Tomato Pests
Category: Insects
Aphids in Tomatoes
Symptoms
Small, soft-bodied insects found on the undersides of leaves and/or plant stems; usually green or yellow in color, but can be pink, brown, red, or black depending on the species and host plant; if aphid infestation is heavy, it can cause yellowing and/or distortion of leaves, necrotic spots on leaves and/or stunted shoots; aphids secrete a sticky, sugary substance called honeydew, which promotes the formation of sooty mold on plants.
Cause
Insect.
Disease Development Conditions
Distinctive features of aphids include the presence of cornicles (tubular structures) protruding backward from the insect's body; aphids usually do not move very quickly when disturbed; aphids can also transmit plant viruses to the plant when they feed.
Control Methods
If the aphid population is limited to only a few leaves or shoots, the infestation can be pruned to provide control; check transplants for aphids before planting; use tolerant varieties if available; reflective mulches such as silver-colored plastic can deter aphids from feeding on plants; a strong spray of water can be applied to strong plants to knock aphids off the leaves; insecticides are usually only necessary to treat aphids if the infestation is very high – plants usually tolerate low and moderate levels of infestation; insecticidal soaps or oils such as neem or canola oil are usually the best control method; always check product labels for specific usage guidelines before use.
Beet Armyworm
Symptoms
The beet armyworm is a common pest found in tomato fields every year. In some regions, the beet armyworm can be the most important caterpillar attacking tomatoes. Eggs are laid on leaves in clusters covered with hair-like scales left by the female moth; there can be more than 100 eggs per cluster, but usually fewer. Newly hatched larvae feed together on leaves near the egg cluster and gradually disperse as they grow. Older larvae feed on leaves and fruits. Larvae are usually dull green with many thin, wavy, light-colored stripes on the back and a wider stripe on each side; there is usually a dark spot on the side of the thorax above the second true leg. However, color varies and some part of some populations lacks the spot. Adult moth is mottled gray and brown and has a wingspan of about 1 inch. The life cycle takes about a month in warm weather and there are three to five generations per year. The beet armyworm attacks both leaves and fruits, creating single or closely grouped circular or irregular holes. In processing tomatoes, fruit feeding is usually shallow and superficial as most wounds eventually dry out. When the processing package is for paste or juice uses, little loss occurs from feeding damage. However, loss is more significant when rotting organisms enter directly into the wounds and rot the fruit or when feces or caterpillars remain in the fruit. In fresh market tomatoes, the presence of holes results in unmarketable fruit. Caterpillars sometimes develop inside the fruit, causing damage similar to that of the tomato fruitworm, and can cause buds to drop by feeding on flower buds.
Cause
Insect.
Disease Development Conditions
The insect can go through 3-5 generations per year.
Control Methods
Organic methods for controlling beet armyworm include biological control by natural enemies that parasitize larvae and Bacillus thuringiensis application; there are chemicals available for commercial control, but most of those available for the home garden do not provide adequate control of larvae.
Colorado Potato Beetle in Tomatoes
Symptoms
The adult beetle is a black and yellow striped insect; larvae are bright red with a black head when they first hatch and change color to pink; larvae have two rows of black spots.
Cause
Insect.
Disease Development Conditions
Adult beetles emerge in the spring; female beetles lay eggs in groups of up to two dozen; eggs are orange-yellow in color and are laid on the undersides of leaves; a female can lay 500 or more eggs over a period of four to five weeks.
Control Methods
Control of the Colorado potato beetle can be difficult as they develop high levels of insecticide resistance; adults and larvae should be hand-picked from plants and destroyed in soapy water; Bacillus thuringiensis applications can be effective in larval control but must be applied frequently; some insecticides, including spinosad, are still effective against adult beetles.
Worms
Symptoms
The larvae causing damage are usually active at night and hide in the soil at the base of the plant or in plant debris of the toppled plant during the day; larvae are 2.5–5.0 cm long; larvae can exhibit various patterns and colors, but usually curl from dirty gray or brown to black, with dark spots or stripes, and curl into a characteristic C-shape when disturbed.
Cause
Insect.
Disease Development Conditions
Worms have a wide range of hosts and attack vegetables including asparagus, beans, cabbage and other crucifers, carrots, celery, corn, lettuce, peas, peppers, potatoes, and tomatoes.
Control Methods
Remove all plant residues from the soil after harvest or at least two weeks before planting, this is especially important if the previous crop was another host such as alfalfa, beans, or a legume cover crop; plastic or foil rings fitted around plant stems to cover the bottom part 7.62 cm above the soil line and extending a few cm into the soil can prevent larvae from cutting plants; spread diatomaceous earth around the base of plants (this creates a sharp barrier that will cut insects crawling over it); if not growing organically, apply appropriate insecticides to infested garden or field areas.
Flea Beetle in Tomatoes
Symptoms
They create small holes or pits in leaves, giving the leaves a characteristic “shothole” appearance. Young plants and seedlings are particularly susceptible; plant growth may be reduced; if damage is severe, the plant may die; feeding damage can also occur on the fruit; the pest responsible for the damage is a small (1.5–3.0 mm) dark-colored insect that jumps when disturbed; the insects are usually shiny in appearance.
Cause
Insect.
Disease Development Conditions
Flea beetles can overwinter on nearby weed species, in plant debris, or in the soil; the insects can go through a second or third generation within a year.
Control Methods
In areas where flea beetles are a problem, it may be necessary to use floating row covers before the emergence of the insects to provide a physical barrier to protect young plants; plant crops early to allow for seed planting before the insects become a problem – mature plants are less susceptible to damage; trap crops can provide a control measure – cruciferous plants are best; applying a thick layer of mulch can help prevent insects from reaching the surface; application of diatomaceous earth or oils such as neem oil are effective control methods for organic growers; application of insecticides containing carbaryl, spinosad, bifentrin and permethrin can provide adequate control of insects for up to a week, but will need to be reapplied.
Hornworm in Tomatoes
Symptoms
Hornworms can ruin your tomato crop in record time. They hide very well among green leaves. This pest species can have a length of 12 cm. They do the most damage in the caterpillar or larva stage. They are pale green with white and black markings, and also have a horn-like protrusion from their rear. The caterpillar's green body also has eight V-shaped stripes. Tomato hornworms come from a mottled brown-gray moth. It causes large holes in the product and leaves with severe defoliation; if you see eaten flowers and/or scars on fruit surfaces, you may have tomato hornworm. The fruit may also suffer from sunscald due to reduced leaf cover.
Cause
Insect.
Disease Development Conditions
In late spring, large adult moths lay eggs on the undersides of leaves, which will hatch within a week. Adult moths are easily recognizable; they are often called sphinx or hummingbird moths. Caterpillar larvae will hatch in late spring and feed for 4-6 weeks before forming a cocoon and overwintering as pupae in the soil. If the weather is warm enough, larvae may burrow for as little as 2-3 weeks. Moths will emerge in the spring and then lay eggs again. In warmer climates, more than one generation per year may be possible.
Control Methods
Hornworms tend to start feeding from the top of the plant; look for chewed or missing leaves. Look closely at the tops of your tomato leaves to see if there are dark green or black droppings left by larvae feeding on the leaves. Then look at the underside of the leaves. If you have the time and patience or a small garden, hand-picking is an excellent tactic for control. Caterpillars are not dangerous and can neither sting nor bite. If you are hesitant to crush these large insects, drop them in soapy water (or give them to your chickens if you have any). If the hornworm population or the area of your garden is too large, insecticides can be effective, although they should be a last resort. You can use the organic pesticide Bt (Bacillus thuringiensis), a bacterium that acts as a stomach poison on some larval insects (but does not harm other plants and animals). For Bt to be effective, it must be ingested by the caterpillars and reapplied to plant leaves after rain. Please consult your local cooperative extension for a list of approved insecticides in your area. Insecticidal soaps also kill hornworms, but the pests must come into direct contact with the substance. Till the soil at the beginning and end of each gardening season to destroy overwintering larvae. Tilling has been shown to cause up to 90% mortality. Try planting dill or basil to keep hornworms away from tomato plants next year.
Tomato Fruitworm
Symptoms
Holes in tomato fruit, including entry holes near the stem end; feeding turns the inside of the tomato into a watery cavity filled with skins and rot (insect feces); damaged fruits ripen prematurely; young caterpillars are cream-white with a black head and black hairs; older larvae can be yellow-green to almost black with thin white stripes along their bodies and black spots at the base of the hairs; eggs are laid individually on both upper and lower leaf surfaces and are initially creamy white, but develop a brown-red ring after 24 hours and darken before hatching.
Cause
Insect.
Disease Development Conditions
The adult insect is a medium-sized moth, pale green to bronze; it can be one of the most damaging pests of tomato; insects overwinter as pupae in the soil; the insect is also a harmful pest of corn and is also called the corn earworm.
Control Methods
Early treatment of tomato fruitworms is necessary because they are protected from sprays once they enter the fruit; monitor plants for eggs and young larvae as well as natural enemies that can be harmed by chemicals; Bacillus thuringiensis or Entrust SC can be applied to control insects on organically grown plants; appropriate chemical treatment may be required for control in commercial plantations.
Tomato Moth Tuta Absoluta
Symptoms
It creates thin, white, winding paths in the leaves. It can cause white spots on the leaves and leaves falling prematurely from the plant; early infestation can cause a decrease in fruit yield; the adult leafminer is a small black and yellow moth that lays its eggs on the leaf; larvae hatch and feed on the leaf interiors.
Cause
Insect.
Disease Development Conditions
Origin and distribution of Tuta absoluta (leafminers): This species originates from South American countries. In later years, the insect spread to Spain (2006), France, Italy, Greece, Malta, Morocco, Algeria, Libya, and Turkey. Additionally, the insect has been detected in Syria, Lebanon, Jordan, Iraq, Iran, Saudi Arabia, Yemen, Oman, and other Gulf countries. In Africa, it is spreading to Egypt, Sudan, South Sudan, Ethiopia, Uganda, Kenya, and Tanzania (in the East) and to Senegal and Nigeria in the west. (It spreads through infected fruits and packaging materials). Life cycle: Mature larvae fall from the leaves to the soil to pupate; the entire life cycle can take as little as 2 weeks in warm weather; the insect can go through 7 to 12 generations per year. Yield loss: If not controlled, the insect causes 100% yield loss. The larva feeds on apical buds, tender new leaflets, flowers, and green fruit, which makes it a serious pest in tomatoes. Host Range: This insect also attacks other solanaceous plants such as potatoes, eggplants, pepino, and tobacco. It has also been reported on many solanaceous weeds.
Control Methods
Natural enemies of leafminers normally keep populations under control; check transplants for signs of leafminer damage before planting; if planting new ones in the same place or nearby, remove plants from the soil immediately after harvest; keep the field free of weeds, especially Solanum, Datura, Nicotiana; use pheromone traps and white sticky traps to monitor and control insects; use insecticides only when leafminer damage is detected as unnecessary spraying will also reduce populations of their natural enemies.
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