Wednesday, June 18, 2014

Squash Bugs and Squash Vine Borers are Coming Out!

Now is the time in the vegetable garden when the eggs of pests like the squash bug and squash vine borer are seen, so take care to nip them in the bud! Here is some helpful bug data of how to manage them from the Clemson University Extension Office.
Squash Bug
Older squash bug nymphs (Anasa tristis).
Older squash bug nymphs (Anasa tristis).
Whitney Cranshaw, Colorado State University,

The squash bug (Anasa tristis) is one of the most common and troublesome pests in the home vegetable garden. Squash plants frequently are killed by this sap-feeding pest. Leaves of plants attacked by the bugs may wilt rapidly and become brittle. Winter varieties of squash, such as Hubbard and Marrows, are much more severely damaged by the squash bug than other varieties. Control is required to protect squash in the home garden.
The adult squash bug is rather large, brownish black, and flat-backed. It is about ⅝ inch (1.6 cm) long and approximately ⅓ as wide. The young, called nymphs, are whitish to greenish gray, with black legs. They vary in size from tiny, spider-like individuals when first hatched, to maturing nymphs, which are nearly as large as the winged adults.

Squash bug egg clusters (Anasa tristis).
Squash bug egg clusters (Anasa tristis).
Whitney Cranshaw, Colorado State University, 
Squash bugs overwinter in protected places as unmated adults. They appear rather slowly in the spring. They mate and begin laying egg clusters about the time vines begin to grow and spread. Eggs are yellowish brown to brick red in color and are laid in clusters of a dozen or more on the leaves. They hatch in about 10 days into nymphs that become adults in four to six weeks. Only one generation of bugs develops each year. New adults do not mate until the following spring.
The squash bug is secretive in its habits. Adults and nymphs may be found clustered about the crown of the plant, beneath damaged leaves, and under clods or any other protective ground cover. They scamper for cover when disturbed. The secretive nature of squash bugs can be used to your advantage in controlling these pests. Place a small, square piece of old shingle or heavy cardboard under each squash plant. As bugs congregate under it for protection, simply lift the trap and smash them with your hoe (or shoe). Other control methods include early planting and removing eggs and nymphs by hand.
Remove and destroy vines and discarded fruit after harvest to eliminate overwintering sites. Early detection of squash bugs is very important, as they are difficult to control and can cause considerable damage. Apply insecticides when nymphs are small, as adults are difficult to kill.
Squash Vine Borers
Squash vine borer larva (Melittia cucurbitae) and damage.
Squash vine borer larva (Melittia cucurbitae)
and damage. Alton N. Sparks, Jr.,
University of Georgia,
The squash vine borer (Melittia cucurbitae) ranges from Canada to Argentina and is the most serious enemy of squashes and gourds. It causes much trouble where only a few plants are grown in gardens. It rarely attacks cucumbers and melons. Great variations exist in the susceptibility of squash and pumpkin varieties. Butternut and Green-Striped Cushaw varieties are practically immune to attack, but Hubbard squash is highly susceptible.
The moths are day fliers and are often mistaken for wasps. Larvae are white, heavy-bodied and considerably over 1 inch (2.54 cm) long when fully grown.
The insect overwinters in the soil as a larva or pupa (a non-feeding stage where the larva changes to an adult) enclosed in a cocoon. Moths emerge in early summer and lay eggs on the stems of the plants, usually late May in the South. Upon hatching, larvae bore into vines and complete their development in four or more weeks. Then they leave the plant, crawl into the soil, spin a cocoon and transform to a pupa. There are two generations in South Carolina.
In a vegetable garden, various measures can be taken to control this pest. Till the soil in late winter to expose overwintering insects. Rotate squash to another location in the garden each season. Destroy vines that have been killed to break the life cycle. You can slit the infested vine lengthwise and remove borers or kill them with a long pin or needle. Place soil over slit stem after removing the borer to encourage root development, and keep plants well watered. Plant as early as the weather allows since borers do not emerge until early summer.

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