Every gardener faces some problems with the garden at one time or another. Environmental problems, insects and diseases can create havoc among the plants and often leave the grower stumped.
The best way gardeners have prevented problems has been to carefully examine the garden at least once a week. First a gardener looks at the entire space. Do the plants look healthy and vigorous? Is their color normal and bright? Then the grower examines a few plants closeup. Do they look healthy? Have they grown since the last examination? Do the leaves or any other plant parts show signs of nutrient problems? Taking a photographer’s x 4 or x 8 loupe, available at camera stores, the cultivator looks at the leaves of several plants. He asks, "Are there any abnormalities? Any insects or eggs on the undersides?"
The most common problems with plants are not pests. They are over watering, under watering and over-fertilization.
When the medium is waterlogged the roots cannot obtain enough oxygen. At the same time, anaerobic bacteria, which are active in oxygen free environments, attack the roots and produce ammonia. Plant leaves may curl under from lack of oxygen. Waterlogged medium is not usually a problem for hydroponic gardeners but may occur in a some planting mixes. One solution is to water the plant less.
Roots have a harder time drawing water as the medium dries. During the light hours, the need for water is especially acute. If the roots have no moisture; first the bottom leaves and then the entire plant starts to wilt. Water must be added before the leaves die, which can be only a matter of hours. The old myth that water stressing the plant increases potency is not relevant to indoor cultivation.
Slight chronic over fertilizing can cause the leaves to curl either upward or underneath. Heavy over fertilizing can cause the plant to wilt in a matter of minutes. When the soil medium has a higher concentration of salts (nutrients) than the plant, it draws water from the plant. The only solution growers reported to this problem is to get rid of the excess nutrient by rinsing it out. Once the plant starts to wilt, a few minutes may mean life or death.
The best way to deal with pests is to prevent them from infecting the garden. A smart gardener never goes to the indoor garden after being in the yard or around outdoor plants. S/he may inadvertently carry in pests. While they are kept in check naturally outdoors, they have a field day indoors in a much less hostile environment. Healthy plants should be kept away from infected plants and should not be handled after handling infected ones. The pests most likely to infect an indoor garden are mites, white flies and aphids.
Mites are not insects but arachnids, related to spiders. They are very small and look like small brown, red or black dots on the undersides of leaves. A blemish can be seen on the top side of the leaf where they have been sucking. The infection may not be noticed until after there are 10-50 of these on a leaf. Using a magnifier they will be noticed walking around on their eight legs when they are not sucking the plant dry. Mites thrive in a dry environment. High humidity and low temperatures slow them down.
Aphids are oval looking insects about 1/16 of an inch long that come in a rainbow of colors including white, green, red brown and black. They are soft skinned and are often farmed by ants which squeeze them for their "honeydew" which is a sugar concentrate. Aphids suck on plants looking for protein. The excess sugars are exuded onto plants and these areas become hot spots for fungal and other infections. Aphids breed very quickly, and like warm, dry climates. They are very susceptible to pyrethrum and dry up from soap sprays. The home made spray a grower developed works wonders against them.
Whiteflies look just like a housefly except they are only about 1/5-1/10 the size and are all white. They fly around the plants when they are disturbed. Whiteflies are susceptible to pyrethrum, but the best control is with Trichogamma wasps, which get them under control in just a few weeks.
In the past few years there have been giant strides made in the development of safe pesticides for indoor use. A few companies produce safe insecticides in aerosol form which release a measured spray periodically. The aerosols use environmentally safe propellants.