August 2008

Japanese Beetles!   They appeared in some neighborhoods in alarming numbers and proceeded to eat and eat and eat ... 

Due to the large numbers that congregate, these relatively small beetles can quickly damage and sometimes defoliate ornamental landscape plants.  Generally there are four main control strategies recommended to the homeowner:  Handpicking, pheromone traps, insecticide sprays to control adult beetles and grub control products that are applied to the soil in landscape beds and lawn areas. 

Often forgotten is plant selection ... another important control measure!  For example, Japanese beetles seldom attack red maples (Acer rubrum), but will feed on Japanese maple foliage.   

Trees that are most attractive to adults include: Norway maple, birch and pin oak, sycamore, purple leaf plums, elm and cherry trees, willows and lindens.  Other target foliage includes Virginia creeper, blackberries,grapes and crapemyrtles.  Field trials in Mississippi have shown 'Acoma', 'Pocomoke' and 'Pink Velour' crapemyrtles to be more resistant to damage than many other common cultivars. 

While most insect species only attack plant foliage, adult Japanese beetles eat both the flowers and foliage of plants such as roses, butterfly bushes, and cannas.  Apples, corn and the foliage of rhubarb is also at risk. 

Japanese beetles are strong fliers and migrate from nearby turfgrass, where the larvae developed, to feed. The Japanese beetle grubs can also damage landscape plants ... feeding on a wide variety of plant roots and turfgrasses.  
  
The following plant list is an excerpt from a Mississippi State University Extension Service bulletin.  Many landscape plants commonly found in southwest Missouri are found in both categories! 

RESISTANT TO DAMAGE BY JAPANESE BEETLES:
Red Maple & Sugar Maple
River Birch & Whitespire Birch
Eastern Redbud, Flowering Dogwood
Smoke Tree, Burning Bush, Hydrangeas
Ginkgo, Tulip Poplar
Japanese & American Holly
Saucer & Sweetbay Magnolia
Norway Spruce, Canadian Hemlock & Yew

GENERALLY DAMAGED BY JAPANESE BEETLES:
Japanese Maple & Norway Maple
Crapemyrtle & Althea (Rose of Sharon)
London Planetree 
Sandcherry & Purpleleaf Plum
Weeping Willow & Pussy Willow
Chinese Wisteria

Excepts from: Mississippi State University Extension Service 'Guide to Selecting Landscape and Garden Plants Based on Susceptibility to Adult Japanese Beetles'