Pests and Diseases

The 5 Most Hated Indoor Garden Pests

David Kessler from Atlantis Hydroponics introduces the five indoor garden pests you really don't want to shake hands with!

All gardeners eventually face the problem of pests in their gardens. Whether you are a small home grower, or a large scale commercial farmer; bugs do not discriminate! In the state of Georgia alone agricultural production in 2004 amounted to $6,107,025,000.00, while the damage caused by insects totaled $176,638,487. Farmers spent an additional $677,589,590 trying to protect their crops. That’s over $854 million dollars combined; and you thought spider mites cost you a fortune! Indoor growers have an even more difficult situation when it comes to harmful garden insects; there is no rain to wash insects from our plants, there are no natural predators (unless we introduce them), our insecticide choices are limited because we grow in structures where people live, and to top it all off, the insects have become immune to many of our available pesticides. Damage to crops grown indoors are predominantly caused by 5 insects: spider mites, thrips, aphids, whiteflies, and fungus gnats .

Red and two-spotted spider miteSpider mites are probably the most common uninvited garden guest when growing inside. Often because of their small size (less than 1 mm), they may not be recognized until their population grows to the point of causing severe damage to your crop. However, there are a few telltale signs that you can look for that will make it easy to spot their presence in your garden. First, they produce a fine spider-like webbing, which if left unchecked will have your garden looking like it was decorated for Halloween. The second sign you have a problem is stippling (small specks or dots of yellow) on the leaves. This is caused by the mites piercing the leaf and sucking out the sap. One mite’s damage will likely go unnoticed, but a few hundred will make your leaves look like they were spray-painted yellow. If you think you have mites, take a white tissue and gently rub the underside of your leaves. If you see streaks of red (mite blood) then you probably have mites. A useful thing to keep in mind is that mites eat more when the humidity is low, so raising your humidity can slow them down, giving you more time to eradicate them. They also multiply faster in warmer temperatures, so try to keep your temperatures down if you have an infestation; it will make them more manageable as you attempt to get rid of them .

ThripsThrips are a very destructive pest. They are small (>1 mm), fast moving, and adults can often fly. Thrips come in an array of colors including green (the most common), brown, or tan. They often congregate near the veins of leaves. They can be hard to recognize except by the trained professional; however, the damage they inflict is unmistakable. The damage caused by thrips will look like small metallic black specks on the top of your leaves, often in areas of the leaf that have turned brown and dry from the sucking and rasping of the thrips. The black metallic speckling is their feces and can be easily noticed without any magnification. In warmer temperatures thrips reproduce and mature more quickly; making it advisable to keep your grow-rooms cooler when combating them .

AphidsAphids, although capable of causing large amounts of damage, are at least easy to see and identify because they are visible to the human eye. They can grow to be between 1 mm and 10 mm and can vary in color from colorless to green, black, brown, or pink. They tend to congregate at the top of the plant; as they have a preference for the newest, most tender growth. A less common but related pest is the root aphid, which attacks plant roots. As we do not have the opportunity to see our plant’s root system, root aphids are often not identified as quickly. The presence of ants in your garden should be a warning sign that you may have aphids. Ants are known to “farm” aphids; moving them around your garden from plant to plant. The ants drink the excrement of aphids which is a sugary substance known as honeydew. If the honeydew is not washed off of the plants, it acts as a perfect host for sooty mildew. Damage from aphids is often seen as contorted, yellowing or browning growth, dieback of growing tips, and a rapid decline in plant vigor .

White FliesWhiteflies derive their name from the white waxy covering on the adult’s wings and body. The adults are small and triangular in shape. They prefer to feed on the undersides of leaves. Although they are easy to spot, they can be hard to eradicate because when disturbed, they immediately abandon the plant and fly to a new host. Whiteflies suck the sap from plants, and a large population can cause leaves to turn yellow, appear dry or necrotic, and even fall off the plant. Whiteflies develop rapidly in warm weather and can quickly go from a small problem to a big one. Like aphids, whiteflies also secrete honeydew which can invite sooty mold(s) to grow on your plants .

Fungus GnatsFungus gnats are an almost guaranteed sight in all but the best maintained indoor gardens. The adult fungus gnats are tiny black or grey flying insects that look similar to fruit flies. They can often be seen flying about after watering your plants. They deposit their eggs in the top few inches of moist growing mediums, which then hatch into larvae that are tiny (3-4 mm) translucent/white worms with a black dot on their head. A female fungus gnat may lay up to 300 whitish eggs in clusters of 20 to 30 on the surface or in the crevices of potting media that is rich in organic matter. Although the adults are harmless, feeding mostly on algae and decomposing organic matter, the larval stage feeds on the tender root hairs and feeder roots, slowing plant growth and inviting bacterial infection .

All of the pests above are best controlled by prevention, early detection, and treatment, as well as sanitary growing practices. Using yellow sticky traps can be an excellent way to monitor pest populations and alert you to increases in pest pressure. This form of early detection can allow you to proactively treat your plants with an appropriate pesticide and closely monitor pest populations before they are capable of causing serious crop damage. Keeping your garden clean of debris and dying or dead organic matter such as leaves, and also keeping the floors free of dirt can reduce the likelihood of insect invaders. Lastly, be aware that all of the insects mentioned above either pierce, rasp, scrape, or suck on our plants; because they break the tissue of our plants, they are capable of transmitting viruses for which there is no cure other than to destroy the infected plant(s). So stay vigilant, keep your grow room clean, and take action early; and maybe you can have one of the few pest free indoor gardens.

Words: David Kessler, Atlantis Hydroponics.