Aphids, broad mites, greenhouse whiteflies, greenhouse whiteflies, two-spotted spider mites, and western flower thrips are common pests within greenhouse-where sweet bell pepper plants (Capsicum annum)are grown. Insect and mite pests cause direct damage by consuming flowers and leaves aboveground, causing indirect damage by propagating diseases (e.g. viruses). Both types of damage can restrict yields and reduce plant growth. Below you will find information about these pests and plant protection strategies that can be used to decrease problems with pests of greenhouse-grown peppers.
Greenhouse Pepper Aphids and Insect Pests
Aphids have soft bodies with tubes, which or tails, protruding from the end of the body. Aphids may have a range of colors from green, black, yellow, to pink. As the aphid is not able to lay eggs, a single female will give birth to approximately 100 nymphs, each of which can then give birth to their own offspring. Rapid reproduction can lead to extensive population outbreaks within a short period of time due to the rapid reproduction rate of aphids. Aphids can remain active throughout the year in greenhouses under continuous pepper production.
In greenhouse-grown peppers, aphid species such as the green peach aphid (Macrosiphum euphorbiae) and potato aphid (Myzus persicae) are present. Potato aphids are 1.7 to 3.6 mm long while green peach aphids are 1.2 to 2.5 mm in length. Aphids feed on new terminal growth and on the underside of leaves, causing direct and indirect damage to greenhouse-grown peppers. By removing plant fluids through their piercing-sucking mouthparts, aphids cause direct damage to plants; they may also cause blossom yellowing and stunting. Leaves damaged by aphids may appear distorted, curled upwards or downwards, or have a white cast or molting skins. The indirect damage caused by aphids is related to honeydew excreted during feeding. A sweet, sticky liquid, known as honeydew, is used as a growing medium by certain black sooty molds, which may hinder pepper plants’ biochemical capabilities to produce food. Aphids can also be vectors of viruses such as the Cucumber mosaic virus.
There are four stages of life for the broad mite (Polyphagotarsonemus latus): egg, larva, nymph, and adult. Female adults are approximately 0.2 mm in length and oval-shaped. The female can lay between 30 and 76 eggs either on the underside of the leaves or in small fruit depressions. Nymphs and adults primarily eat on the undersides of young leaves, flower buds, flowers, and fruit. Broad mites infect pepper plants through the use of a toxin that causes twisted, hardened, distorted, and/or stunted terminal growth. Leaves may turn purple in color and curl downwards. Under severe broad mite infestations, the fruit may be scarred and discolored, with premature fruit loss. In addition, damaged fruit may not be marketable.
A greenhouse whitefly’s lifecycle includes the egg, nymph, pupa, and adult. The adults are winged and 4.5 mm long and have tough, powdery skin. Greenhouse whitefly adults hold their wings flat and parallel to their bodies. Female greenhouse whiteflies may lay up to 300 eggs on the underside of leaves during their 30- to 45-day lifetime. A single egg is a spindle-shaped egg attached to a short stalk. The eggs eventually turn gray and hatch about four days later into nymphs that move short distances on plants, finding a suitable place to settle down and feed. During the pupa stage, the pupa does not feed. The pupae possess elongated waxy filaments that surround their bodies. They are elevated in profile with vertical sides. The development process, from egg to adult, usually takes 14 to 30 days; however, this time frame may be shorter when the air temperature is warmer.
Whitefly nymphs and adults have piercing-sucking mouthparts. They tend to cause greater damage to plants since they feed more frequently. Moreover, greenhouse whitefly can cause indirect damage by producing copious amounts of honeydew, which causes leaf curling, leaf yellowing, chlorotic mottling, stunting, and wilting.
Twospotted Spider Mite
Twospotted spider mite adults are oval-shaped, yellow-green to red-orange, and oval-shaped. They have black marks on both sides of their body. Female adults live about 30 days and lay about 100-200 small grains of eggs per two-week period. In the underside of the leaf, the eggs are deposited in the veins. The eggs hatch into yellow-green, six-legged larvae that then mature into eight-legged nymphs and then develop into adults. Development can be completed from egg to adult within one to three weeks. Development can, however, take as long as 14 days for 21oC (7oF) and 7 days for 29oC (84oF) air temperatures. Due to the fact that two-spotted spider mites are very sensitive to drying up when exposed to ultraviolet light (sunlight), all stages of their life are found on the underside of leaves.
The two-spotted spider mite has piercing-sucking mouthparts that are used to feed on individual plant cells. This results in a reduction of chlorophyll content in leaves, which decreases the ability of plants to manufacture food through photosynthesis. Bleached foliage may appear light yellow to silver in hue, and fine mottling may be visible on the upper leaf surface. Infested leaves may resemble bronze, turn brown, and fall off pepper plants. Moreover, webbing may appear on the leaf undersides.
Western Flower Thrips
This species is approximately 2mm long, has slender wings and two pairs of hairy antennas. Limids and larvae are brown to yellow in color. The life cycle consists of an egg, two larval stages, two pupal stages, and an adult. Regardless of ambient air temperature, the life cycle takes two to three weeks, with an optimum temperature range of between 26 and 29oC (79-84oF). At these temperatures, the life cycle can be completed in seven to thirteen days. Females live about 45 days and lay about 300 eggs during their lifetime. The eggs are inserted into plant leaves.
Western flower thrips cause direct damage if they feed on pepper leaves and flowers directly. Western flower thrips have piercing-sucking mouthparts that allow them to feed within plant leaves. After inserting their mouthparts, western flower thrips damage the cells’ cells and ingest fluids. Birds with this behavior create scarring, distorted growth, and sunken tissues on the underside of the leaves. Black fecal deposits may also be found on the underside of pepper leaves. Western flower thrips may cause indirect damage by spreading the tospovirus Tomato spotted wilt virus. We recommend that all plants infected with a virus be discarded immediately. The economic losses caused by Western Flower Thrips may result from direct and indirect damage.
European Corn Borer
Borer entrance holes in large pods allow water to enter, causing fruit decay. European corn borer can seriously damage peppers through damage to the fruit and premature collapse of small fruits. If rotting is detected, the larvae may leave to infest new fruit. At this point, one larva can cause damage to several pods. Additionally, plants can break because of tunneling by the borers in the stems.
The European corn borer moth often congregates in tall grassy areas near field margins, called action sites. Females fly into fields at night to lay eggs. Weather conditions during egg-laying can greatly affect the severity of corn borer problems. In the spring, when the weather is mild, the moths tend to lay more eggs, while on noisy, windy nights moths are less active.
Eggs of the European corn borer are laid in mounds of 15 to 30 eggs per mass. They are round and flattened, and they interlock, much like fish scales. Sometimes they are placed near the midrib of pepper leaves. The shade of the egg determines how old it is: freshly laid eggs are white, then cream. The larva’s head can be seen when a prominent black spot is visible on the egg mass, indicating that the egg will hatch in around 24 hours.
As soon as the larvae hatch, they are about 1/16 inch long and crawl toward the pepper pods. Young larvae are not fed on pepper leaves, but rather move toward the calyx of the pepper pod within two to 24 hours after hatching. They are protected from insects and natural enemies once under the calyx.
In essence, there are two to three generations of bugs. Their first appearance occurs from late May to early June and then their second appearance occurs from late July through August. Occasionally, a third-generation occurs in early September. Most commercial pepper producers are likely to suffer problems with the second, or midsummer, generation.