Summer is in full swing with hot and humid weather. Gardeners are tasked with watering to keep plants thriving, and to add insult to injury, pests are on the rise.
Gardeners should survey frequently, looking for signs of problems. Finding an issue, identifying a cause and researching a solution can prevent a major disaster. There are insects and diseases that present similar symptoms.
There are over 1 million described species of insects, and while some can do major damage to a garden, not all insects are bad. Where would we be without pollinators? Ladybugs in both their adult and larval stages eat aphids. Knowing which insects are good, which are harmful and how to control the problem ones is important to a healthy garden.
Insects can multiply rapidly in warm, humid weather. Some insects are worse than others in some years, and some insects we expect every year. Some insects feed on weakened or stressed plants, while others like tender, new growth more. If you see problems on your plants, begin to investigate the culprit, and take action.
Inspecting insect damage
Insects feed in various ways — chewing, sucking, rasping and boring — so, identification should start with the physical damage. Insects with chewing mouthparts, like caterpillars, grasshoppers and Japanese beetles, eat holes in leaves or large sections of foliage. Insects with sucking mouthparts, like aphids, lacebugs and scale insects, do just that — suck sap. Think of it as inserting a straw into the leaf and sucking out the plant juices. Instead of holes in leaves, the foliage is marred with little specks. When left unchecked, populations increase, and the damage does too; the entire leaf surface may be silvery or speckled where the chlorophyll has been extracted. Mites and thrips have rasping mouthparts; they scrape off the top surface of the leaf and suck out sap. As the culprits are small insects, there are no holes in the leaves, and the damage is silvery in appearance. Boring insects — those that can bore holes in trees or in the stems of your squash plants — can be difficult to control. Wood-boring insects usually go after weakened trees. Once inside, they are difficult to kill, as they construct tunnels inside. Squash-vine borers lay eggs near the base of the plant. When the larvae hatch, they bore into the stem and tunnel through, killing the plants quickly.
Sometimes you can easily spot the pests, and sometimes you must investigate. Many insects use camouflage to mask themselves and blend in.
There are some common insects that we see annually on certain plants. When growing hardy hibiscus, the mallow sawfly may turn the leaves into lace. Cabbage worms can do the same to members of the cabbage family, and the tomato hornworm can feed on a tomato plant and destroy it quickly. Corn left unprotected is usually attacked by the corn earworm. Flea beetles are common on eggplants, and slugs love hostas. So, start by looking for the most common complaint.
When grasshoppers hit, it seems like the plague of locusts, as they feed on many different plants. The Japanese beetle is the bane of many a gardener and has been migrating southward in our state. Bagworms attack junipers and cedars first and construct their protective sacks out of the plants they are feeding on. Know good caterpillars from bad; learn to recognize the larvae of the good and the bad bugs.
Aphids are the rabbits of the insect world. These small insects give birth to living young, and when conditions are right, they can multiply at lightning speed. They can be green, yellow or black and often congregate along the stems or tips of tender, new growth. They suck sap and give off a sticky substance called honeydew. Where honeydew lands, a sticky substance results on car windows, patio furniture or plants. When left long enough, a black, sooty mold can form. Aphids attack flowers, vegetables, shrubs and even trees.
Other sucking insects that give off honeydew include whiteflies and scale. Whiteflies commonly attack gardenias. They look like specks of white dandruff flying off the plant. Eventually, the foliage will be covered in black, sooty mold. Scale insects and mealy bugs are also common on a wide variety of plants. Camellias commonly get tea scale, and crape myrtles have been plagued with crape myrtle bark scale. Golden euonymus is frequently attacked by the euonymus scale. Scale insects won’t kill a plant overnight, but left unchecked, they will multiply and gradually weaken a plant. Scale insects come in all sizes and shapes, from tiny white and black tea and euonymus scale to the hard armored scales and the white oyster scales.
Monitor gardens regularly. Decide how much damage is acceptable. When those thresholds are met, act. Look at what is available to control pests — physical barriers, sprays of water, pruning out damaged plants or organic or nonorganic sprays. Spraying is usually the last resort. When spraying, make sure the product is labeled to control your pest, and apply it at the recommended rate. Water well before spraying, or you can burn the host plants when it is hot and dry outside.
Gardening can be challenging, but the end results outweigh the difficulties. If you have problems in your garden and you don’t know the cause, take a sample or good photos to your local county extension office. Once you can identify the problem, you are on the road to solving it.