Fungus Gnats infest the growing medium and roots near the surface. They eat fine root hairs and scar larger roots, causing plants to lose vigor and cause foliage to display characteristics of nutrient deficiency and disease. Common foliage conditions include paling and necrotic spots along the leaf margins and across the leaf surface. Root wounds will invite fungi like Pythium and Fusarium especially if the growing medium is soggy from overwatering or if the plants are nutrient stressed.

Prevent and eliminate fungus gnats with the following:

• Use Gnatrol (BTi-Bacillus thuringiensis israelensis bacteria) to drench the growing medium. May require multiple applications. This should be done even if you don’t see them, by the time you do they have already caused damage.
• Avoid soggy growing mediums – let the top 2 inches of the growing medium dry between waterings.
• Use yellow sticky cards placed at the growing medium surface to catch any gnats that have hatched and escaped the growing medium.

Spider mites are the most common pest found on indoor plants and cause the most problems. They are usually found on the undersides of leaves where they attack and feed off of the plants fluids. This feeding causes stippling, small spots seen on the top side of the leaf surface. If left untreated, a spider mite infestation will progress relatively quickly.

There are a few different species of spider mite, but all do the same amount of damage. Thankfully, if you carefully inspect the garden on a regular basis, you can catch this pest and immediately spray down all plant surfaces with a neem spray. Neem works great at eliminating spider mites as well as some other pests and various fungi like powdery mildew.

Spider mites thrive in warm and dry environments. Reducing grow room temperatures to 60°-70° F (10°-21° C) will discourage reproduction.

Often, the mealy bug is introduced to the grow room by the gardener. Bringing store bought plants into the grow room, or visiting the grow room after a walk in the yard can transfer this pest. Thankfully, mealy bugs are easy to control and don’t present a large scale problem like spider mites. Physically removing small numbers with a small implement or a q tip dipped in rubbing alcohol is an effective treatment. Larger populations can also be easily eradicated with homemade insecticidal sprays, pyrethrum, and neem.

Aphids suck plant juices from the leaves, causing severely affected leaves to wilt and die. This pest is known for transferring bacteria, fungi, and viruses to infested plants. Manual removal by crushing small populations followed by insecticidal soap sprays will be very effective. Repeat insecticidal soap sprays every 7 days for 3 weeks when dealing with larger numbers to ensure their removal.

Thrips are one of the least common insects found in indoor grow rooms. Tissue on the leaf surface is scraped away and then the juices are sucked out. Thrips are fast moving insects and can be hard to see. Often, they leave a trail of black specks (feces) on the leaf surface along with the damaged leaf tissue. Pyrethrum and insecticidal soap sprays applied twice over a 10 day period may be all that is needed depending on how well established they have become.

The best way to check for whiteflies is to grab a branch and shake it. Whiteflies will fly from the undersides of the leaves if present. These pests look like very tiny moths due to their large wing structure. Whiteflies like spider mites, lay their eggs on the undersides of leaves and cause similar stippling damage that is visible on the top surface of infected foliage. Whiteflies can be easily controlled by removing damaged leaves and thoroughly spraying leaf surfaces (top and bottom) with an insecticidal soap spray at 5 to 10 day intervals. Yellow sticky cards, strategically placed in the grow room, will also help get rid of these pests.