Lawn Grubs

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Archive for August, 2011

Japanese Beetle


Japanese beetle is one of the largest insect threats for plants such as strawberries, pears, peaches, raspberries, grapes, tomatoes, peppers and of course our grass. Adult Japanese beetles feed on leaves, flowers, or fruits of more than 300 plant species. 


Larvae of Japanese beetles have short spines and white, long brown hairs. They live in lawns and grasslands and eat the roots of the grasses and plants they infest, which damages the ability of the plants to absorb nutrients and water. During larvae stage, Japanese beetles are susceptible to a fatal disease called milky spore disease, caused by the bacteria milky spore. 


Asparagus, citrus fruits, plums, raspberries, and corn are some of the common host plants for adult Japanese beetles. Other plants include turf grass, walnut trees, maple trees and sassafras. They are also fond of particular weeds and non-cultivated plants such as elder, bracken, Indian mallow, poison ivy, wild grape, and smartweed. 


Adult Japanese beetles feed on the upper surface of the plants by chewing the leaves between the veins, which gives the leaves a skeletonized appearance. Trees that have been ruthlessly damaged by Japanese beetles looks like they have been burned by fire. Adult beetles are highly active and travels fast; thus, they can easily infest new areas from a distance of several miles. However, they only make short flights when they feed or lay eggs. 



Picture by James Jordan

Controlling Japanese Beetles 

In Japan, this insect is not a serious plant pest as its natural enemies control its population. On the other hand, Japanese beetles came to the United States without their natural predators. Therefore, there is no check and balance and eventually, they became a serious plant pest. Japanese beetles also found an abundant food supply and favorable climate in the United States. 


Japanese beetle grubs are commonly controlled using preventive soil insecticides, but there are limited options to control adults and larvae. 


Natural Repellents – Using natural repellents, such as catnip, chives, garlic, and dead beetles’ remains have limited effectiveness. Other organisms like nematodes and predatory bacteria are also used to control Japanese beetles. Nematodes attack adult Japanese beetles and kill them from within. 


When existing in small numbers, Japanese beetles can be controlled spraying simple soap-water solution. Spray the solution to the plant, shake the plant in the morning, and dispose the fallen beetles or simply pick them off attractions. Do not leave any traces of Japanese beetle on the plant as it will only attract more insects. 


Pesticides – There are pesticides available that are highly toxic for Japanese beetles but they produce different results. Additionally, Japanese beetles are resistant to both poison and physical damage; hence, a lot of previously successful pesticides are no longer used lately. Similarly, spraying mixture of pesticide and water with garlic cloves and hot pepper can be sprayed all around the garden to kill Japanese beetles. 


Net – Putting a net over strawberry and blueberry bushes can likewise control Japanese beetle attack. Beetles are not smart enough to go into the net as long as it is wide enough to go up and over and back down the other side of the plant. 


Traps – For a swarm of Japanese beetles limited to a small area, the beetles can be physically removed from the plant by placing traps that lure and kill beetles. However, traps can be more destructive when not properly used. Moreover, these traps lure Japanese beetles so they can also result to more and bigger infestation. 


Summer is the time of the year when Japanese beetles damage trees and shrubs. They feed destructively on plants like roses, crape myrtles, hops, canna, grapes, and hydrangeas. Applying a systemic insecticide is prevented in the late winter or early spring to protect plants against Japanese beetles, but at the first signs of damage, spray insecticides are utilized. 



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