Insect activity increases during periods of warm, wet weather
By Norman Bezona
University of Hawaii at Manoa Cooperative Extension Service
Insects flourish in warm and wet weather, so August and September are often the peak time for their abundance.
Many are beneficial, and some even endemic, and should be protected. That is, they evolved in Hawaii and may be found nowhere else.
Others are injurious not only to plants, but to animals, including man. These include the Argentine Fire Ant, African Bees and many others. Unfortunately, some mean guys have found their way here and, once here, it is hard-to-impossible to eradicate them.
An example is the Little or Lesser Fire Ant that is established in Puna and ultimately may find its way in suitable habitat all over the island. This one is spread most often in potted plants being moved from infected areas. If you are in doubt when you have a new plant for your garden, you may bait these almost invisible guys with peanut butter on a small stick. There are baits available at your local garden shop to use for control, but once they overtake your garden, you will get some nasty bites.
The best way to help avoid new pests, is to support our Department of Agriculture inspectors who are trying to stop new potentially harmful insect introductions. Don’t try to bring any new plants or seeds to the islands without proper inspection and permits. I just heard a rumor the other day that someone shipped into Hawaii, young palm plant in soil from Florida without permits or inspection. That could possibly bring lethal yellowing disease as well. This disease is common in Florida and has killed ten of thousands of palms there.
As the weather warms, insects in your garden are on the increase and with ravenous appetites. Some feed on plants and others feed on plant eaters. It is important to keep a close watch now, since some are sneaky rascals. The moment you turn your back, they’re apt to zip out from a nearby host plant and begin munching on the best plants in the garden. Not only do insects feed on your plants, but they devour a gardener’s pride and prestige. One way or the other, you’ve got to learn how to get ahead of these creatures with chewing, sucking, piercing, or rasping mouth parts.
Some of the worst foes of shrubs and trees are thrips, whitefly, mites, aphids and scales. Young thrips are yellowish, minute, slender creatures. Mature thrips are only about 1/40th of an inch long. The little pests feed by rasping the plant surface and sucking the sap as it oozes from the wound. Thrips often fly to roses, crotons, and other ornamentals in huge numbers from nearby plants. The common Malayan Banyan is often loaded with thrips. Some nurseries are now carrying a variety of this plant that is resistant to thrips.
Aphids are a menace to tender shoots and buds because of their rapid reproduction rate. Aphids feed by sucking the sap from the tender plants, causing them to become deformed. These are especially common on citrus.
Nature may take a hand in controlling aphids. If you look at an army of aphids, you may spot a friend, the syrphid-fly larva, deflating the juice from aphid larvae at the rate of one a minute. Another aphid enemy — the Braconis Wasp — can deal a death blow to hundreds of the tiny pests by laying its eggs within their bodies of the friendly Lady Beetle may be gobbling up her share.
Red spider mites are eight-legged crawlers no more than 1/50th of an inch long. They are not true insects. Often there is quite a build-up of damage-dealing spider mites before you notice that the leaves are taking on an off-yellow color. A hand lens is needed to discover mites. You’ll find some mites are whitish and virtually colorless. Others may be tan, reddish or purple. Many mites thrive when it’s dry and populations decline with wet weather, so regular showers with the garden hose will reduce populations.
There are more than 20 species of scale insects that commonly attack plants. Scale insects fasten themselves tightly to the leaves and stems of many different kinds of plants and suck juice from them, turning leaves yellow, stunting growth and killing branches and sometimes even whole plants.
Among all the kinds of scale insects of many different shapes, sizes and colors, there are two major groups: armored scales and unarmored scales. As a rule, unarmored scale insects have softer shells and are larger than the armored ones. Unarmored scales almost always produce a sticky honeydew, while armored scales usually don’t. Often, you can notice ants searching for honeydew before you see the unarmored scales themselves.
Most kinds of scales cover themselves with a waxy coating making it difficult for insecticides to get to them. They are at their most vulnerable stage when recently born “crawlers” emerge from beneath the protective covering of the parent scale and move about, some of them for the only time in their lives. The crawlers travel until they find a good place to eat, then become stationary, begin to grow, and produce their protective covering.
The crawlers are too small to be seen easily, but if you’ve noticed the parent scales, you can assume that crawlers will emerge when plants start vigorous growth. Many predators feed on scale, so biological controls work for us if we are patient.
If beneficial insects, lizards and birds are doing a fair job of control, then relax. Nature tends to balance. By the way, did you know that we have more than a dozen lizards including skinks, geckos, anoles and even the African Jackson’s Chameleons that help control insects. Of course we have some frogs and toads. None are native.
Another interesting fact is that we do have snakes. Most folks don’t realize that we do have two species of snakes found in Hawaii. The first is an early 20th century accidental introduction called the Island Blind Snake. This harmless eight-inch fellow might be mistaken for an earth worm as it moves through the soil eating insects. The other is a native or indigenous species that is actually quite poisonous. Don’t worry though. It is only found occasionally in waters around Hawaii and is not aggressive. It is usually spotted in “El Nino” weather years. If you want to learn more, read “Reptiles and Amphibians in the Hawaiian Islands” written by Sean McKeown.
In the event that the unwanted insects are getting out of hand, your local farm and garden shop has a number of safe and effective pesticides available. Before using these products, read and follow label directions.
Individuals with home garden questions may call the Master Gardener Helpline in Kona at 322-4892 for answers. Call on Thursdays between 9 a.m. and noon Master Gardeners are also available during that time at the Kona Extension office in Kainaliu mauka of Aloha Theater. In Hilo, master gardeners are available to help on Monday, Tuesday and Friday from 9 a.m. to noon. The number is 981-5199.
They will also help by supplying information sheets and booklets on agricultural subjects.
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