By: Dr. Lakshmi Sridharan, http://www.lakshmi-sridharan.com/
Japanese Beetle is the most dreaded pest on roses in Midwestern and Eastern parts of the USA and Canada. The beetle’s unique life cycle, reproductive capacity, ability to colonize more than one host, and migrate from one country to the other crossing vast expanses of water helped the beetle to successfully colonize North America. Undetected by agriculture inspectors at Airports or Seaports, they move from country to country with travelers and their baggage. Being voracious feeders, the larvae (caterpillars, grubs) and the adult beetles cause heavy damage to plant parts and heavy financial losses to farmers, flower growers, and orchard owners.
Japanese Beetle poses a severe threat to roses and other members of the Family Rosaceae (apples, cherries, etc.). Adult Japanese Beetles infest hundreds of plant species that include shade and fruit trees, ornamental shrubs, small fruits, garden crops, weeds, and field crops. The grubs are serious pests of lawns and nursery stocks. (Photo of Japanese Beetles devouring rose leaves by Dr. Sridharan)
Japanese Beetle (Popillia japonica), a native of Japan, Korea and China probably first found its way from Asia to Europe and then into the USA through plant smuggling. The beetle arrived first in Southern New Jersey in 1916. The beetle population moved to Maine and other coastal states in the east, and westwards to a number of Midwestern States. Ferries transporting passengers between the coastal Maine and coastal Canadian Provinces helped in the onward migration and successful establishment of the beetle in Canada.
Favorable climatic conditions and gardening practices of homeowners helped the beetles to successfully establish themselves in North America. Almost every home in North America has a lawn. Adult females hide under the lawns and lay eggs. When eggs hatch, the hungry grubs feed on turf grass roots. Roses and fruit trees provide food for adult beetles.
Japanese Beetle (Popillia japonica (Newman)) is a member of insect Family Scarabaeidae, and the order, Coleoptera. The ovoid adult beetles, both male and female are beautiful with a shiny metallic green body and coppery brown fore wings. A row of 5 lateral brushes of white hairs on each side of the lower surface of the last abdominal segment distinguishes the Japanese beetle from the rest of beetle family.
Metamorphosis is characteristic of all insects’ life cycle. During its life cycle, the beetle passes through four developmental stages — egg, larva (grub), pupa and adult. Each stage has its own characteristic morphological, and anatomical features very different from the succeeding stage. The beetle does extensive damages to plant life as a grub and as an adult. During the pupal stage, it may appear to be sleeping; however it undergoes dramatic changes invisible to the naked eyes of a gardener to emerge later as a fully developed beetle. Fortunately for the roses, the beetle has only one generation per year.
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