COMMON PLANT DISEASES
Canker – Canker develops where there has been damage to the bark of a tree or shrub. This could be from insects, sunscald, pruning, cold injury or mechanical injury. Infection spreads and can girdle a branch, causing the branch to fall off, or it can girdle a trunk and cause death. Many times the infection is isolated by a corky bark growth from the plant and the plant survives. Damaged areas are best removed as this part of the plant is weakened and could lead to more damage in the future.
Root Rot – Root Rot is a soil-born disease that can stay in the soil in decaying organic matter. It can be carried by wind or water and infect any host that has been stressed from any number of environmental causes or mechanical injury. The best defense against these diseases is planting species that are not susceptible or minimizing any unneeded or avoidable stress during the life of the plant.
Leaf Gall – Galls can be simple or complex growths on leaves or stems. Some are brightly colored. In most cases, they are unsightly but harmless to the plants. Some galls form when insects (certain wasps, midges and aphids) or mites feed on or lay eggs in leaves, twigs and stems. When feeding or laying eggs, insects can inject a toxin that stimulates rapid and abnormal growth.
Shothole – Shothole is a bacterial infection that is not usually serious. If it becomes a problem, however, the severity can be reduced by limiting overhead irrigation. It can also be treated with a bacterial spray.
Leaf Spot – There are thousands of leaf-spotting fungi and bacteria, most of which cause only cosmetic damage. Many of these organisms infect only one plant species. Fungal spores are spread by wind and water splashing the spores onto a leaf. Spots form wherever the fungus infects the leaf. This makes the spots very difficult to control completely, but the plants can be protected with a fungicide to keep the leaf spot from defoliating the plant.
Sooty Mold – Sooty molds grow from excretions (honeydew) that come from aphids, mealy bugs and soft scales as the feed on the plants. This is a sign that there are or were insects feeding on the plants, or on a plant above.
Powdery Mildew – Powdery Mildew is a parasitic fungus that penetrates only the epidermal cells of the host, producing an absorbing structure that diverts water and food to the fungus. This will eventually cause the infected areas to look distorted, dwarfed, chlorate, brown or have subnormal growth.
COMMON PLANT INSECTS
Aphids – Aphids can infest most garden plants. Some may spend their entire life on one plant, while others may move to less populated plants or to a better host plant. They are born from eggs and also live birth, and many generations can be produced throughout the year. Our systemic insecticide treatments are very effective on aphids, but there may need to be an additional application late in the year if the season is unusually wet.
Leaf Miner – Leaf miners are insect larvae that feed inside the leaf between the upper and lower surfaces. Adults lay their eggs inside or on the leaf and the larvae bore into the leaf and feed. Because they are inside, it is difficult to control them unless you use a systemic insecticide. Our early spring systemic insecticide treatment is very effective on these larvae. You may still see small tunnels, even on treated plants, where the larvae feed until it ingests enough of the insecticide.
Bagworms – Bagworms are the larvae of moths. These newly hatched caterpillars crawl around eating the foliage of a host plant. They build a bag with some of the foliage that they eventually attach to the plant and form a pupa. Several days later, an adult month emerges and lays its eggs inside the bag.
Mites – Mites are very small pests that infest many garden plants. There are many injurious species, including those commonly called spider mites. Mites are not insects; they belong to the animal class arachnida, along with spiders and ticks. Some mites may injure humans or animals; others are beneficial predators of plant pests. Control can be difficult because some mites complete their life cycle in 7-10 days and the egg stage is resistant to most chemicals. Scouting and proper timing of treatments are critical to good control. Repeat applications may be necessary.
Japanese Beetles – Japanese beetles are a non-native pest that was first seen in the early 1900’s. The adult beetles are active from June to October. The females lay their eggs in the soil and the grubs feed on roots in the fall until it gets cold. They move deep into the soil for the winter, and reemerge in the spring to feed on roots. They pupate and emerge as adults in May or June. Our early spring systemic insecticide protects plants from these beetles; however they must feed on a small amount of the plant to ingest the insecticide. If you see beetles feeding on treated plants, you should also see dead beetles around the base of the plants.
Scale – There are many different kinds of scale. Not all plants are hosts for scale, and some scale will only infest certain types of plants. They can be difficult to control because there is only a short period in their lifecycle in which insecticides are effective. If this narrow crawling stage is missed, the most effective control is to treat with a dormant oil that suffocates the scale.
Lacebugs – Lacebugs are very small, one-eighth-inch bugs that have delicate clear wings with many veins, giving them the appearance of lace. Capable of having several generations in one year, they damage plants by sucking the sap and cell contents from the underside of the leaves. Azaleas are a favorite host of these insects. Fortunately, our early spring systemic insecticide is very effective on these insects.