Parasites are organisms that take advantage of other organisms so that they themselves can thrive. They do this by depriving their host organisms of vital nutrients and by feeding off of them. This is exactly what plant parasites do, unfortunately. And while many such parasites don't actually kill the plant they've infested, others can be very serious. These range from various sap-eating insects to different species of roundworms, beetles, tomato hornworms and many others.
Several different kinds of insects like to feed off the sap in plants. Usually, they'll attack the leaves of plants or trees because they're softer than bark and therefore easy to access. Different species of spider mites are common sap-eating parasites found on plants. If enough of them infest a plant, they can kill it by stealing away its sap. Due to their very small size, spider mites may only be noticeable by the telltale webbing they leave behind on the undersides of leaves.
There are a number of different roundworms, or nematodes, that are parasites of ornamental as well as vegetable plants. The sting nematode can attack tomatoes, onions and strawberries. It averages just over 1/10th of an inch in length and feeds off of a plant's root tips, eventually killing the root system. Plants suffering from an infestation often look very wilted and stunted. Tops of an infested plant can also appear damaged.
Beetles can be parasites of agricultural plants as well as trees. They can easily feed off of every part of a plant, including the leaves, stems, fruits, grain tops, bark and wood. Snout beetles particularly plague a wide range plant crops. Others,. such as the Japanese beetle, feed off of plant roots. Wood borer types, like bark beetles, can spread the microfungus responsible for Dutch Elm Disease. All have mandibles as well as typical beetle-like bodies.
Tomato hornworms are actually the caterpillar life stage of the five-spotted hawkmoth. They can be major parasitic pests in any garden, and they particularly love to eat the leaves and stems of tomato plants. They're often found feeding on potatoes, tobacco plants, eggplants and pepper plants. Very tiny at first, they eventually reach 3.5 to 4 inches in length within a month after birth. They're greenish-brown, have V-shaped markings and tiny "horns."
- University of Nebraska at Lincoln: Belonolaimus longicaudatus Sting Nematode
- North Carolina State University: "Coleoptera Beetles/Weevils"; John Meyer; March 8, 2005
- New England Complex Systems Institute: Parasitic Relationships
- The Garden Helper: How to Control the Insects, Bugs...Plants
- Cahri's Bugs Online: Tomato Horn Worms
- British Columbia Ministry of Agriculture: Dutch Elm Disease
- Photo Credit Hemera Technologies/Photos.com/Getty Images
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