These small, soft-bodied insects are pear-shaped, measuring 1/16” to 1/4” long. There are approximately 4,000 aphid species worldwide, ranging in colors from green, yellow, brown, red or black. Adult aphids are typically wingless, but some can grow wings. On the tip of the head, there are two whip-like antennae, and on the back end, a pair of tube-like structures called cornicles.
Aphids are common on indoor and outdoor plants, including most edibles and ornamentals. They cluster densely on vulnerable new plant growth and suck plant juices from the undersides of the leaves. Plants can usually tolerate some aphid feeding without issue, but an infestation can result in stunted growth, leaf wilt, curling, yellowing and loss.
As the aphid feeds, it secretes a sticky brown fluid called honeydew. The gooey substance drips on to plant leaves, attracting ants and stimulating growth of black sooty mold.
Regular inspection of plants is necessary to prevent infestation. Aphids blend in well with leaves, so they may not be easy to spot at first. During certain times of the year, female aphids give birth to live young, which reach maturity and give birth to their own offspring within a matter of weeks. This exponential population explosion can result in a rapid infestation if left unattended.
Aphids can be eliminated using organic control techniques. To prevent an aphid infestation in your garden:
Thrips are very small (1/25”) straw-colored or black, slender insects that are difficult to see without a magnifying glass. These fast-moving insects have two pairs of feathery wings and are commonly found in greenhouses and outdoor gardens. There are over 6,000 species of thrips worldwide. Thrips reproduce rapidly, resulting in 15-20 generations each growing season.
Thrips damage plants feeding in large groups, sucking plant juices and scraping at fruits, flowers and leaves. They prefer new, rapidly growing plant tissues. Thrips can be found on fruit and vegetable crops, including asparagus, lettuce, cabbage, peas, carrots, beans and onions, along with many flowers, including roses. Adults and wingless larvae are attracted to white, yellow or light-colored blossoms.
Thrip infestation can be verified by observing their droppings, which look like black, shiny speckles, along with numerous silvery scars on plant parts, called stippling. Plant leaves may be pale or splotchy. Thrip feeding typically causes only moderate damage, but in severe cases, deformed growth may be observed. Thrip extraction of plant juices can sometimes prevent buds from opening. Some species of thrips can also spread tomato spotted wilt viruses.
You can control and prevent thrips by checking plants frequently and using these organic control techniques:
Whiteflies are soft-bodied, winged insects that are somewhat triangular in shape and as small as 1/12” long. They are closely related to aphids and mealybugs and have powdery white wings with short antennae.
These pests enjoy warmer weather and are often found in mid- to late-summer in most regions. Whiteflies inhabit outdoor gardens year-round in southern and coastal states, while northern regions tend to only see persistent infestations in greenhouse environments. They are active during the daytime, making them easier to spot.
Whiteflies damage plants by sucking plant juices and producing a sticky substance, called honeydew. This feeding causes the plant to weaken and leaves to wilt, turn pale or yellow. Plant growth may be stunted, and the honeydew left on leaves can attract ants and lead to formation of fungal diseases. Affected plants include indoor plants, ornamentals and vegetables such as tomatoes, eggplant, okra, peppers, citrus, sweet potatoes and cabbage.
Whitefly infestation can be confirmed by observation of swarms of winged adults flying around when affected plants are disturbed. About 200-400 eggs are deposited in circular clusters on the undersides of the plant’s upper leaves, hatching in just 5-10 days, creating the possibility of rapid infestation before the gardener realizes what’s happening.
Whiteflies can be controlled by checking your garden early in the morning for swarms and using these organic control techniques:
Mealybugs are pink, soft-bodied wingless insects that are covered in a white, waxy, cottony material. They appear on plant leaves and stems as white cottony masses. These bugs have long, sucking mouthparts that are called stylets, which are used to tap into plants and draw sap out of the tissue. Mealybugs range in size from 1/10” to 1/4” long.
Found in warmer growing climates, there are approximately 275 varieties of the mealybug across the United States. These plant suckers can cause problems in greenhouses, gardens and on indoor plants if higher numbers are present. Their feeding weakens plants and causes leaf yellowing and curling. Mealybugs also leave behind a sticky honeydew substance, which can lead to fungal diseases, if left unattended. Affected plants include ornamentals, houseplants, citrus fruits and avocadoes.
Visual inspection of plant leaves and stems is the best way to identify a mealybug infestation. Plants may look like they have cotton on them. On some plants, the pests may grow on the leaf tips, while other species of mealybug prefer to hide in the leaf whorls or stem crotches. There are also mealybugs that prefer to feed on roots, making them very difficult to identify without observing the root ball of the plant.
To control and eliminate mealybugs, be sure not to overwater or overfertilize, as these pests love new plant growth. Also, incorporate these organic control techniques:
Leaf rollers are small green or brown caterpillars that feast on leaves, buds and fruit. In the larval stage, these pests look like long, slender worms or caterpillars, just under 2/3” in length. They differ from other caterpillars because they have a tendency to roll leaves of plants together with a silken web, where they like to hide, live and feast.
There are a number of different varieties of leaf rollers, found commonly on fruit trees and ornamental trees. They are rarely found in vegetable gardens. When leaf roller larvae take up residence in unfolded leaves, the foliage will turn brown and die. Adults and larvae also feed within berries and fruit (think worm in the apple) and may not reveal themselves until consumption.
You should begin monitoring your trees early to identify the presence of leaf rollers, looking for folded or rolled leaves in the plants. Leaves may be discolored or show small holes in the leaves, which are signs of feeding.
To control and eliminate leaf rollers, be sure to begin organic treatment no later than petal fall to keep the larvae from injuring developing fruit. Organic treatment includes:
Scale insects are small, oval and flat. There are two types of scale insects: armored (hard) and soft. The armored type of scale insect is approximately 1/8” long and secretes a hard, protective coating over itself, which is tan to brown in color and not attached to the body. The soft scale insect is up to 1/2” long and secretes a waxy film that is part of the body. These oddly-shaped pests are mobile as nymphs (crawlers), but immobile as adults, resembling shell-like bumps instead of insects.
Over 1,000 species of scale insects exist in North America, inhabiting backyard trees, ornamental shrubs, greenhouse plants and houseplants. These are sap-sucking pests, attaching themselves to the undersides of leaves, branches and fruits of their hosts. The hard scale insects do not secrete honeydew, but soft scale insects produce excessive amounts of the sticky substance, which promotes growth of sooty mold, a black fungus that can interfere with photosynthesis in the plant. Scale insects thrive in warm, dry environments.
Scale insects can be found under leaves and at leaf joints. Plants affected by scale insects will look withered and sickly, with falling yellow leaves. The plants may also have a sticky sap or black fungus on leaves and stems and produce little new growth. Left unchecked, plant death is possible and scale insects will infest other plants.
To control and eliminate scale insects, observe the following organic gardening practices:
The spider mite is a tiny enemy of garden plants that is not really an insect, but a type of arachnid, related to spiders, scorpions and ticks. Adult spider mites are oval-shaped, reddish-brown or pale in color and only 1/50” long. Nymph spider mites look much the same, only smaller. Their size makes them very hard to detect in the garden.
Spider mites are very common throughout North America but tend to thrive in hot, dry conditions. They live in colonies, typically on the underside of leaves, feeding by piercing the leaf and sucking up plant fluids. They are very prolific pests, producing as many as 300 eggs over a few weeks, which can grow from egg to adult in as little as five days if weather conditions are right.
Greenhouses are especially susceptible to the destruction of the spider mite, but this pest attacks a variety of indoor and outdoor plants, including:
Identification of spider mites can be challenging, due to their size. Visible damage begins to occur when infestations are large. Leaves may show patterns of tiny spots, which are the pests’ feeding marks. As feeding continues, the plant’s leaves will turn yellow and may curl and fall off. Tight webs found under leaves and along stems are a visible indicator that spider mites are present. While the spider mite does not have wings, it uses its webbing to surf along the wind and affect surrounding plants. This is why it is important to contain and dispose of affected plants to avoid further infestation.
To control and eliminate spider mites, an organic treatment is best. Chemical pesticides actually encourage the spread of spider mites by killing beneficial insects that prey on them. Use this organic approach for best results: