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Pests
| Pest Prevention |
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Cleanliness is key to insect prevention and control. A clean totally enclosed environment can be easily controlled. Keep the floor, walls, tools, and containers clean and free of any debris.
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| Control |
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Prevention and cleanliness are the bast control there is. Even with the best houeskeeping, sometimes pests can get into your garden and begin to take hold. Attacking the weakest plant first, they can launch a all out assault on your garden in a matter of days.
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| Sprays |
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Sprays will often kill the adult bug only. Larve and eggs have to be handled in a different way.
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| Biological control |
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Predatory bugs
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| Spider Mites |
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The eight-legged adult can be pale green, greenish amber, or yellowish. Usually having two (sometimes four) black spots on top, the twospotted spider mite is about 0.4 millimeters long.
Eggs: The spherical egg ranges from transparent and colorless to opaque straw yellow.
Larvae: The six-legged larva is colorless, pale green, or yellow.
Nymphs: Similar to the adult except in size, the nymph has eight legs and is pale green to brownish green. Large black spots may develop on each side. BIOLOGY Host Plants: Twospotted spider mites have been reported on over 300 host plants, that include over 100 cultivated species. Violets, chickweed, pokeweed, wild mustard, henbit, vetch, and blackberry are common foci from which infestations develop on nearby crops.
Damage: Twospotted spider mites pierce the epidermis of the host plant leaf with their sharp, slender mouthparts. When they extract the sap, the mesophyll tissue of the leaf collapses in the area of the puncture. Soon a chlorotic spot forms at each feeding site. After a heavy attack, an entire plant may become yellowed, bronzed, or killed completely. The mites may completely web over entire plants.
Life Cycle: Twospotted spider mites are important pests on more crops than any other arthropod in the Southeast. Though insects and mites are in a group called the Arthropoda (meaning jointed foot) because jointed legs are common to both, spider mites are not actually insects. They are more closely related to spiders, and they derive their name from the thin web which some species spin.
In North Carolina, twospotted spider mites overwinter as adults in the soil or on weed hosts such as violets, henbit, and hollyhocks. In mild winter weather, twospotted spider mites continue to feed and lay eggs, although development in the winter is much slower than in the summer. From the eggs hatch six-legged larvae. They develop into eight-legged nymphs which pass through two nymphal stages. After each larval and nymphal stage, there is a resting stage. The adults mate soon after emerging from the last resting stage, and in warm weather the females soon lay eggs. Each female may lay over 100 eggs in her life and up to 19 eggs per day. Development is rapid in hot, dry weather. Each generation may take as many as 20 or as few as 5 days to mature.
They often damage one species of plant quite heavily and then disperse to other hosts. When a plant is heavily damaged, the mites migrate to the outer periphery of the plant. From here, even the gentlest of breezes can carry them a significant distance to attack new hosts.
MANAGEMENT STRATEGIES Cultural control: If spider mite infestations are detected early enough, a daily misting or spraying with water can be an effective control.
Pesticides: The use of foliar insecticides in hot, dry weather can induce spider mite outbreaks by killing the beneficial arthropods that would normally feed on the mites. In addition, a fungal pathogen attacks spider mites following short periods of cool, damp weather. Certain fungicides can eliminate this fungus and should be avoided for several weeks if plants are infested and such conditions occur.
The resting stages and eggs of the twospotted spider mite are more tolerant to pesticides than the motile forms. Consequently, a second application of pesticide may be necessary at 4- or 5-day intervals in hot weather (7 to 10 days in cool weather) to kill those mites that may have survived the first application. For specific chemical control recommendations, consult the Cooperative Extension Service.
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| Aphids |
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Adults: The winged adults are about 2 to 2.5 millimeters long; soft bodied; and dark, shining mahogany brown. Due to their dark color they were once called "blackflies." Wingless adults are only 1.5 millimeters long. Small, black, sturdy cornicles are found on the end of the body.
Nymphs: Nymphs resemble smaller versions of the adult aphids (0.6 to 1 millimeters). Nymphs have a dull, brick-red bodies with relatively long legs and antennae. The cornicles are short and dark. The outer two-thirds of the legs and antennae are gray (young nymphs) to dark gray. Older nymphs have proportionally longer cornicles. Those destined to be winged adults have wing buds in the later instars.
BIOLOGY Host Plants: Chrysanthemum is the only known host for this aphid in North America, but it has been reported on a few related plants in Asia.
Damage: The chrysanthemum aphid feeds by piercing the plant surface with its threadlike mouthparts to suck out plant juices. They gather about the terminal buds and feed on the new growth. This feeding causes distorted growth and the leaves may be covered by the feeding aphids' honeydew and cast skins. Sooty mold may grow on the honeydew giving the leaves and stems a black appearance. Chrysanthemum aphids are able to transmit chrysanthemum vein mottle virus and chrysanthemum virus B.
Life Cycle: Only female chrysanthemum aphids are known. They reproduce by giving live birth to more females, without mating. Chrysanthemum aphids overwinter in greenhouses where they feed throughout the winter. During the warmer months they leave the greenhouses in search of new plants. They also may be moved about as plants are shipped or sold. When the winged female stage infests new plants, it usually starts feeding and producing live nymphs. Each female can produce four to eight young aphids per day.
Within about a week the new nymphs mature into wingless females which begin to bear young of their own. One aphid on a plant in a short time may build the population up to hundreds of individuals . As the plant becomes crowded, more and more of the offspring develop into winged females which in turn migrate to other plants to begin new infestations.
MANAGEMENT STRATEGIES Infested plants in the greenhouse should be sprayed thoroughly when aphids are first noticed. On outdoor plantings, natural enemies may control minor infestations.
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| Leafminers |
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Insect larvae that live within leaf tissue. Many cause damage to garden plants and crops. Any of various small moths or dipterous flies whose larvae burrow into and feed on leaf tissue, especially of the family Gracilariidae.
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| Fungas Gnats |
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The flies are slender with comparatively long legs and antennae. They are grayish-black and about 2.5 millimeters long.
Eggs: The yellowish-white tiny eggs are 0.2 millimeter long and 0.1 millimeter wide.
Larvae: Darkwinged fungus gnat maggots have shiny black head capsules and white bodies. The last body segment is lobed and helps push the insect along. Mature larvae are about 5.5 millimeters long.
Pupae: Initially white, pupae become dark shortly before the adult emerges. BIOLOGY Host Plants: Darkwinged fungus gnat maggots feed on the roots of alfalfa, carnations, clover, corn, cucumbers, Easter lilies, geraniums, lettuce, nasturtium, peppers, rape, poinsettias, potatoes, soybeans, wheat, and organic matter.
Damage: Damage first becomes apparent when plants lose their healthy appearance and wilt. Darkwinged fungus gnat adults are usually noticed before injury caused by the maggots is apparent.
Life Cycle: Darkwinged fungus gnat maggots have only recently been recognized as important pests in greenhouses and mushroom cellars. They are also pests of house plants. Several of these flies are of economic concern. Generally, darkwinged fungus gnats are most abundant in greenhouses in the winter and spring. Adults and larvae inhabit moist, shady areas. Adults live about 1week, during which time each female deposits 100 to 150 eggs. They are laid in strings of 3 to 40 in the top of the soil, usually near stems of plants. They hatch within 4 days in the greenhouse. There is a tendency for the progeny of each female to be all one sex.
The larvae begin feeding on the root hairs and roots usually in the upper centimeter of medium, working their way up the plant and into the stem; however, they also feed on any organic matter in the soil. Being somewhat gregarious, the larvae often form clusters in the soil. They mature in about 14 days, after which they construct a pupal case, made of silk and debris, in the soil. The pupal stage lasts about 3.5 days. Adults are weak fliers, but they run rapidly on the soil surface or may remain motionless.
MANAGEMENT STRATEGIES Cultural Controls: Clean cultural practices and lack of excessive watering usually will prevent fungus gnat infestations. Since fungus gnats prefer potting mixes containing peat moss and abundant moisture, consider using bark mixes and avoid overwatering ornamental plants. Decoy pots of sprouting grain are attractive to females, that lay eggs in these pots. Afterwards, the pots should be submerged in boiling water or the contents destroyed in some manner every 2 weeks to destroy the eggs and maggots.
Biological Control: Fungus gnats have few efficient natural enemies. The parasitic nematode, Steinernema feltiae, has reduced fungus gnats in mushroom houses 85 percent when applied at a rate of 600 per square meter. Another nematode, Steinernema carpocapsae, is now on the market for fungus gnat control in greenhouses.
Pesticides: Some species of fungus gnats in mushroom houses have developed up to 47-fold resistance to pyrethroid insecticides.
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| Mealybugs |
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The ground mealybug is white and 2.4 to 3.9 millimeters long. It resembles a springtail, but moves much more slowly and cannot jump. The ground mealybug has slender waxy filaments that form a sort of netting over some individuals. The ground mealybug also secretes a small amount of wax, which can give the soil a somewhat bluish appearance when the mealybugs are abundant. Pritchard's mealybug is snow white and 1.6 to 2.1 millimeters long and oval. It has small to non-existent eyes.
BIOLOGY Host Plants: The ground mealybug feeds on the roots of anemone, chrysanthemum, gladiolus, iris, and numerous other flowers, shrubs, and ornamental grasses. Pritchard's mealybug has become a serious pest of African violet, although it also infests Achillea, Arctostaphylos, Geum, and Polygala.
Damage: At times the ground mealybug becomes abundant enough to damage its host. Pritchard's mealybug causes devitalization, foliage deterioration, and even death of its host plant.
Life Cycle: Little has been published on the life history of root mealybugs. When infested African violets are irrigated, Pritchard's mealybugs crawl out of the drainage holes and spread throughout the greenhouse. Eggs are laid in a loose ovisac in clusters of at least six eggs. All stages can be found on the roots and potting mix of African violets where they resemble slow moving, snowy white collembola.
MANAGEMENT STRATEGIES
Pesticides: Pesticides applied as dips, drenches, or granules are more effective for root mealybug control than are foliar sprays. For specific chemical control recommendations, consult the Cooperative Extension Service.
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| Scales |
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Depending on the host plant, the adult scale may vary in size. The \scale varies from 4.5 millimeters on Cycas to as small as 2.0 millimeters on Asparagus fern. Relatively hemispherical, brown, smooth, and shiny, the scale may resemble a miniature army helmet. Young females may have a pattern of ridges in the form of the letter "H" on the dorsal surface.
Eggs: The oblong, pinkish beige eggs are about 0.7 millimeter long and are protected by the mother's body in a mass of hundreds.
Crawlers: The flat, pinkish beige crawler is about 1.0 millimeter long with two red eye spots. The antennae and legs are short and spindly. There are two setae protruding from the rear.
Nymphs: Nymphs are semitransparent, light yellow or pink, and flat (young) to humped (older). They are so closely attached to the host plant that the legs and antennae are concealed. Two pale lines start at the margin on each side and fade in intensity toward the middle. Nymphs and young adults may exhibit the characteristic "H" pattern of the black scale group.
BIOLOGY Host Plants: The hemispherical scale insect has a wide range of hosts including bamboo, camellia, chrysanthemum, crape myrtle, croton, ferns, figs, gardenia, honeysuckle, lily, orchids, and zamia.
Damage: The secretion of honeydew and subsequent formation of sooty mold detracts from the beauty and commercial value of the plant. Feeding causes the plant to become stunted and lose its leaves.
Life Cycle: The hemispherical scale insect is a tropical insect that has become a common greenhouse pest. In warmer temperate areas, the scale can live outside. Unlike many other scales, the hemispherical scale secretes little wax. However, the scales do produce much honeydew which allows sooty mold to grow. Males are unknown and reproduction is by parthenogenesis. Each female may deposit up to 1000 eggs. After laying the eggs, the female dies and her body shrinks to form a cup or helmet over the eggs.
Development for the egg stage and the three nymphal instars requires at least 40 days and may take as long as 105 days. There may be several generations each year in the greenhouse, with all stages being present at any one time. The nymphs do not move much once they have begun to feed. The hemispherical scale insect has a low rate of parasitism indoors, and it often becomes a serious pest.
MANAGEMENT STRATEGIES Biological Control: The most important parasite of hemispherical scale in the United States is Metaphycus helvolus Compere.
Pesticides: Hemispherical scale insects are relatively difficult to control because the eggs and young nymphs are protected by the body of the mother. For specific chemical control recommendations, consult the Cooperative Extension Service.
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| Thrips |
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Female banded greenhouse thrips, approximately 1.5 mm long, are primarily yellow at first but gradually darken to brown or black. The eyes are red; the narrow, fringed wings are gray brown with 3 white crossbands. Males are rare.
Eggs: When first deposited, the translucent elongate eggs are white 0.25 mm in length. Before hatching, each eggs wells and becomes dull white.
Larvae: The yellow or white larvae vary from 0.48 to 1.5 mm in length. They are wingless and have red eyes.
Pupae and Prepupae: These stages are white and found on the leaves. There are usually more individuals on the lower surface. BIOLOGY Distribution: Although sporadically distributed through out North America, banded greenhouse thrips are widely distributed throughout the world. They are particularly common in the British Isles, Europe, and East Africa.
Host Plants: In the greenhouse, banded greenhouse thrips attack many crops including cucumbers, begonias, cacti, date palm, bananas, callas, cestrum, amaryllis, aralia, chrysanthemum, dracaena, rubber tree, gardenia, croton, hydrangea, moon flower, schefflera, screw pine, tomato, and Mexican tea. In one experiment in Georgia, 44 species of plants were used as host plants out of 50 presented. The banded green house thrips showed definite preference for some species among those accepted as host plants.
Damage: Banded greenhouse thrips pierce plant tissues with their mouthparts and suck the juices. As a result, irregular white spots form on the leaf giving it an overall silver appearance. Eventually, these areas dry out and turn light brown. Some defoliation results.
Life Cycle: The banded greenhouse thrips, sometimes referred to as the sugar beet thrips, has gained notoriety as a major floricultural pest. In North Carolina, this thrips was first reported as a greenhouse pest in 1943 on white callas. In the greenhouse, thrips may breed continuously and have several generations per year. Eggs are deposited on the underside of leaves or along the stem. Approximately 2 weeks later, larvae emerge and begin feeding. Colonies of young larvae congregate on the underside of leaves and individuals are often covered with a watery globule of excrement. As the larvae feed, they develop through four instars, molting between each stage. The more mature larvae are typically found along leaf midribs or among dried-up foliage. After a larval stage of approximately 18 days, banded greenhouse thrips pupate. Adult thrips that emerge shortly thereafter are less voracious feeders than the larvae. Adults live 40 or more days and females may reproduce with or without mating. Males of this species are rarely found.
CONTROL: Banded greenhouse thrips are vulnerable to contact insecticides. Stored bulbs can be dusted with such an insecticide to prevent a thrips infestation on plants the following season.
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| Whiteflies |
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About 1.5 mm long, the adult is a white insect that resembles a tiny moth.
Eggs: The small oblong eggs, pale green to purple, are deposited on the lower leaf surface, often in a circle or a crescent.
Nymphs: The first instar nymph is mobile and similar to a scale insect crawler. Later nymphal stages are yellowish with red eyes, and are immobile. They resemble soft scale insects, but have an orifice on the back through which honeydew is expelled.
Pupae: The oval pupa is pale green to black when parasitized. The normal color, when empty, is clear-glassy with a fringe of glassy setae, and with some long glassy setae on the dorsal surface. The pupal case sits upon a vertical palisade of closely appressed wax rods (these are readily visible in side view).
BIOLOGY Distribution: Greenhouse whiteflies are worldwide pests of greenhouse-grown ornamentals and vegetables. First discovered in England in 1856, they were found in the northeastern United States in 1870. Tropical Central or South America are suggested origins of the greenhouse whitefly.
Host Plants: Greenhouse whiteflies infest a wide variety of ornamental and vegetable crops, and they can survive outdoors during the growing season, particularly in sheltered locations. Even trees may be infested (redbud, Kentucky coffee berry, and avocado).
Damage: Infested plants become chlorotic and unthrifty. Honeydew and sooty mold further detract from the appearance of the crop. Unless controlled, greenhouse whiteflies may completely destroy the commercial value of floricultural crop.
Life Cycle: Greenhouse whiteflies reproduce relatively slowly (one generation every 30 to 45 days), but each may lay up to 400 eggs and live as long as 2 months. Adults are usually found on the lower surface of new leaves. The new crawlers move about the plant for a day or two, often from leaf to leaf before inserting their mouthparts to feed. Once this occurs they probably do not move again until mature. The crawlers molt into nymphs and then into pupae. Finally, a new generation of whitish yellow adults emerges. They are soon covered by a white waxy bloom.
CONTROL Lower greenhouse temperatures used in the culture of some bedding and potted plant varieties tend to encourage infestations, because naturally occurring parasitic wasps (Encarsia formosa) are reproductively inhibited at temperatures below 24°C (75°F). The lady beetle Delphastus pusillus also attacks greenhouse whitefly.
Control of whiteflies is difficult because the eggs and immature forms are resistant to many aerosol and insecticide sprays. One must make regular applications of pesticides to control emerging adults until the last of a whole generation of immature whiteflies has emerged. However, some of the synthetic pyrethroid and synthetic insect growth-regulator pesticides are extremely effective and need not be applied as often.
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Fungas / Mold |
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| Diseases |
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| Algae |
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| Powdery Mildew |
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It is one of the easier diseases to spot, as its symptoms are quite distinctive. Infected plants display white powder-like spots on the leaves and stems. The lower leaves are the most affected, but the mildew can appear on any part of the plant that shows above the ground. As the disease progresses, the spots get larger and thicker as massive numbers of spores form, and the mildew spreads up and down the length of the plant.
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| Root Rot |
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Found in both indoor and outdoor plants where, as the name states, the roots of the plant rot. Usually, it is a result of overwatering. In houseplants, it is a very common problem, and is slightly less common in outdoor plants. In both indoor and outdoor plants, it is usually lethal. The excess water makes it very difficult for the roots to get air that they need, making them rot. To avoid root rot, it is best to only water plants when the soil becomes dry, and to put the plant in a well-drained pot. Using a heavy soil, such as one dug up from outdoors can also cause root rot.
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| Viruses |
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