This article will help you identify, stop and control many common types of garden pests and diseases, including black spot on roses, cutworm, slugs and snails, verticillum wilt, aphids, root rot, anthrancnose, deer, grasshoppers and moles.
Blackspot on Roses: Black spot, a type of fungus, is one of the three major diseases that affect roses. It is very common and appears as black patches on leaves and stems, thriving in humid, rainy conditions. Put roses in a spot where there is good air circulation. This may help, but it's not a guarantee. As the fungus progresses, leaves turn yellow and fall off. Spores spread through air, water and dead leaves, and can survive the winter in the soil.
A good method to control the problem is to inspect the roses weekly, removing any leaves with black spots. Don't throw them on the ground; completely throw them away. Spray roses with a solution of one part lime to nine parts wettable sulfur in the winter. Remove infected leaves and throw them out. If a blackspot infection sets in, start regular applications of a fungicide. Benomyl and Daconil are two types that are most effective.
Cutworms: These are shiny, gray or brown caterpillars that eat plant stems at night. Some feed just below the surface, while others climb and feed on flower buds. Army cutworms move in groups, laying eggs on broad-leaved weeds or blades of grass. Signs of cutworms are severed stems, chewed leaves or holes in fruit. They do not come out during the day. To keep them away, sprinkle Diazinon on the soil around the plants.
Slugs and Snails: These pests thrive in dark corners of the garden, and like wet, shady areas. Irregularly shaped holes in your foliage are signs slugs and snails are probably at work. Rake away dead leaves, and empty pots or rocks. Make a barrier of eggshells, twigs or ashes around plants, as slugs and snails can't move around rough materials. Place half an orange upside down on the ground to attract them, and then throw it away. Sprinkle slug pellets or granules for effective chemical control, but be aware that slug pellets may harm birds, ground beetles and other creatures. Don't use these if you have young children playing in your yard.
Verticillium Wilt: This is caused by soil-dwelling fungi and attacks the roots. Leaves of infected plants turn yellow, wilt and die. Verticillium wilt infects about 300 kinds of plants, including tomatoes, roses, dahlias and strawberries. It's very common for tomatoes to get this disease, but the richer the soil the less it affects them. There is no cure for this disease. Fertilizer, rich soil and regular watering help plants resist infection. Look for varieties that are resistant.
Aphids: These are about the size of rice grains, and are black, red or light green. They suck the juice out of new plant growth. You can find them by turning over leaves. Wash aphids off with water, using insecticides available at most garden stores (always be sure to follow directions). Avoid using insecticides near harvest time for vegetables or fruit; instead insecticidal soap can be used safely up until the day of harvest.
Root Rot: This is a fungal disease living in the soil that eats away at roots. Foliage will look dull, begin to wilt, and turn yellow or brown. It will look like the plant isn't getting enough water, because the roots are destroyed or infected. Root rot occurs more in waterlogged areas or in soil with heavy clay. The best method is to improve drainage around plants. Use fungicides as a last resort.
Anthrancnose: This is a type of fungus that affects mainly sycamores, elms, ash trees, tomatoes, beans, privets, citrus, sweet peas and apples. Wet plants can spread spores. They cause yellow, brown or reddish spots on leaves. Seek resistant varieties of plants. Rake up fallen leaves, prune off infected twigs in fall and winter, and pull out any affected plants. Some types of this fungus can be controlled using fungicides. Read labels on any chemicals.
Grasshoppers: They feed on grasses and many garden plants. Usually they are only a minor garden pest, but sometimes the right environmental conditions allow huge populations to develop. Usually birds, bats, flies, beetles and rodents keep them under control. Turn over the soil in the fall to expose their eggs to predators. During serious outbreaks, protect plants with cheesecloth. Grasshoppers can be attracted with containers of poisoned baits containing carbaryl. Late in the summer, if there are still a large number of grasshoppers, dust affected plants with sabadilla. Wear a dust mask to reduce irritation to nose and mouth. Always read labels.
Deer: Gardens that are near wooded areas are at risk for deer entering and eating various plants. Deer are partial to certain kinds of flowers, as well as most vegetables, fruit, nuts, bark, and small twigs. They don't like bone meal or Diazinon (or any granule that keeps insects away). Sprinkle these around the plants at least once every three weeks. Some gardeners use fences, but deer can jump fences. Wire mesh or bird netting is also suggested. There are also repellents in the stores. Be sure to follow directions.
Moles: Moles are mainly a problem in grass, although they do occasionally tunnel through gardens. Traps that stick in the ground usually miss. The easiest way to get rid of them is chewing gum. Roll up a stick of it and put it in their hole. The moles can't digest the gum and will die.