese beetles will feed on green corn silk that can result in poor ear fill. They rarely feed on leaves. Feeding damage is similar in appearance to corn rootworm adults and populations may be mixed. The established threshold for Japanese beetles is 3/plant (5-6/plant for rootworm adults) and silk clipping is within ½ inch of the ear tip. Presence of these numbers does not indicate an immediate need for treatment unless green silks are being clipped. If populations are mixed you will have to use your best judgement. However, once silks turn brown pollination is over and that field is no long susceptible to injury.

Source: wisc.edu

Video: A chain harrow is a game changer

Utilizing a rotational grazing method on our farmstead with our sheep helps to let the pasture/paddocks rest. We also just invested in a chain harrow to allow us to drag the paddocks our sheep just left to break up and spread their manure around, dethatch thicker grass areas, and to rough up bare dirt areas to all for a better seed to soil contact if we overseed that paddock. This was our first time really using the chain harrow besides initially testing it out. We are very impressed with the work it did and how and area that was majority dirt, could be roughed up before reseeding.

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