Leaf Eating Insects
Leaf eating insects can be highly destructive, one of the larger insects can defoliate an entire plant in a single evening. These creatures have chewing mouth parts that remove parts or all of leaves. Insects such as caterpillars, butterflies, moths, and grasshoppers in the main are leaf eaters. Snails and slugs, though not insects are considerable garden pests especially in damp areas such as the Pacific Northwest of the United States and British Columbia in Canada.
Some specifics about particular leaf-feeders:
Tomato Hornworms are the rather large larvae of the hawk moth. They are green and can be identified by the white or yellow chevrons they wear on their segments. They are voracious eaters. However, they seldom come in large numbers and are normally prey to wasps. They are fairly easy to spot and can be hand picked.
The Grasshopper is among the most notorious of leaf eating creatures, making its appearance as one of the ten plagues Moses brought upon Egypt to convince the pharaoh to let his people go. It also finds its way into western literature, Laura Ingalls Wilder writes about an attack of a swarm of grasshoppers in her book On the Banks of Plum Creek. Grasshoppers in ones and twos are not greatly destructive, but in masses they can strip whole fields bare.
Another leaf eater is the Parsley Worm which targets plants of the carrot family. This grows to become the black swallowtail butterfly. It seldom does massive harm to plants. Nevertheless it can usually be easily controlled by hand picking.
The cabbage worm grows to become the white butterfly. The worms generally attack plants of the cabbage family including brussel sprouts and broccoli. They are not usually very thorough, but they do cover a lot of territory. The cabbage worm is velvety-green and gets to be about an inch long (2-3 cm). In younger stages it attacks inside the leaves, in older stages, it eats right through the leaves. To prevent attacks on cabbages specifically, some organic gardeners recommend putting a nylon stocking over the head. Hand picking is also effective. Varieties such as red cabbage are resistant, and planting near aromatic herbs such as mint and rosemary will repel the insect.
Flea beetles are a small, black or brownish-black beetle with long hind legs that allow them to jump when disturbed. Flea beetles attack a wide variety of plants by chewing "shot-holes" in them. Mulching can help control the development of the beetle in its early stages by interfering with its early stages of growth which occur in the soil. Hand picking is difficult, vacuuming may be tried, but has only very short term benefits. Flea beetles are not as destructive as some other insects, they are most damaging to young plants. If the gardener can get healthy starts past the seedling stage, flea beetles will likely be a nuisance more than a destroyer of crops.
Leaf rollers are the larval stage of a variety of moths. They are usually dark green, brown, or black. They will roll up and make a cacoon of one or several leaves and then proceed to eat it. This actually protects them from pesticide applications that occur after the leaf has been rolled. They can be controlled by pinching the rolled leaves, which kills the caterpillars inside.
The asparagus beetle in both its larval and adult form attacks the asparagus plant. It lays its eggs on the stem. When eggs hatch the larvae devour the stem. Eventually the the larvae as well as the adults feast on the leaves of the plant. There are several natural controls, including hand picking, introducing lady beetles, and parasitic wasps. Always remove and discard old canes within which the beetle can over-winter.
Bagworms are the larval stage of clear-winged moths. They get to be about an inch long. The eggs are planted in a bag that is made from the leaves of plants. On pine or evergreen plants they can look like little pinecones. When the eggs hatch, the larvae form new bags as a place to pupate. To control, bags can be cut from the stem and disposed of by burning or other methods.
Webworms are the larval form of the tiger moth. In the fall they mass together in the leaves of trees, building large webbed enclosures around areas up to a one foot in diameter in the autumn. Although they generally do not destroy host trees, they are unsightly. The easiest way to deal with them is to cut off the branches they have infested and burn them. Alternately, open the nest with a stick so that birds may feast on the caterpillars inside.
Tentworms are the larval form of the lackey moth. Tentworms are often confused with webworms. However, the tentworm usually sets up its nests in the crotches of tree branches. It usually picks on fruit trees, but may also infest maples, oaks, ash and other trees. The worms actually leave the nests to feed, at which time they are susceptible to being eaten by birds and other predators.
Snails and Slugs though not actually insects can wreak havoc on garden plants. They are a problem mainly in damp climates. They can attack a variety of plants. They can vary in size from very tiny to several inches long. They leave a slime trail so they can often be tracked down and destroyed. They may also be trapped using stale beer in a bowl. Turning over loose boards or stones in a garden will often turn up slugs.
An application of Bt (Bacillus thuringiensis) a bacteria harmful to most caterpillars but not to pets and humans will take care of most of the insects in this category. Hand picking is also often an option. Try to avoid general pesticides as these can be harmful to beneficial insects. Always balance insect control with the desired garden yields, and always consider organic gardening pest-control options. Chemical sprays may be a final resort.
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