About Japanese Beetles
Japanese beetle is a native pest to the main island of Japan and can now be found throughout North America. Japanese beetles are active on warm sunny days throughout the summer months from about June to August. You are able to tell if there is a Japanese beetle infestation on your property by the skeletonizing of outdoor plants and more specifically their leaves. Adult Japanese beetles can also be seen flying around your property.
Japanese Beetle Reproduction and Life cycle
Fully mature Japanese beetles live a short life of 30 to 45 days on average. When temperatures reach 21°C, beetles begin flying aimlessly from plant to plant due to the response of chemical stimuli and sex pheromones. They will dig themselves out of the soil and start to search for food and mate in late June and early July. Sometime during July, female beetles will spend 2 to 3 weeks laying up to 60 eggs in the ground. During mating time females feed, mate and lay eggs, repeating this process every 1 to 2 days. Each time they produce eggs female beetles have about 5 eggs at about 2 to 4 inches deep in the soil. They produce C-shaped larvae which are a milk white colour with a brown head and three pairs of legs. Prior to this short adult life, larvae or grubs will go through winter in a dormant state underground. In the spring, the larva emerges and by summer is a fully mature, reproducing adult.
Japanese Beetles Identification and Habitat
Fully mature Japanese beetles have shiny metallic green bodies with copper colored wings and little white tufts on the rear of their stomach and along their sides. They are oval in shape, about 10mm long and 6mm wide.
Japanese beetles will eat many plants. That being said, adults prefer apricot, blackberries, blueberries, cherry, corn, clover, early apples, elm, asparagus, grape vines, linden, maple, peach, plum, raspberry, roses, soybeans, woody ornamentals and zinnias. They are extremely attracted to grape vines and can be found in large numbers on them which can create a large amount of defoliation. For the most part, adult beetles eat the upper surface of the foliage chewing on the tissue between the veins - also known as the skeleton of the leaves, leaving a lace-like skeleton behind. From 7 to 10 days after the Japanese beetle emerges, they stay on the lower growing plants. As they grow and develop into fully mature adults, the height of a plant no longer matters. Japanese beetles prefer to eat leaves that are directly exposed to the sun, starting at the top and working their way down the plant. When the leaves on the plants become less attractive, Japanese beetles move onto flowers and crop fields, such as clover and corn. They will eat large areas on plants that have thin leaves and some flowers. Japanese beetles have occasionally been seen eating small areas of plants with thick, tough foliage on the upper surface of these plants. Once the leaves have been injured, they turn brown and fall off. As for the larvae, they feed on the roots of many plants but prefer and severely attack turf.
Japanese Beetles Control Methods
Control of Larvae
If there are adults feeding in one area, it does not mean there is a larvae infestation in the turf. It is important that you make sure there is a large infestation before applying any insecticides to eradicate the larvae. If there are parts of your grass that have turned brown, it most likely means there is an infestation of larvae below it. For optimal control of larvae, apply the insecticide from mid-July until the end of September, depending on the insecticide. Be sure to carefully read the label for cautions and proper application. Here are three insecticides that can be used to eradicate Japanese beetle larvae: Imidacloprid, Halofenzide and Trichlorfon. Imidacloprid when used has minimal risk to other fish and mammals and is best applied from July to early September. Halofenzide applied when fully mature adult females are laying eggs (July to the end of August) is most effective in abolishing Japanese beetle larvae. Trichlorfon is a fast-acting insecticide that degrades quite fast in high pH soil and in very hard or alkaline water. The best time to use this particular insecticide is in a rescue treatment when there is damage to your turf in late summer. After applying insecticides it is important to irrigate the sprayed area to increase the insect control. That being said, a large rainfall or irrigation soon after the application can reduce the concentration of the insecticides. After insecticides have been sprayed, areas should be checked 7 days after, this is especially important if the areas are very heavily infested with larvae. 10 days after the chemicals have been applied and larvae are still alive, apply a different product of insecticide.
Control of Adults
If you are dealing with a small infestation in a particular area, picking Japanese beetles by hand is manageable. The presence of a few beetles on a particular plant will attract even more to come to the plant as well. It is very important that you do not let beetles accumulate; Japanese beetles will be less likely to move to a plant that have little to no beetles on them. An easy way to deal with a small infestation on small plants is to shake them off the plant into a jar that is filled with soapy water. When applying insecticides to fields, be sure they are registered for use on the crops you wish to spray. If you are spraying on food crops make sure to note the minimal number of days that must be had between the time of harvest and last application of insecticides. With all insecticide products, flowers and foliage need to be thoroughly treated and repeat spraying may need to be done to prevent reinfestation. Be sure to carefully read the label for cautions and proper application. It is extremely important to never spray when bees are foraging and avoid spraying on days that are windy. There are different chemicals used to eradicate adult Japanese beetles that feed on foliage. Foliar sprays of contact insecticides provide immediate knockdown control for mature Japanese beetles, such as acephate, carbaryl, pyrethrins and pyrethroids. Examples of pyrethroid products such as bifenthrin (TalstarOne, Onyx), cyfluthrin (Tempo, Garden Multi-Insect Killer and Bayer Advanced Lawn), deltamethrin (Deltagard), esfenvalerate (Ortho Bug-B-Gon Garden & Landscape Insect Killer), lambda cyhalothrin (Scimitar, Spectracide Triazicide), and permethrin (Spectracide Bug Stop Multi-Purpose Insect Control). Repeated application may be essential due to the fairly short residual effect the pesticides have. Chemical formulations with piponeryl butoxide (PBO) and pythetrins are very effective.
Latin / Alternative Japanese Beetle Names