Caterpillars are a very active pest from year to year. They have ferocious appetites and will eat most any plant they find. Their nests are unsightly, their eating will injure plants and they readily migrate into most any structure making a mess along the way. This article will detail all you need to know about caterpillars and then explain how and what to use for controlling local infestations and nests on your property.
Caterpillars are 2 to 2.5 inches long. They are generally dark – mostly black – with a long cream colored stripe that runs down their back. Blue dots are commonly prevalent, along with other colored lines on their body. These lines may be brown or yellow.
Caterpillars will hatch from eggs in early spring. Though barely noticeable during this young stage, they will become active as local plant life starts to grow its spring foliage. It is this foliage the caterpillar larva need. They will eat what they can find and if the host tree or shrub on which they originate does not provide adequate food, they will migrate to local plants. For the next two months, the larva will feed during the day growing bigger and bigger. At night they will return to their host tree and start to spin a constantly growing “tent” in order to accommodate their ever increasing size. This tent will become more and more apparent as spring turns to summer. Generally unsightly, they are white and silky looking usually appearing where limbs of the host tree grow in two separate directions. This forked location provides a good strong foundation on which their nest can support the ever increasing weight of the local colony. These colonies will start out with several hundred caterpillars and “tents” can be as small as a soccer ball or as large as a small car!
By the end of June or early July, feeding larva will have reached maturity and will instinctively want to leave their nests. Tents will be vacated and caterpillars will be seen migrating in all directions with no specific destination. They will be seeking a place to hide and pupate but they aren’t quite sure where this place will be. During the migration, they will commonly crawl on homes. They will be seen on the sides of homes and will eventually end up inside if proper treatments are not done to keep them out. Once a comfortable location is found where they feel safe and protected, they will spin their cocoon and undergo metamorphosis. In another 2-4 weeks they will emerge as adults, find a mate and reproduce. Females will find a suitable host plant on which to lay eggs and once found, will leave 200-300 eggs on a branch held together with a sticky substance which is part of the egg laying process. Adults will then die off in late summer and the eggs will rest till next spring when larva will hatch and start the cycle all over again.
Caterpillars can do a lot of damage when they feed. Though their feeding only defoliates host plants and rarely causes immediate problems, plants which loose a lot of leaves will suffer later in the growing season. Besides looking odd with no leaves, they won’t be able to perform normal photosynthesis, they will have to spend a lot of time and energy growing new leaves to replace those which were lost and because of this, will be a lot more vulnerable to other problems like disease and parasites. In general, its not good to let caterpillars have their way when they identify a plant on which to feed.
Furthermore, caterpillar droppings will be found underneath host plants and will make a mess on cars or furniture. They eat a lot and consequently, they defecate a lot. These droppings will be found under any host plant and can become quite an issue if a large local population is feeding. Rarely will the droppings cause damage but they can if left to rest on certain car finishes, furniture and other surfaces. Be sure to clean up the mess if you want to avoid any such staining or burning.
As each caterpillar grows in size, the colony will make their “tent” larger. Though caterpillars start each season small and barely noticeable, they will grow to be over 2 inches in length and the nest “tent” will have to made bigger to accommodate each individual’s larger size. Since several hundred caterpillars may commonly live in any one tent, these nests will become significant in size over the course of a summer. Don’t be surprised to find nests the size of a basketball or larger. In general, such additions should not be welcomed in any tree or bush and if left untreated, expect more to be around the following year. Trees in which nesting is successful will tend to attract more from year to year as previous generations will instinctively know a good host plant. By allowing any nest to reside undisturbed on your plants you are basically inviting more to come around year after year.
And if the damage, droppings, or unsightliness of their nests isn’t enough to make these insects a bona fide nuisance, their annual migration surely will. This migration will come during the end of their larval stage. Once larvae have had enough to eat, they will start to leave the main nest in search of a good location where they can undergo metamorphosis. This last stage is a kind of semi sleeping stage where they won’t be moving or feeding. They like to choose secure and discreet locations for this change and seem to like man made structures just as much as any tree. It is not uncommon for any one house to have hundreds of these pupating caterpillars if left untreated. The migrating larva will be out in great numbers traveling in all directions from the main nest and if they encounter a home or other structure, chances are they will try to make it their home for the next month. Since there are so many small cracks and crevices for them to enter a house, expect to find some inside living areas. Some homes will actually get invaded each year if they are located in the migration path of caterpillars. During this time their house can be covered with larva which are simply looking for a good place to complete their life’s cycle.
CATERPILLAR CONTROL TREATMENTS
Fortunately, there are some very effective treatment options for controlling caterpillars. The most basic spray is THURICIDE and is nothing more than a concentrated bacteria. Though harmless to man or other animals, caterpillars which eat plants that have been sprayed with Thuricide will die after a few days. Thuricide can be sprayed on any plant, vegetable or fruit without posing a hazard and is a good preventive material to use – especially if you are treating before they arrive. Another preventive material that will help is to apply a band of INSECT GLUE around the trunk of any targeted tree. This non-drying material is applied with a spatula, spoon or butter type knife around the tree forming a protective band over which caterpillars cannot travel. If they try to walk over it, they will get stuck. This is an excellent protective treatment that will stop all insects from accessing beneficial plants.
CATERPILLAR CONTROL SPRAYS
Anyone growing an organic garden might want something that’s labeled and certified for use on your organic fruit and vegetable crops. There are several effective products we carry that are all approved and certified including BT GARDEN DUST. This product works like the Thuricide and uses the same active; you just sprinkle it out onto the plant and foraging caterpillers will die after they ingest treated parts of the plant. If you prefer to spray, go with either the MULTI PURPOSE INSECT KILLER or the ORGANIC 3 IN 1 CONCENTRATE. The Multi Purpose is one of the strongest organic concentrates we offer and will work for most any insect. The 3 in 1 is a unique concentrate because it combines three type of actives that will handle insects, mites and fungus. It’s kind of a “all in one” spray and we do sell a lot of it since it does so much making organic gardening a lot easier.
If you already have caterpillars feeding, you may want something a little stronger. For fruits and vegetables, the strongest material you can use is VEGETABLES PLUS. It uses Permethrin as the active ingredient and is both quick acting and long lasting. Treatments will last 1-2 weeks and will quickly kill off any which are present. It also has a repellency feature which means it will tend to keep new ones away. It has no odor and can be used on any type of plant without presenting a hazard.
Lastly, the strongest spray available for killing off caterpillars immediately is BIFEN. This concentrate should not be used on food crops but its excellent for all other trees and shrubs. It’s low odor and will both kill quickly and last a long time. Bifen treatments will last up to a full month and will take care of just about any pest that may want to forage on your plant. It too will tend to repel nuisance or destructive insects.
Use any of the SPRAYERS we have listed as options for applying these liquids and if you are spraying either Vegetables Plus or Bifen, be sure to add some SPREADER STICKER to the tank mix. This additive will allow the concentrate to better coat the target plant. When spraying plants, its usually hard to get good coverage because leaves have undersides that will mostly avoid direct spray. Spreader Sticker will help get coverage in these areas by dispersing the spray once it lands on targeted treatment sites. It will greatly enhance any spray and should be used when treating plants.
CATERPILLAR CONTROL DUST
For some gardeners, a Dust formulation is the more preferred material to apply. For caterpillar control, there are two good dusts. For garden crops, use some PERMETHRIN DUST. It will work much better than Sevin Dust and will last longer too. If you want to dust non-food crop plants, use some DELTAMETHRIN DUST. It’s longer lasting and stronger overall. If kept dry, treatments will be active for a month or more. caterpillars on the plant during the application will quickly be killed and the dust has a nice repellent quality sure to keep new ones from coming around. Use a HAND DUSTER for small application needs; the DUSTIN MIZER is best suited for large gardens.
CATERPILLAR CONTROL AEROSOL
If you have a bunch of nests you want to treat directly, there are two options. The Vegetables Plus or Bifen will work well for a quick kill. To treat active tents, wait till evening. This will insure all caterpillars have returned inside. Next, prepare the spray and be sure the sprayer you have will reach high enough to soak the nest. Using a stick or pole, poke 3-4 holes into the tent. Holes should be large enough to allow for treatment to penetrate but not too large that all caterpillars fall out. Once access holes are made, spray the solution you have already prepared onto the nest for a quick kill. Soak it to the point of runoff thus insuring the ones present will be killed and that there will be a lasting residual to get any that may be away. Another product that can be used for this direct treatment is HORNET KILLER. This product is generally used for bees and wasps but this unique formulation has been found to work well on caterpillars and has them listed on the label. You still need to poke 3-4 holes per tent prior to spraying them but once access points are made, soak the nest down with the Hornet Killer for a quick end to any that are inside. You should be able to treat 1-3 average sized nests per can.
If your home is being penetrated by the migrating caterpillars, there are two products which will both keep them from entering and kill them if they try. First, spray the entire outside of the home with some DELTAMETHRIN. This odorless concentrate mixes with water and can be applied to the foundation and up the side of the home a few feet to provide a barrier over which caterpillars will not be able to crawl. If the house already has caterpillars up in the eaves and under soffits, spray these areas as well. The Deltamethrin will kill off those present and then leave a good residual to keep them away. Though Deltamethrin can be used in the home on baseboards to control the caterpillars in living areas, PT-CYKICK is better able to get into cracks and crevices since it comes with a handy tube injector. Use it along baseboards, around window frames and up high by crown molding. caterpillars will remain active for a few days inside once they enter so its important to get a good treatment down as soon as possible or even before their migration has started. If not done early enough, expect to see a lot of adults hatching out of pupa cocoons in another month or so as adults.
Caterpillars are mostly considered harmless pests. However, their chewing and eating can cause damage and stress to a lot of trees and plants once they start their spring feeding. Keep them under control with Vegetables Plus Permethrin or Bifen spray. Use some Hornet Killer for directly treating established tents and on the house, Deltamethrin and some PY-Cykick will help knock out any activity. Treat early in the season to keep caterpillar numbers in check; kill off as many as possible once the season is in full bloom otherwise you will have that many more next season.