Sap Feeding Insects
Sap feeding insects are generally very tiny and hard to detect before they begin to do damage. They get their food by piercing leaves or stems with sharp, needle-like mouth parts, and then sucking out the plant's juices. These attacks weaken plants. They tend to induce and spread plant diseases which often deforms the plant, causing leaves to curl, discoloration, and speckles. Some sap sucking insects include:
Aphids, also often called plant lice, are fairly tiny, usually green (but can be other colors including pink, yellow, and black), creatures that mass on plants. Aphids can be controlled by the introduction of wasps and other predators. Pathogenic fungi may also be effective.
Whiteflies are very tiny. Their nymphs form little white clumps on the undersides of leaves. They excrete sweet "honeydew" attracting ants, which may keep and maintain them, harvesting the sweet droppings. The adult whiteflies gather on the plants and can sometimes be found in small clouds hovering over the plants. Control of whiteflies using predator insects is only partially effective. In small gardens they can be washed off using insecticidal soap. Using dishwashing soap can sometimes harm the plant's leaves, especially if applied on a sunny day. Hummingbirds eat whiteflies. So having a hummingbird feeder in the garden can help control this and other garden pests.
Spider mites are related to the spider. They have eight legs and thus are not actual insects. They are so tiny that they are seldom noticed with the naked eye. Scorched and discolored leaves with tiny white speckled lesions are an indication that they might be present. They may be red, yellow, brown, or green. Natural control is accomplished mainly through lady beetles and other natural predators. Miticides that specifically target spider mites are available.
Leafhoppers are another sap feeding insect. These are not grasshoppers, but very small hopping bugs, usually 10-13 millimeters in length. They can be extremely harmful, attacking plants in mass, and also carrying plant pathogens. To control leafhoppers first practice good garden sanitation, leafhopper resistant varieties can be planted. Insecticides are also available for virulent infestations.
Sap sucking insects attack plants rather in the manner that mosquitoes attack animals. They suck out the life juices and often inject diseases at the same time. For the home gardener most attacks of this type can be dealt with by introducing beneficial insects or attracting hummingbirds or bats. Picking and destroying infested leaves and stems may also do some good. Spraying insecticidal soaps or insecticides is also an option. However, the gardener should remember that general insecticides can also kill beneficial insects, creating a vicious cycle of sap sucker attacks followed by sprayings made necessary by the lack of natural predators. The gardener should also always be on the lookout for plant varieties that are resistant to plant attacking insects that are prevalent in the growing region.
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