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Spider Mites- How to eliminate them

Spider mites are a bane to indoor gardeners and knowing their life cycle is very useful in assisting you with eliminating them. Spider mites lay eggs when they are threatened with death. The best naturally occuring active ingredient to kill them is Pyrethrum (Pyrethrin) this active ingredient is extracted from the Chrysanthemum Flower and is the oldest natural insecticide known to man. Pyrethrin is a CONTACT kill product only ( must contact the pest to kill the pest) and has no residual activity-thus it is safe to use up to the day of harvest on all food crops.

The highest level of this active ingredient in the product that you chose to use is recommended. Insecticidal soaps which are recommended in a lot of articles and blogs are NOT EFFECTIVE-they contain the lowest amount of this active ingredient and contain high levels of soap which is very Phyto-toxic to your plants= they cause more damage than good.

Treating your plants with a very high quality pyrethrin based product will give you excellent results with the least amount of product used saving you time and money.

Spider Mites when treated with anything to kill them immediately lay eggs-this is there evolutionary defense. An indoor growing environment with high temperatures and humidity is the ideal environment for spider mites to procreate. In this environment they can go through a entire life cycle in 4-7 days. so to successfully eliminate them you must treat your plants every 3-4 days for 3 complete life cycles.

The best eradication method is to treat the underside of the foliage with a Plant Spray containing a high concentration of Pyrethrin .20% or higher. After treating the underside of the foliage it is time to Fumigate or Fog the growing area with a Total Release Bomb- Doktor Doom makes two excellent products for this application (Doktor Doom Botanic’s Insecticide Plant Spray-Canada, Doktor Doom Spider Mite Knockout Plant Spray -USA and Doktor Doom Total Release Foggers (Fumigators)- Canada or USA. repeat this application every 3-4 days for 3 cycles.

Additional growing area tips: Remove all dead foliage daily, do not allow pets or visitors into the growing area (spider mites are hitch hikers and can attach to all sorts of surfaces from the hair on your arm to the sleeve of your shirt) always use the same clothing for doing maintenance in your growing area and keep it laundered regularly in hot water and dried in a hot dryer. Be certain that the area that you are drawing fresh air from is either treated with Pyrethrin regularly or use very fine screens on your intake ventilation systems. Most infestations in indoor rooms occur near this source of fresh air! Cleanliness is very important- keep your growing area clean and free of debris daily.

Be certain that the source of your cuttings is a “Clean Source” to assist you with this treat your cuttings with the suggested Plant Spray from a distance of about 3-4 feet away-spray a mist in the air and allow it to land on all surfaces of your cuttings-do not soak the foliage- a light mist every 3-4 days is all that is required.

By following the above application and indoor growing area tips you should be well on your way to a spider mite free environment and produce excellent crops ready for consumption

Cuban Laurel Thrips

DESCRIPTION Adults: Cuban laurel thrips are large thrips (2.6 to 3.6 mm) that are dark yellowish brown to black.

Eggs: The eggs are cylindrical with rounded ends, smooth, and translucent white.

Larvae: The first stage larva is a tiny, translucent white insect. In top view the first stage larva is almost oval. Second stage larvae are also translucent white but are similar to the adult in size and shape. Both instars have red eyes. The abdominal segments taper from the thorax. In top view the second stage larvae are shaped like an elongate diamond. The posterior tube becomes dark in older larvae and is held pointing up.

Prepupae and Pupae: Prepupae are similar to second stage larvae except that the wing buds are externally visible. Pupae have longer wing buds and the antennae are folded back over the head. BIOLOGY Distribution: The Cuban laurel thrips is a pantropical species that occurs wherever Ficus retusa is planted. It has been recorded outdoors in California, Texas, Hawaii, and Florida.

Host Plants: Cuban laurel thrips feed on Indian laurel, weeping fig, India rubber plant, other figs, and various shrubs and herbs. In the floricultural industry, weeping fig is the host most often infested.

Damage: This pest feeds on the tender, pale green leaves causing sunken, reddish to purplish spots along the midrib. Immature thrips cause the leaves to curl inward or fold into a pocket in which the thrips continue to develop and in which they lay eggs. Heavily infested leaves eventually become tough and brown or yellow. They eventually drop from the plant prematurely. Infested trees will not be killed, but the ornamental value of the plant is reduced markedly. Like the flower thrips, the Cuban laurel thrips also bites people.

Life Cycle: Eggs are laid in great numbers inside the surface of the curled leaf. All stages of development can be found at any time within the pocket galls. Development from egg to egg-laying females takes about 30 days. Adult Cuban laurel thrips are active fliers and migrate rapidly during hot weather.

CONTROL Because the Cuban laurel thrips only attacks the tender, new foliage on small plants, it should be possible to prune out the new growth and eliminate the thrips population. Consequently there is no suitable foliage for feeding and oviposition and the infestation should die out before new growth emerges.

Two anthocorid bugs, Macrotracheliella laevis Champion and Cardiastethus rugicollis Champion, have been reported to be predators of the Cuban laurel thrips in Puerto Rico. Another anthocorid bug, Montandoniola moraguesi (Puton), was introduced from the Philippines in Hawaii to control this thrips. The insidious flower bug is a common predator of the Cuban laurel thrips in Florida.

Sweetpotato Whitefly

DESCRIPTION Adults: Adult sweetpotato whiteflies are small, approximately 1/25 inch in length, with a
pale yellow body and two pairs of white wings and covered with a white waxy powder. At rest, wings are
held in an inverted V position. Their compound eyes are red.

Eggs: Female whiteflies deposit pear-shaped eggs into the mesophyll or inner tissue of the leaf from the
lower surface. Eggs are attached to the leaf by a stalk-like process. Eggs are white when first laid, and
become brown prior to hatching. They are generally laid on the underside surface of the younger, upper
leaves of the plant.

Nymphs: The first nymphal stage is called crawlers and the last stage is often referred to as the pupa.
After hatching the crawlers move a short distance and settle to feed. Once settled, the subsequent three
nymphal stages are scale-like and sedentary. Nymphs are creamy white to light green and oval in outline.
The total nymphal period lasts about 2-4 weeks.

Pupae: The pupa or fourth nymphal instar will be somewhat darker beigeish-yellow and opaque and 0.6 to
0.8 mm long. Pupae are relatively more plump compared to previous nymphal stages. The apex of anterior
and caudal spiracular furrows have smalls amount of white wax deposits. The caudal setae are prominent,
and the caudal end is somewhat acute. Dorsal spines are present when the host leaf is hairy and absent
when the host leaf is smooth.

BIOLOGY Distribution: In addition to Hawaii, the sweetpotato whitefly has been reported as a serious
pest of cultivated crops in tropical and subtropical areas including Africa, Asia, Central America,
South America, and the West Indies where it is also known as the tobacco whitefly and cotton whitefly.
In North America, it has been reported from Arizona, California, District of Columbia, Florida, Georgia,
Maryland, Texas and Mexico (Cock, 1986).

Host Plants: The sweetpotato whitefly has an extremely wide host range. It attacks more than 500 species
of plants (Greathead, 1986) from 63 plant families (Mound and Halsey, 1978). In Hawaii, the sweetpotato
whitefly has been found on the following crop plants: annona (cherimoya, atemoya, sugarapple), avocado,
broccoli, cauliflower, Chinese cabbage, Chinese waxgourd, cucumber, Dendrobium (flowers), edible gourds,
eggplant, fig, green bean, guava, hibiscus, hyotan, lettuce, luffa, plumeria, poinsettia, pumpkin, rose,
soy bean, squash, sweetpotato, togan, tomato, ung-choi, watermelon, yardlong beans and zucchini. Although
not yet reported in the state, other crop hosts include cabbage, chrysanthemum, beans, bittermelon, dishrag
squash, pepper, pea, and radish (Mau & Tsuda). Weeds often serve as alternate hosts of crop pests.

Damage: Direct feeding damage is caused by the piercing and sucking sap from the foliage of plants. This
feeding causes weakening and early wilting of the plant and reduces the plant growth rate and yield
(Berlinger, 1986). It may also cause leaf chlorosis, leaf withering, premature dropping of leaves and plant
death. Infestations of sweetpotato whitefly nymphs are associated with the occurrence of irregular ripening
of tomatoes and silverleaf of squash. Indirect damage results by the accumulation of honeydew produced by
the whiteflies. This honeydew serves as a substrate for the growth of black sooty mold on leaves and fruit.
The mold reduces photosynthesis and lessens the market value of the plant or yields it unmarketable (Berlinger, 1986).

Damage is also caused when sweet potato whitefly vectors plant viruses. A small population of whiteflies is
sufficient to cause considerable damage (Cohen and Berlinger, 1986). Plant viruses transmitted by whiteflies
cause over 40 diseases of vegetable and fiber crops worldwide. Among the 1,100 recognized species of whiteflies
in the world, only three are recognized as vectors of plant viruses. The sweetpotato whitefly is considered
the most common and important whitefly vector of plant viruses worldwide. It is also the only known whitefly
vector of viruses categorized in the geminivirus group.

Life Cycle: Whiteflies have six life stages – the egg, four nymphal stages, and the adult. The development time
of this insect from egg to adult may range from 15-70 days dependent upon temperature and plant host. Development
occurs in temperatures ranging from 50 to 89.6°F (10 to 32°C). 80.6°F (27°C) appears to be the optimal temperature
for development. Under control conditions on cotton, the pest completes its development in 17 days at 86°F (30°C)
On the contentinal U.S. development from egg to adult under field conditions varies with the season; development
varies from 25 to 50 days.

Adults usually emerge from their pupal cases in the morning hours and may copulate a few hours later. Oviposition
occurs from 1 to 8 days after mating. Adult life span ranges from 6-55 days dependent on temperature. Females live
only 10-15 days under southern continental U.S. summer conditions, but can live several months during the winter.
In this species, reproduction can occur with or without copulation. Unmated females can reproduce by parthenogenesis
in which the females produce only male progeny. Females lay 80 to more than 300 eggs in their lifetime. The plant
host reportedly plays an important role in female fecundity.

CONTROL High reproductive rate and multiple host sequences provide optimal conditions for sweetpotato whitefly
population development. The varied habitats, seasonal population development and intra and inter-crop and wild host movement present an extremely complex and difficult challenge requiring new and innovative approached for formulating control and suppression methodology.

There is really no easy way of controlling the sweetpotato whitefly. Egg mortality is usually minimal. Weather and predation may cause high mortality rates during the crawler and first nymphal stages, but has only moderate effects on the later nymphal stages. In the past adults were easily killed with insecticides but pesticide resistance in sweetpotato whitefly populations is a common problem faced by many growers today. Sweetpotato whitefly has become resistant to chemical insecticides quite rapidly in other parts of the world, and the wisdom of relying only on chemical insecticides is questioned. Moreover, regular insecticide applications can result in resurgence of other pests.

We believe that a combination of cultural practices and chemical application would provide the best chance of controlling this pest. The use of sound cultural practices that may avoid, delay, or lessen the severity of the sweetpotato whitefly infestation is a good foundation to begin with. Careful selection of insecticides can help regulate sweetpotato whitefly populations to reduce losses not due to pathogenic organisms. Little can be done to reduce losses due to virus diseases, but we are fortunate that none have been introduced.

Fungus Gnats

DESCRIPTION Adults: 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.
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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.

Gladiolus Thrips

DESCRIPTION Adults: Gladiolus thrips emerge milky-white, but soon turn dark brown, except for the apical portions of the legs which are lighter. The wings, brown apically and lighter basally, appear to be darker with a grey band when folded over the back. This thrips is about 1.5 to 1.65 mm long. Males are smaller slightly smaller and lighter in color than the females.

Eggs: The eggs are opaque, white, kidney-shaped, and about 0.34 mm long and 0.2 mm in diameter.

Larvae: The larvae of the gladiolus thrips are light or pale yellow with red eyes and are about 1.0 mm long when fully developed.

Pupae and Prepupae: The pupae move only when disturbed and develop through 2 instars. The first instar (prepupa) has short wing pads and the antennae project forward. The second instar (pupa) has long wing pads and the antennae are folded back onto the head. Both stages are dark orange with red eyes and about 1.2 mm in length.BIOLOGY Distribution: Gladiolus thrips is now found wherever gladioli are grown. However, it cannot overwinter out-of-doors in northern Europe and northern North America.

Host Plants: The gladiolus thrips most seriously damages gladioli, but is also a pest of iris, carnation, lily, narcissus, freesia, amaryllis, tigerflower, poker plant, tomato, begonia, primula, snapdragon, chrysanthemum, and geranium.

Damage: Plants severely infested with gladiolus thrips have a spotted, bleached appearance (see Color Plate). Both leaves and petals are fed upon and appear withered. If flower buds are seriously damaged, the flowers fail to open. The entire plant may become stunted.

Life Cycle: Gladiolus thrips are believed to be an introduced pest from Africa, where gladioli are native. The thrips are brought into previously uninfested fields or greenhouses on infested corms. These rather sluggish thrips can overwinter at any stage on stored corms or on plants growing in greenhouses. Although the gladiolus thrips can maintain a population outside during the summer, they cannot overwinter outside in areas where the temperature consistently falls below 10° C.

These thrips have six stages in their life cycle: the egg, two larval instars, two pupal instars and the adult stage. Females deposit 100 to 200 eggs. Many times females greatly out-number the males in a population and parthenogenesis occurs. Parthenogenetic females produce eggs that develop into males. Temperature greatly determines the duration of each stage. During the warm growing season the development of the gladiolus thrips can occur in about 2 weeks. With such rapid development, the thrips can have nine or more generations outside during the growing season. The eggs are deposited in the leaves of gladioli or in the corms in storage. Larvae and pupae can be found in the buds or leaf sheaths, although the larvae often drop to the ground to transform into the quiescent pupae. Adult gladiolus thrips live 35 to 40 days.

Flower thrips

DESCRIPTION Adults: The flower thrips and the Florida flower thrips are exceedingly similar. They can be separated only by microscopic examination. Both are approximately I mm to 1.25 mm long and yellow, with brown blotching, especially about the middle of the thorax and abdomen. Males are smaller than females and are lighter in color.

Eggs: The flower thrips delicate egg is cylindrical, and slightly kidney-shaped, with a smooth pale or yellow surface.

Larvae: The immature thrips is lemon yellow, resembling the adult except for its lack of wings.

BIOLOGY Distribution: The Florida flower thrips has been found in Florida, Georgia, and Alabama and is likely distributed in other states of the southern United States. Evidently because of their small size, flower thrips are carried over large areas by frontal wind systems, the maximum rate of migration taking place in early week of June. Trapping records by sticky cards showed that these thrips are found in relatively equal numbers up to 135 feet (45 m). They have even been trapped at altitudes of 10,000 feet (3,100 m). The flower thrips has also been reported in western states. These thrips enter greenhouses through vents or doors, on plants brought into the house, or on people or supplies coming into the house.

Host Plants: Florida flower thrips have been reported from over one hundred species of plants. Roses and citrus are favorite hosts, particularly the white varieties. Most plants of the Rosaceae are infested. Flowers of a more or less open structure, where the stamens and pistils are easily accessible, are favorites. Flowers such as nightshade with stamens in a tube about the pistil are also favorites. Flower thrips have been collected from 29 plant orders including various berries, cotton, chrysanthemums, daisies, day lilies, field crops, forage crops, grass flowers, legumes, peonies, privet, roses, trees, truck crops, vines, and weeds. They seem to prefer grasses and yellow or light-colored blossoms. Roses are most susceptible in June.

Damage: Florida flower thrips always feeds on the most tender part of the plant, such as buds, flowers, or leaves. The effect of their numerous but shallow punctures is to give the injured tissue a shrunken appearance, and the damage is described as piercing and sucking fluids from the cells. The thrips feeds on the thick fleshy petals, pistils, and stamens of the flower, and then the affected parts turn brownish-yellow, blacken, shrivel up, and drop prematurely. Infested rose blossoms turn brown, and buds open only partially. The petals, distorted with brown edges, seem to stick together. Only the epidermis and relatively few mesophyll cells are affected. They also may feed on ovary or young fruit on some host plants. The numerous and shallow punctures on the surface cause characteristic markings that lower marketability dramatically.

Life Cycle: No published work has been done on the biology of the Florida Flower Thrips. The flower thrips was described in 1855 from Wisconsin. During warm periods, swarms of these tiny insects often fly in the afternoon. Flower thrips bite people, causing a noticeable stinging sensation. Their large numbers account for considerable and rapid damage to flowers, especially those with light-colored petals. Yet thrips contribute to pollination of some crops, an unexpected benefit! Flower thrips are generally found at the bases of the petals. They reproduce throughout the year in the warmer parts of the Southeast, with the majority of their 12 to 15 generations occurring in the warmer months. Newly emerged females begin to lay eggs within 1 to 4 days in summer and within 10 to 35 days in winter, reproduction being much faster in warmer weather. In summer, the adult stage is reached in about 11 days. Flower thrips pass through egg, two larval, prepupal, pupal, and adult stages. The eggs are inserted into flower or leaf tissue, and the prepupal and pupal stages are spent in the soil. In summer, flower thrips may live 26 days, though overwintering thrips may live all winter. Flower thrips can overwinter as far north as North Dakota in grass clumps and other sheltered refuges.

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. For specific insecticides and rates, consult the current Cooperative Extension Service publications on ornamental plant pests.

Green Peach Aphid

DESCRIPTION Adults: The small adult green peach aphid is light to dark green or pink, with red eyes. Three dark lines run down its back. Wings may or may not be present. The tobacco aphid is similar and can be either red or green.

Eggs: Found only in the northern United States, the egg is black and shiny for the green peach aphid. The tobacco aphid has not been found to have an egg stage.

Nymphs: The wingless nymph resembles the larger adult.BIOLOGY Host Plants: Green peach aphids have been collected from over 100 plants, including a wide variety of vegetable and ornamental crops. Spinach, potatoes, and peaches (the host on which eggs are laid) seem to be especially favored hosts. Tobacco aphids will be pests primarily on tobacco and closely related plants such as flowering tobacco and Nicotiana. It is probably not a major pest, but will feed on pepper and eggplant as well as cole crops such as turnips, kale, and collards.

Damage: Aphids suck plant sap and contaminate the host with honeydew and cast skins.
some hospitals refuse to allow cut flowers in patients’ rooms because of the mess by aphids. They are also the vectors of a number of plant viruses including tobacco, tomato, lettuce, dahlia, canna, and bee mosaics as well as tuber spindle, rugose mosaic, andleaf roll diseases of potato.

Life Cycle: In the northern United States, green peach aphids overwinter as eggs, but in the Southeast, no eggs are laid. Instead, female aphids give birth to young females during the growing season. The reproductive capacity of green peach aphids has been described as “fantastic.” High reproductive rates- and resistance to pesticides make the green peach aphid a formidable pest in the greenhouse. Up to 30 generations per year may take place in this pest’s southernmost range. The tobacco aphid probably overwinters on weed hosts or on cole crops that remain alive through the winter. Tobacco aphids are not known to have an egg stage, and they reproduce by giving birth to live young female aphids without mating. Their young are able to produce young as well without mating. If the plant becomes too crowded or if it becomes late in the season and the aphids need to find a winter host, the aphids give birth to young that will grow up to have wings and can move to other plants. Differences on reproductive rates exist between the red and green forms of the tobacco aphids. The red form is able to reproduce much faster during extremely hot weather than the green form.

On chrysanthemums, green peach aphids feed on all parts of the plant (melon aphids feed only on the buds and leaves, and chrysanthemum aphids feed only on the stems and leaves). Green peach aphids will not become established in the presence of the other two aphids unless pesticides are applied. In that case, green peach aphids outlive both melon aphids and chrysanthemum aphids.


MANAGEMENT STRATEGIES Because green peach aphids overwinter on weed hosts, infestations can occur in the greenhouse any time of year. Green peach aphids readily infest bedding plants and can be introduced into greenhouses whenever bedding plants are brought in from another grower. Although damage per aphid is often not serious, these aphids reproduce so rapidly that serious harm can be done in a short time.

Biological Control: Ladybugs, lacewings, syrphid flies, damsel bugs, wasps, and parasitic fungi tend to regulate green peach aphid populations outdoors.

Pesticides: These aphids’ resistance to pesticides calls -for thorough applications whenever a new infestation is found. Tobaccoaphids can be controlled in the same manner as green peach aphids.

Fern Scale

DESCRIPTION Adults: Female fern scale armor is oystershell or pear shaped, flat, light brown with the crawler cast skin a paler brown. Sometimes the second stage armor is also paler than the adult armor. They are 1.5 to 2.5 millimeters long. The male armor is white felted, three-ridged, and the crawler cast skin is beige to yellowish brown. Adult males are tiny, two-winged, gnat-like insects that are easily overlooked.

Eggs: Eggs of armored scales are usually oval and about 0.2 millimeter long. They are laid in groups under the female armor.

Crawlers: Fern scale crawlers are about 0.2 millimeter long, flat, and yellow with red eyes. The legs and antennae are well developed.

Nymphs: Female second-stage nymphs secrete an oval, pale brown armor about 0.8 millimeter long. Male second stage nymphs secrete a white armor which has three long ridges. Mature male second stage nymphs are about 1 millimeter long.

BIOLOGY Host Plants: Fern scales mainly infest true ferns (not asparagus ferns) and liriope. This pest has been recorded from numerous foliage plants, citrus, and other woody ornamental trees and shrubs in Florida.

Damage: Infested ferns are disfigured by the presence of male second stage armor which is conspicuous against the dark green foliage. Ferns in commercial production sometimes tolerate a tremendous scale population with little noticeable reduction in vigor or color. Feeding by female scales causes yellow spots on some fern varieties and on liriope. Males do not feed beyond the second stage of development.

Life Cycle: Little specific information is known about the biology of fern scales. Female scales lay their eggs under the armor. The female dies after the last egg is laid. Tiny crawlers hatch from the eggs and eventually emerge from under the mother’s armor. The crawlers move about until they begin to feed by inserting their long, thread-like mouthparts into the leaf and sucking out nutrients. The insect molts into a second stage which begins to secrete a waxy material from under the rear of the first stage (crawler) cast skin. Eventually these insects molt into the adult stage. Female scales begin to secrete the adult armor at the rear of the second stage armor. Males emerge from their second stage armor as tiny, gnat-like insects that crawl or fly to female scales to mate. The armor remains fastened to the plant long after the scale insect leaves (male) or dies inside (female). When populations become dense, females tend to lay male eggs so that heavily infested plants become conspicuously spotted by second stage male armor.

MANAGEMENT STRATEGIES Try to purchase plants from a supplier who does not have a fern scale infestation.

Pesticides: When fern scales are encountered, horticultural oils give adequate control without excessive phytotoxicity to ferns. Two thorough treatments 2 weeks apart should give good control. Ferns are notoriously sensitive to pesticides. Whenever treating ferns and other sensitive plants, treat at a time that the pesticide will be dry on the foliage before the plants are exposed to full sunlight. For specific chemical control recommendations, consult the Cooperative Extension Service.

Greenhouse Thrips

DESCRIPTION Adults: The head and central area of the body have a distinct network of lines. The body is dark brown with the posterior end much lighter; the legs are uniformly yellow; the wings are hyaline and narrow, but with a broad base; and the antennae are slender with a characteristic needle-like tip. The mature adults are about 1.3 to 1.8 mm long. The male is similar to the female thrips, but slightly smaller.

Eggs: The eggs are very small, banana-shaped, and white.

Larvae: The first larval instar is white; the second instar is yellow. Both instars have red eyes.

Pupae and Prepupae: The pupa and prepupa do not move about freely. These stages are yellowish with red eyes. Pupae are slightly larger, with longer wing pads, and antennae bent back over body. They become darker with age.

BIOLOGY Distribution: Although the greenhouse thrips is limited to tropical areas outside, it is found throughout the world in greenhouses. This thrips probably originated in Central and South America.

Host Plants: The greenhouse thrips has over 100 hosts, principally greenhouse and ornamental plants, but also a few crops and tropical plants. Some of the hosts are azalea, begonia, croton, cyclamen, ferns, fuchsia, grape vines, orchids, palm, and rose.

Damage: This thrips feeds almost entirely on the foliage, and large populations cause severe damage. Greenhouse thrips usually injure inner leaves and fruit. Damaged leaves appear silvery or bleached and, if the damage is severe enough, turn yellow and drop. Fruit that has been attached is brown, cracked, and has noticeable sunken areas. Dark spots of excrement are often noticeable on the leaves and fruit.

Life Cycle: Each female deposits 25 to 50 eggs in slits in the leaves. Under optimum conditions the time for development is 17 to 20 days for the eggs, about 13 days for the two larval instars, and about 5 days for the prepupal and pupal stages. The adults can live 7 weeks on plants growing in the greenhouse. All stages can be found throughout the year in greenhouses. Greenhouse thrips move relatively slowly and rarely fly. They prefer a cool, shady, and fairly moist atmosphere. These thrips feed in colonies on the foliage and fruit. They select neither the youngest nor the oldest leaves on which to feed. Often the fruit is preferred to the leaves. Since males are not common, reproduction is usually by parthenogenesis (laying unfertilized eggs). Males were first found in 1940.

Cyclamen Mite

DESCRIPTION Adults: These mites are tiny animals, less than 0.3 millimeter long. Colorless or brown tinted and waxy looking, they have four pairs of legs. The fourth pair of the female is slender with a long, hair extending from the tip. The fourth pair of legs of the males ends in a strong claw.

Eggs: The elliptical egg is 0.1 millimeter long and smooth.

Larvae: The young mites are about 0.2 millimeter long and are whitish and have three pairs of legs. The legs have microscopic claws and suction cups.

Quiescent Stage: This stage appears as an immobile, engorged larva. BIOLOGY Host Plants: African violets are most often damaged by cyclamen mites. They also have been found on ivy, snapdragon, chrysanthemum, larkspur, geranium, fuschia, begonia, petunia, daisy, and azalea.

Damage: Cyclamen mites cause tuberous begonia and cyclamen flowers to be discolored or to shrivel or wilt. Infested flowers may not open properly or may not open at all. The mites also cause puckering, crinkling, and curling of leaves; infested leaves become brittle. Infested cyclamen buds fail to open or the flowers are distorted.

Life Cycle: Cyclamen mites were first reported in the United States about 1900. It has since become famous as a harmful plant pest. Cyclamen mites seem to avoid the light; they occur in hidden areas on plants ( buds and between the calyx and corolla and the stamens and ovaries of flowers). This mite also prefers high humidity. The eggs have delicate shells that can often be found collapsed among masses of unhatched eggs and mites. Deposited in moist, dark places and in small groups, the eggs require about 11 days to hatch. The mites molt only once.

MANAGEMENT STRATEGIES Cultural control: Immersing infested plants (pot and all) into water heated to 43° C for 15 minutes kills cyclamen mites without harming most plants.

Pesticides: If chemical control is desired, spray or dip the plant thoroughly with a miticide. For specific chemical control recommendations, consult the Cooperative Extension Service.

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