Lords Environmental - Imported Cabbageworm


Pieris rapae

The imported cabbageworm is the common velvety green caterpillar seen on the leaves of cabbage, cauliflower, broccoli and other crucifers. The caterpillars feed on the leaves when they are young; however, large larvae move about freely on the plant and eat out large irregular holes on the larger leaves and often penetrate the head of the cabbage.

The adult of the imported cabbageworm is a common white butterfly with black spots on the wings that may be seen flying about in the field from early spring to late fall. The eggs are deposited singly on the leaves of the host plant and are yellowish in color (cream colored). The larva is about 1 1/4 inches when full grown and is velvety green in color. The larvae attach themselves by a silken thread to the leaves of the host plant when they are ready to pupate. The pupa (or chrysalis) is a light green color.

The adult butterflies are present from early spring through late fall. They will begin depositing eggs singly on the undersides of the host (crucifer) plant leaves. The eggs hatch in about one week and the young larvae begin feeding on the undersides of the leaves. In about 10 days to 2 weeks the larvae become full grown and attach themselves to plant leaves by a silken thread then transform into the chrysalis (resting stage). In New York State there are three broods annually.
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Plagiodera versicolora

[Imported Willow Leaf Beetle]

The Imported Willow Leaf Beetle adults and larvae skeletonize the leaves of willows during the summer months. The beetles feed on both sides of the leaves eating the tissue between the veins. With a heavy infestation, all the leaves may turn brown. Trees with a heavy infestation may appear dead because of the brown skeletonized leaves.

The beetles are about 1/8 inch in length, stout with a metallic bluish-black coloration. The larvae are slug-like in form with a tapering abdomen, also bluish-black in color. Larvae are about 1/4 inch long when mature.

The beetles emerge from their overwintering quarters under bark of willows, or in piles of debris and leaf litter, and begin feeding on young willow foliage in late April. Feeding continues through the month of May. Beetles mate soon after feeding and the females lay yellow eggs in clusters on the undersides of the leaves. The young larvae emerge a few days later and begin feeding. Second generations begin in early June through July. In some years there may be a third generation. In late August or September the beetles again seek shelter under the bark or in piles of leaves where they will overwinter.
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Plodia interpunctella

[Indain Meal Moth]

The Indian meal moth is one of the more common moths infesting stored grain and grain products. Others may include the Mediterranean flour moth and the meal moth.

The larval stage causes the injury. Larvae feed on flour and meal products, dried fruits, nuts, bird food and dried pet foods. As the larva feeds it spins a web leaving behind a silken thread wherever it crawls. Small particles of food often adhere loosely to the thread making it conspicuous.

Many times an infestation is noticed when moths are seen flying around the home in the evening. They are attracted to lights and often appear in front of the television screen.

The Indian meal moth has a wing span of about 3/4 inch (18-20mm). The outer 2/3 of the wings are bronze to reddish brown, while the inner 1/3 is a grayish white. The larvae (caterpillars) are about 1/2 inch (12.5mm) long when mature. They are a dirty white color, sometimes exhibiting pink or green hues. The pupa (resting stage) is in a loose silken cocoon spun by the larvae and is a light brown color.

A female Indian meal moth can lay from 100 to 300 eggs during her lifetime. Eggs are laid singly or in groups on the food materials. Within a few days the tiny whitish caterpillars emerge. These larvae feed for a few weeks and when they are mature they often crawl up the walls to where wall and ceiling meet, or crawl to the top of the cupboard to spin the silken cocoon in which they pupate and from which the adult moth emerges. Mating occurs and the life cycle repeats itself. In warm weather the cycle may take only 6 to 8 weeks.

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[Insects and Firewood Facts]

With the increased interest in the use of wood as a home-heating fuel, many people are beginning to notice the insects that periodically emerge from firewood.

Do the insects cause any damage to the firewood? We do not feel there is any real damage associated with insects in firewood. If the seasoning (drying) operation is done properly, the wood will dry before the insects complete development, and they will not survive. Although one may observe small piles of sawdust on or near the woodpile which indicate insect activity, most of the wood used for fuel in the northeast are hardwoods, and little real damage occurs.

Will firewood insects attack wood in the house? For the most part insects are only nuisance pests in the house. However, if the house has the correct conditions for an insect infestation, firewood could be the source of damaging insects. One example might be carpenter ants. If one brings in wood infested with carpenter ants, and stores it in a basement or garage containing some wet structural wood, perhaps already starting to decay, carpenter ants might move into it as the logs dry out and establish a nest. This is the exceptional case, rather than the rule.

Should I spray logs to avoid insect pests? We do not recommend spraying firewood for any reason. Insect pests can be reduced by proper cutting and storage.

What insects attack firewood (or any type of wood)? There are three main groups of insects that can damage wood. They are bark beetles, ambrosia beetles and wood borers. The bark beetles burrow between the bark and sapwood, ambrosia beetles bore through the bark and into the sapwood and/or heartwood, while wood borers can be found either between the wood and bark, or in the heartwood or sapwood.

When are insects active? Most insect activity occurs during the growing season&emdash;in New York State from April to October. During this time adult beetles are actively looking for favorable woods on which to lay their eggs. From November to March insects hibernate, and few, if any, adults are present

Bark beetles and ambrosia beetles are active during the entire growing season and may have five or more generations during this time depending on the climate. With the wood borers, activities are more restricted&emdash;often to a certain few weeks of adult activity. In order to determine the periods of activity, you will have to know what types of wood you will be cutting and then learn the activity cycles of the various insect pests.

What can I do to avoid large numbers of insects? Cutting firewood at the right time of the year (during the dormant season) will help avoid some pests. Pile the logs soon after they are cut, either off the ground or under cover so that the inner bark dries rapidly and thoroughly before the beetles begin to fly in the spring. If logs are cut during the growing season, remove them from the forest as soon as possible. Even a few days exposure when insects are active may be enough time for an infestation to begin.

How should I store firewood? Firewood should be stored out-of-doors, under cover and near the house so that valuable space in the house is not used, but the wood is still nearby. Insects are kept outside this way and the dirt problem is reduced.

Store wood under cover to keep it dry&emdash;storage places might be a woodshed, unheated garage or utility building, or under a sheet of plastic or sheet-metal roofing. Be certain to keep an air space between the wood and any covering.

If wood is dried quickly, few insects are likely to survive. The greater the surface area of wood exposed to air, the more rapid the drying. Stacking wood in loose piles raised off the ground as well as splitting or sawing will accelerate drying. This is especially needed with logs greater than eight inches in diameter or longer than four feet.

Firewood placed in an open area will dry rapidly and deterioration will be prevented. Put a cover over the top tier of wood, clear plastic sheeting can be used. Temperatures under the plastic covering will rise higher than outside, warming the wood and evaporating the contained moisture. Water vapor either escapes or is condensed on the plastic; therefore, some arrangement for ventilation is necessary.
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Macronocutua onusta

[Iris Borer] The iris borer is the most serious pest of iris. It causes more damage than all the other insects that feed on iris.

The adult of the iris borer is a dull brown moth with a wingspan of about 1 1/2 inches. The eggs are laid on old leaves or debris in clusters of 25 to 30 and are at first a shiny white, later turning darker. The larval stage causes the damage&emdash;caterpillars (larvae) are pinkish with distinct brown heads. Newly hatched larvae are only about 1/8 inch long, but at maturity they reach 1 1/2 inches. The pupal stage is found in the soil near the plants, and is chestnut brown in color, and about 3/4 inch long.


  • In most instances the injury caused by the borer will be seen before the insects are observed.
  • Small pinholes in leaves, or young leaves notched or with ragged edges after blossoming in May and June.
  • A slimy watery appearance at the base of the plants and leaves during June and July.
  • Small piles of frass or "sawdust" around the base of the plants during July and August.
  • Hollowed out rhizomes in late July - August. Larvae may or may not be present

NOTE: Injury by the larvae provides infection sites for bacterial soft rot.

The egg stage is the one that overwinters. Eggs are deposited in late summer or early fall on the old leaves or on debris near the iris plants. The young larvae hatch in the spring from April to June. These larvae at first chew small pin holes in the leaves, and after several days may spend some time mining the leaves. Within a few weeks they work their way to the base of the leaf sheath and while in the sheath, feed on young developing leaves causing them to "bleed" or loose sap. This causes the plant to become slimy at the base and is sometimes mistaken for soft rot. From the sheath the larvae enter the rhizome and proceed to hollow it out, eventually reducing it to just a shell.

The center leaves of the plant may turn yellow and can easily be pulled out. The larvae continue tunneling in the rhizomes until they reach maturity. About mid-August larvae chew their way out of the hollow rhizomes and pupate in the soil. Pupae are often found 5-6 inches from the plant and about 5 inches below soil surface. After about a month, adults emerge.

Adults appear from mid-September through October. Mating occurs and females deposit eggs on the old leaves near the base of the plants. Each female may lay as many as 150-200 eggs. Eggs are deposited in clusters of 25-30. The adults are secretive, and prefer shaded habitats. Therefore infestations are usually heaviest in protected, thickly planted gardens.
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