Thursday, August 2, 2012

Striped Cucumber Beetle

Does it look as though something has been chewing on the leaves of your cucumber, squash, melon or pumpkins? Are you finding girdled stems and scaring on the fruits? Perhaps you have even noticed that the plants appear smaller this season. If this sounds like your garden then chances are the Striped Cucumber Beetle has come to dine in your garden.

Meet The Pest:

Striped Cucumber Beetle Adult - Acalymma vittatum

Adult Striped Cucumber Beetles are yellowish in color, about 1/4 inch long, with three black stripes down the length of their abdomen. The thorax is yellowish with no striping while the head and antennae are dark in colour.

Plants at Risk
Cucumbers, squashes, melons, and pumpkins are the prefered food choices of the striped cucumber beetle but they will also feed on tomatoes and other garden crops if cucurbits are unavailable or there are more beetles than the available cucurbits can support.

Life Cycle
Adult beetles overwinter in plant debris and emerge in mid-spring, when temperatures reach about 18 degrees C. (right about the time cucurbit seedlings are beginning to emerge through the soil. Planting transplants rather than seeds may help give your plants a head start and get them past this vulnerable period). According to William F. Lyon and Alan Smith of the Ohio State University Extension Entomology the beetles will soon mate and the females will deposit 225-800 eggs in small clusters or singly into soil cracks at the base of cucurbit plants. This is said to occur about 8-25 days after mating, with the eggs hatching 5-8 days later. The larvae then spend about 15 days feeding on the roots and stems of fruit that is in contact with the soil. The time from egg to adult for the first generation of beetles requires about 1 month. Southern Ontario has only one generation per year.

Hand picking, crop rotation, row covers (remove during flowering period). Natural predators include: tachinid flies, soldier beetles and braconid wasps.

Cucumber Beetle Damage
Leaf Damage of Striped Cucumber Beetle

Leaves: The adult beetles chew holes in the leaves and can reduce them to tatters.

Stem Damage of Striped Cucumber Beetle

Stems: Larvae also feed on stems causing girdling.

Fruit Damage of Striped Cucumber Beetle

Fruit: Both larvae and adults feed on the fruits causing scaring.

Roots: The larvae feed on the roots which can stunt the growth of the plant. 
Cucumber Wilt Caused by the Cucumber Beetle
This cucumber plant will have to be distroyed. It has been infected with the Bacterium - Erwinia tracheiphila, causing what is referred to as Cucumber Wilt or Bacterial Wilt. The bacterium overwinters in the bodies of hibernating cucumber beetles who then introduce the bacteria into the plants through the fecal contamination of feeding wounds.The disease appears first as patches of discoloration, followed by a sudden wilting of the plant. The beetles are also known to spread squash mosaic virus. All cucurbits, except watermelon are potentially affected by the disease.

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