Have you ever had a tree that was beautiful and full of green leaves one day, and then seemed to suddenly be bare? That tree may be the victim of an insect infestation. Insects can wreak havoc on your plant life and systematically destroy healthy trees. Watch out for these common pests to keep your garden and landscaping healthy:
These small, soft-bodied insects suck sap from the leaves and stem and can infest almost any plant or tree. They secrete a sticky substance called honeydew, which is a host for a fungus that causes sooty mold on leaves, branches, and trunks. They can also cause deformed or twisted leaves and stems, stunted growth, and yellowing leaves and stems.
Encourage natural aphid predators in your garden like ladybugs and lacewings by avoiding pesticides in the garden. For small or delicate plants, you can remove aphids by hand, or, for sturdier plants, use your garden hose to wash aphids off new growth. Water also removes honeydew and prevents sooty mold. You can also use non-toxic soap sprays to control heavy infestations.
Ambrosia beetles bore into wood to lay their then eggs and add fungi that are fatal to trees to the tunnels for larvae to eat. Infestation can be identified by the “frass” that the beetles push out of the tree, which can look like toothpicks or piles of sawdust. Damage includes rapid wilting of the crown and die-back of twigs and branches. An infested tree can die quickly in hot weather when water can’t reach the crown.
Ambrosia beetles will attack almost any tree species. In Virginia, ambrosia beetles have also been found on grapevines. Ambrosia beetles tend to attack stressed trees, but will also attack healthy trees. There are no systemic pesticide treatments for them. The best way to prevent infestation is to monitor your trees and provide plenty of water, sufficient nutrients, and mulch trees properly. Once a tree has been infested with ambrosia beetles, it should be removed to prevent spread.
There are three common types of caterpillar that can defoliate trees:
• Fall webworms create web “tents” at the ends of branches
• Eastern tent caterpillars build tents in the forks of tree branches
• Gypsy moth caterpillars don’t spin webs or tents
Fall webworms do most of their damage in fall; Eastern tent caterpillars and gypsy moths defoliate trees in spring. The tents created by fall webworms and Eastern tent caterpillars are obvious signs of damage, usually accompanied by defoliation as the caterpillars eat the leaves.
Use an insecticidal spray applied to the leaves to control fall webworms and Eastern tent caterpillars when the caterpillars are actively feeding (fall or spring). Avoid spraying the webbed tents – the spray won’t penetrate them. Gypsy moths are more difficult to control because they are spread by moving items that carry egg masses (such as firewood). Check surfaces for egg masses and remove any you find.
Scale insects feed on plant sap and cause dieback and even plant death. They look like overlapping fish scales and are found on twigs and branches. Adults do not move, protected beneath their domed covering where they lay and hatch their eggs. Immature scale insects have legs when they hatch in the spring which they use to find a spot to mature into their immobile adult form. For some plants, scale insect infestations can be fatal.
The best way to prevent infestation is to use an insecticidal spray while they are in their mobile, immature state before the protective adult covering forms. It can be difficult to determine the best time to spray effectively. Tree care professionals are trained to identify pest species and are your best bet for scheduling effective spraying.
Sap-sucking spider mites are tiny and almost impossible to see. They scrape the surface of leaves and create stippled, scarred leaf surfaces. Damaged leaves may also look yellowed or bleached, and if an infestation is left untreated, plants may die. Spider mite populations increase during hot, dry weather and are commonly mistaken for drought stress. If you’re not sure that damage is caused by heat/drought or spider mites, call your arborist for a professional inspection.
Conventional insecticides don’t work on spider mites, although dormant oil sprays and soap sprays can help to control mite and egg populations in winter and early spring before growth begins. For sturdier plants, you can wash off eggs and larvae by spraying a strong stream of water on leaves to wash off eggs and larvae and reduce immediate populations.
If you are concerned about insect infestation and don’t know what to do about it, give us a call! Our experienced, trained arborist will identify the source of damage and help you create a plan to save your trees.