Aphids, whiteflies, and thrips, oh my!
The pests that trouble gardeners and commercial growers are numerous and varied. Outlined below, you will find photos of various pests and damage, along with physical descriptions that will help you identify most pests online. Identifying your unwelcome guests can be further simplified by hanging sticky traps (HORIVER) in the garden and greenhouse to collect samples. The HORIVER FIELD GUIDE can be very helpful in identifying these pests, both before and after they become stuck to the traps.
Aphis gossypii (Cotton/Melon Aphid), Macrosiphum euphorbiae (Potato Aphid), Aulacorthum solani (Glasshouse Potato/Fox Glove Aphid), Myzus persicae (Green Peach Aphid)
Aphids have always been a problem for the plant enthusiast and commercial grower. However, as time has passed, aphid infestations have become a more prominent problem, especially in the horticulture sector. As a result of their enormous reproductive capability, aphids can cause severe damage to a myriad of plants. In addition their ever-increasing resistance to pesticides greatly enhances their destructive capability. --BIOLOGY-- An aphid population consists of viviparous females. Young aphids are born and immediately start feeding on plant sap. They grow quickly and molt four times before they become adults. The resulting characteristic white skins left behind betray the presence of aphids. Winged adults develop at high densities, enabling rapid spreading to other plants from hot spot areas. --DAMAGE-- Direct feeding on plant sap, excretion of honeydew, and the injection of toxic substances cause crop damage. Plant growth is halted and leaves become curled. Honeydew dirties fruit and leaves, and is also a medium for the growth of fungus. Aphids can also transmit and spread viruses. --BIOLOGICAL SOLUTIONS-- Biological control of aphids is possible with the Koppert products listed below.
BLACK VINE WEEVIL
The black vine weevil is a pest that can cause enormous damage in many ornamental crops. The larvae of the beetle are not easily controlled chemically: not only because they are hidden in the soil, but also because of their acquired resistance to many pesticides. --BIOLOGY-- The black vine weevil goes through four stages of development: egg, larva, pupa, and adult. Adult black vine weevils are "walkers", i.e. they cannot fly. They are particularly active at night, and will go almost unnoticed during the daylight hours. The larvae live in the soil where pupation also takes place. --DAMAGE-- Both the adult weevil and the larvae damage plants. The adult weevil takes semi-circular bites from the edges of leaves, resulting in notching which decreases the ornamental value of the plant. The larvae, however, cause the most significant damage. Smaller larvae feed mainly on root hairs, while larger larvae feed on roots and the stem base. This greatly hinders growth, and eventually causes the plant to turn yellow and wither. One larva is enough to kill a plant if it girdles the base of the stem. --BIOLOGICAL SOLUTIONS Biological control of the vine weevil is possible with the Koppert product listed below.
Lacanobia oleracea, Chrysodeixis chalcites (Green Garden/ Tomato Looper), Spodoptera exigua (Beet Armyworm)
Caterpillars of several butterfly and moth species can cause extreme damage to a variety of plants, within a short period of time. --BIOLOGY-- The life cycle of butterflies and moths consists of four developmental stages: egg, caterpillar (larva), pupa, and adult. Eggs are often laid in groups on a leaf or on various greenhouse structures. The larvae or caterpillars have well-developed heads and strong jaws for chewing vegetation. --DAMAGE-- Caterpillars eat almost continuously, except when they are molting. Damage is caused by the gluttonous eating habits of the caterpillars when leaves, flowers, fruit, and growing points are consumed. --BIOLOGICAL SOLUTIONS- Adult butterflies and moths can be detected effectively with the help of pheromone traps. Biological control of caterpillars is possible with the Koppert products listed below.
Fungus gnats are a problematic pest, especially in young plants. They can cause damage to seedlings, rootstock, and cuttings of many plant species. They are most often found in moist organic environments. --BIOLOGY-- Fungus gnats go through seven developmental stages: egg, four larval stages, pupa, and adult. Adults are noticed when they appear in large numbers. Eggs are deposited in the soil, where all developmental stages take place. Larvae generally eat rotting plant material, algae, and fungi that are present in or on the soil. --DAMAGE-- Fungus gnats can cause both direct and indirect damage. Direct damage occurs when the larvae graze on the plant's roots. Indirect damage occurs when the adults spread diseases (fungal spores and plant viruses) or pests such as mites and harmful nematodes. --BIOLOGICAL SOLUTIONS-- Biological control of fungus gnat larvae is possible with the Koppert products listed below.
JAPANESE BEETLE GRUBS (LARVAE)
Popillia japonica (Japanese Beetle)
Japanese beetle grubs (larvae), along with other large white grubs are the cause of a great deal of damage to residential lawns and over 400 different species of broad-leaf plants. --BIOLOGY— Japanese beetle go through six developmental stages: egg, three larval stages, pupa, and adult. Adult beetles emerge from the soil from late June through July. From emergence through mid-August, the females go through multiple cycles where they feed, mate, and lay eggs, until they each lay a total of 40 to 60 eggs. Larvae will hatch within 8 to 30 days, depending on the soil temperature. By early fall, most of the larvae will have reached their third stage of development and are prepared to hibernate through the winter at soil depths of 4 to 8 inches. Around mid April, or when soil temperatures reach approximately 60 degrees F, the grubs move close to the surface to feed. --DAMAGE-- The adults eat the leaf tissue between the veins, leaving stripped leaves that die quickly. Adults also attack flower buds and fruit. In the soil, the grubs can kill young plants but most commonly affect lawns and turf via grazing on the roots. Damaged grass yellows, as if under water stress. This destruction generally occurs in the spring before the larvae pupate and in the fall after the new larvae hatch. Grass damaged by beetle larvae feels spongy and can be pealed up like a carpet, revealing the grubs. Heavy infestations will kill grass in large patches. --BIOLOGICAL SOLUTIONS— Biological control of Japanese beetle larvae and other white grubs is possible with the Koppert products listed below.
(Liriomyza trifolii (American serpentine leafminer), Liriomyza bryoniae (Tomato Leafminer), Liriomyza huidobrensis (Pea Leafminer), Liriomyza strigata
There are four leafminer species that have become common pests. Under normal conditions, several natural enemies effectively parasitize the larvae of these species. However, problems with leafminers have increased due to the widespread use of broad-spectrum pesticides. As with other pests, leafminers have developed a resistance to many of these chemicals. --BIOLOGY-- Both leafminer goes through six developmental stages: egg, three larval stages, pupa, and adult. The adult leafminers are small yellow and black flies. The larvae form mines in the leaves of plants, visible as a lacework of white lines. Pupation primarily takes place in the soil. --DAMAGE-- The larvae and female adults cause plant damage. The females make feeding marks in the leaves and lay eggs inside of them. As the larvae feed, they mine through the leaves reducing the amount of productive leaf surface area and eventually causing leaves to dry out completely. Indirect damage occurs when fungi or bacteria enter the feeding areas. --BIOLOGICAL SOLUTIONS-- Biological control of leafminers is possible the Koppert products listed below.
Mealybugs cause unsightly damage to many plants in the home, garden, and greenhouse. --BIOLOGY-- This pest has five developmental stages in its life cycle. The females go through the following stages: egg, three nymphal stages, and adult. The males go through the egg stage, two nymphal stages, the false pupa stage, and adult stage. Mealybugs derive their name from the third larval stage onwards, when the female's body is covered with a white wax-like substance in the form of powder, filaments, and projections or plates. --DAMAGE-- Nymphs and female adults cause plant damage. Adult male mealybugs do not feed. Most mealybug species feed on leaves, but some extract food from roots or form galls. Certain species may also transmit plant viruses. --BIOLOGICAL SOLUTIONS-- Biological control of mealybugs is possible with the Koppert products listed below.
Most mushrooms growers find mushroom flies to be a most challenging pest. --BIOLOGY-- Mushroom flies go through seven developmental stages: egg, four larval stages, pupa, and adult. At a temperature of 76 degrees F, development from egg to adult takes approximately 21 days; at 61 degrees this takes twice as long. Adults invade mushroom buildings containing freshly pasteurized compost. They are attracted by the smell of the compost and growing mushrooms. Each female can lay up to 170 eggs in the substrate. --DAMAGE-- Emerging larvae feed on compost, destroying structure and water retention capacity that inhibits growth and reduces yields. Larvae also feed on the developing mushrooms, making them unsaleable because of the damage that occurs. The adult flies are a constant nuisance to picking staff, and are known to be vectors of harmful funguses, bacteria, nematodes, and mites. --BIOLOGICAL SOLUTIONS-- Yellow sticky traps (HORIVER) are effective in detecting and monitoring adult flies. Effective control of mushroom flies is possible with the Koppert products listed below.
Tetranychus urticae (Two Spotted Spider Mite)
Spider mites are pests in many crops. Their immense reproductive capacity enables them to cause enormous damage in a short period of time. In many crops, the two-spotted spider mite is the most detrimental pest. Other spider mite species can cause damage as well. --BIOLOGY-- The spider mite goes through five stages of development: egg, larva, first nymphal stage (protonymph), second nymphal stage (deutonymph), and adult. All stages can be observed on the plant leaves. One of the characteristics of this pest is the fine webbing that is produced. --DAMAGE-- When large numbers of spider mites are present, plants may be completely covered with webbing. Larvae, nymphs, and adults cause plant damage. This pest feeds on the underside of the leaves, causing yellow spots to appear. Damage may quickly become serious, leading to decreases in both growth and production. Subsequently, plants may easily die from a heavy infestation. --BIOLOGICAL SOLUTIONS-- Biological control of spider mites is possible with the Koppert products listed below.
Frankliniella occidentalis (Western Flower Thrips), Thrips tabaci (Onion Thrips)
Both the western flower thrips and the onion thrips are major problems in many plants, especially ornamentals, sweet pepper, and cucumber. --BIOLOGY-- Thrips go through six stages of development: egg, two larval stages, pre-pupa, pupa, and adult. Mature thrips are found in flowers and on leaves, where they deposit their eggs. In sweet pepper, the egg laying sites are easily recognized as wart-like deformities on the leaves. The larvae feed on all above ground parts of the plant and are extremely mobile. Pupation takes place on the ground. --DAMAGE-- Thrips primarily cause damage to the plant by piercing and sucking dry leaf surface cells. As a result, photosynthesis is significantly reduced. At high pest densities, fruit damage can occur, e.g. in cucumber, damage to the young fruit causes distortions called "pig-tails". In ornamental plants, flowers and leaves may be scarred. Apart from this direct damage, thrips can also transmit plant viruses. --BIOLOGICAL SOLUTIONS-- Biological control of thrips is possible with the Koppert products listed below.
Tomato Pinworm Larvae damage tomatoes by feeding on leaves, stems, and fruit. Initial injury usually appears as a small leaf mine. Later injury includes leaf curling. Mature larvae can bore into the fruit, leaving a small pin-size hole. Plant tissues usually becomes infected and the fruit rots. Seedlings may be killed by the tomato pinworm. Tomato pinworm can be controlled by using the pheremone mating disruptor spirals, NO-MATE TPW.
Viruses can cause significant plant damage. This picture shows damage to tomato plants from Tomato Spotted Wilt Virus (TSWV). You can test plant suspect plant tissue with the Koppert Virus Test Kits listed below.
Bemisia tabaci (Sweet Potato Whitefly), Trialeurodes vaporariorum (Greenhouse Whitefly)
Both the greenhouse whitefly and the sweet potato whitefly are major pests of many vegetable and ornamental crops. Due to its resistance to many insecticides, the sweet potato whitefly poses a particular threat to many crops. --BIOLOGY-- The whitefly goes through six developmental stages: egg, first, second, third, and fourth larval stage (which develops into pupa) and adult. Adult whiteflies can usually be found in the top of the plant and on the undersides of young leaves, where they usually deposit their eggs. When shaking infested plants, adults will first fly, then return to the undersides of the leaves. Larvae are primarily found on the undersides of young leaves, though those of the sweet potato whitefly can occur on both young and old leaves. Pupae are typically found on the oldest leaves. --DAMAGE-- Both whitefly adults and larvae extract food from the plant. The larvae, in particular, secrete honeydew while feeding; giving the crop a “dirty” appearance and causing both stunted growth and sticky unsightly fruit. Plant viruses may also be transmitted. --BIOLOGICAL SOLUTIONS-- Biological control of whitefly is possible with the Koppert products listed below.
© Koppert Biological Systems, Inc. 2003