Japanese Beetle Control: Understanding Their Life Cycle

Japanese beetles are not much of a threat in their native country, Japan, since there is a natural predator. However, in many regions of the United States, without a natural predator, Japanese beetles have become the source of garden or orchard damage. Since they are a host on over 200 plants, Japanese beetles have become a significant threat to many people from commercial farmers and even to recreational “at-home” gardeners. However, what many people do not know is that the problem doesn’t lie with the Japanese beetle themselves, but actually the control methods that are used in efforts to get rid of them. Unfortunately, too many people are applying wrong amounts of insecticides or even the wrong insecticides altogether. Moreover, too little or too much of the insecticides are applied during the wrong seasons. By utilizing the right products and applying them correctly during the right time of year, you can potentially prevent a future Japanese beetle infestation in or around your garden.

Life Cycle of Japanese Beetles

There are 4 main developmental stages that the Japanese beetle goes through. Since control methods are going to be different for each stage of the beetle, it is crucial to know what stage of development is occurring during the season you are planning to apply your treatment method. The 4 stages of Japanese beetle development are the egg, larvae, pupae, and the adult.

The first batch of beetles will begin to emerge and they will then search for food to eat. Once they find the suitable plants to provide a sufficient amount of food, they will begin to feed immediately. All the while, they release pheromones to attract beetles that emerge later. Mating begins soon after and once mating is over, females will only feed on the plants for 2-3 days. After feeding for just a few days, they burrow into the soil to lay their eggs. Once they have laid their eggs, they return to mating and feeding. By the end of the season, they will have laid about 50 eggs in the soil.

The development of the eggs really depends on the temperature of the soil. If the moisture in the soil is sufficient enough, the eggs are able to absorb the moisture and enlarge. As they enlarge, their initial oval shape becomes rounder and more spherical. Eggs develop the most rapidly in soils that are warm. Once the eggs have completely developed, the eggs will hatch and the larvae make their way up towards the surface. At the surface of the soil, the larvae begin feeding immediately on the roots of host plants as well as organic matter that is in the soil. The larvae, also known as grubs, continue to feed and as the soil becomes cooler, they begin to move back deeper into the soil. The grubs will spend the entire winter underground. When the soil starts to warm up during the beginning of the spring, they will once again, travel back up close to the surface, pupate, and then emerge from their cocoon as adult Japanese beetles.

Seasonal Cycle for Japanese Beetles

Japanese beetles emerge from their pupa stage during the summer. This primarily takes place during the months of June through July. As an adult, they feed, mate, and lay their eggs. Throughout the summer, female Japanese beetles will continue the cycle of feeding, mating, and laying eggs. Eggs that have been laid in the soil will hatch late in July and will develop through August. By late August, the Japanese beetle grubs will be fully developed. Since they hibernate during the winter season, grubs will begin to move deep into the soil during the end of August and into September. As the soil warms up in the spring, grubs will begin to move back up towards the surface of the soil in preparation to pupate.

Japanese Beetle Treatment

Many people will notice the most Japanese beetles in the summer and may notice grub infestations in the fall. Since adult Japanese beetles fly to their food, damage on the lawn or turf does not mean you have an adult infestation. Rather, it is going to be a grub infestation. Making sure that you are applying the correct pesticides during the right time of the year is extremely important.

Grub control can happen during two potential times of the year. Many people may apply insecticides on their lawn during the months of May until about mid-June. This is the time when grubs will resurface after a long overwintering period. However, since these grubs are fairly large and have had time to develop, it will be the best to apply insecticides before they go into their overwinter period. Around the months July and September is when grub treatment is the most effective. This is the time when they are about to make their way deeper into the soil to go into hibernation. The best type of insecticide to use to target grubs are correctly labeled granule insecticides that can be applied in a broadcast treatment around your lawn or turf.

Early in July and throughout the summer season, you will find the most adult Japanese beetles. The time period that the adults are around is little over a month. Although they may cause the most visible damage to your plants, using pesticides to contact kill Japanese beetles may also mean that you will potentially kill non-target insects or harm your plants. It is the best to hand pick them or use traps that are set away from your plants. Setting pheromone traps too close to your plants may simply attract them to the plants and you’ll find that you will have another infestation.

The worst time to apply insecticides is around the middle of June until early July. During this time, the larvae have already gone into their pupal stage and insecticides will virtually be ineffective. Waiting until they have emerged as adults or waiting for the eggs to hatch into their larvae stage in the late summer and early fall will be the best time to apply insecticides.

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Keep in mind that all insecticides are labeled. All product labels include a list of target pests and also directions of application as well as application or dilution rates. By federal law, it is require that you only apply insecticides as it is labeled. For more information on Japanese Beetle Control, call us at 1-800-788-4142 or e-mail us at info@pestmall.com.

Date: Saturday, 24. September 2011 16:58
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