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Spring Insects – Whiteflies

At one time or another we have all seen these tiny snowflakes fluttering about a plant. A major infestation of whiteflies can look like a flying fog! They can seem to come out of nowhere and all of a sudden! They are small winged insects which look more like moths than flies and they multiply like crazy!

Whiteflies are not true flies. They are relatives of mealybugs, scales and aphids. Like these sucking insects, whiteflies attack the leaves, buds and stems sucking the juice out of them. Although considered more of a nuisance than anything else, large numbers of whiteflies can really stress plants. The leaves of infected plants may turn yellow,twisted or stunted, and wither and drop prematurely. This insect has a host range of more than 250 ornamental and vegetable plants.

As do their relatives, whiteflies secrete “honeydew” which lures other nuisance insects onto the host plant. Ants, wasps and beetles feed off the honeydew. And when the honeydew goes bad it grows Black Sooty mold. This mold damages the plants preventing them from processing food properly!

Whiteflies cannot overwinter in freezing temperatures outdoors in the north, but can thrive year round in the south and in greenhouses, hence the name of the most prevalent Greenhouse Whitefly! Many plants become infested in greenhouses and transfer the whitefly to other plants in the garden.

Prevention is the best management. Infestations typically originate from infested plant materials. Carefully check all new plants and quarantine them before moving them into a room with susceptible plants.

Insecticidal soaps work well with adult whiteflies. They are safe so you can spray any plant – including fruits and vegetables – without any hazard to people or pets that may be eating the harvest. Soap is certified for organic gardening so it’s an excellent choice for organic growers. These are contact killers for both insect and mite pests. They penetrate the body of the pest and result in rapid death. Keep in mind that white flies in all stages spend virtually all their time on the undersides of leaves. Make sure to cover the hard to reach spots when spraying.

Whiteflies have about a 30 day lifespan. They follow the life cycle of most insects – eggs to crawler to nymph to pupae to adult and they reproduce quickly. About four days from emerging from the pupae adults laying eggs. Insecticides are not effective against immature stages of whiteflies, applications need to be made every four days to kill adults before they begin to lay eggs for the next generation. Up to 7 applications may be needed to bring well-established infestations under control.

There are other insecticides available for whitefly control. Make sure to read the product label for use on crops and directions for preparing spray solutions.

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Spring Insects – Scale

Scale insects – so called because that’s what they look like. The young insects are small, soft-bodied and mobile. When the eggs hatch the young, six-legged scale insect “crawlers” disperse throughout the new tissue seeking suitable sites in which to feed. They attach themselves to the plant with long, threadlike mouthparts (stylets) which are six to eight times longer than the insect itself. Once attached, they lose their legs and antennae, and begin to secrete a waxy layer over themselves.

The immobile, “shell stage” of scales are adult females; males are small, fly-like and infrequently seen. Scale insects can be basically divided into two groups: soft scales and armored scales. Soft Scales generally secrete an attached, thin, waxy layer over themselves. The soft covering they secrete cannot be separated from the scale’s body. Soft scales typically move between branches and leaves during their lifecycle. Armored Scales shed skins and wax that is unattached to their body to form their hard, shell-like cover. These covers can be separated from the scale’s body. Hard scales typically do not move to leaves during their lifecycle. Most species of armored scales overwinter as eggs beneath the female cover. In spring, these eggs hatch into tiny mobile crawlers which migrate to new feeding sites.

Scale insects feed on plant sap slowly reducing plant vigor. They can occur on leaves, twigs, branches or trunks. Heavily infested plants grow poorly and may suffer dieback of twigs and branches. Their small size and general lack of mobility make them difficult to notice by the casual observer. Large colonies remove substantial quantities of plant fluids and cause wilting, but seldom kill their host.

As Scale insects feed on plant sap they secrete a sugar-rich sticky liquid called honeydew. Armored scales do not produce honeydew. This honeydew serves as food for ants and wasps and supports the growth of black sooty molds. It often falls on leaves or needles, branches, fruits or anything else immediately underneath the infested area of the plant. The sooty mold fungi grow on the honeydew.Sometimes plants not actually infested by insects may be affected if a tree above them is being attacked by a honeydew producing insect and the honeydew drops onto them.

Scale insects can be controlled by using dormant oil treatments generally applied in very early spring, before bud break. Summer oils can also be very effective but some plants are sensitive to these treatments. Check labels to make sure your plant is not harmed by the treatment you are considering. Many other insecticides, including insecticidal soaps, can be used only against the mobile crawler stage of scales since adult scales are protected from insecticides by a waxy covering. Natural enemies to scale include tiny parasitic wasps and predators such as ladybugs. It is very common for ladybugs to move onto a plant with a growing scale infestation; before deciding upon a treatment, look for adult and immature ladybugs on your plants.

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