Info about Insects (whitefly, thrips)

Whitefly (bemisia tabaci)

The Tobacco Whitefly (Bemisia tabaci) is perhaps the world's number one insect pest today, threatening agriculture worldwide. The damage caused by this tiny pest is twofold - not only can their infestation destroy individual plants by sucking out sap, but plant viruses that they can transmit can infect and destroy many different species of crops.

A suitable field crop can host billions of whitefly, with every female having the potential to lay up to 250 eggs. Of these, it only takes one insect to acquire a plant virus that can then be passed to each new plant that the adult sucks sap from. Once present in the plant, every subsequent whitefly that feasts on sap from that plant may become a carrier, transmitting the virus throughout the crop or even on to other plant species.

Prior to the early 1990's, whitefly infestations were a problem but not serious in comparison to other pests. Then, something alarming happened to the American whitefly population - they developed resistance to the commonly used insecticides. The insect was commonly referred to as a 'superbug' that could feed and breed, immune to most attempts to control it. In one year alone, this insect species cost US agriculture $500,000,000 in damage. The battle was on, to find ways to control these pests. Efforts to control the spread of this superbug were hampered by the discovery that infested ornamental plants, such as poinsettia were being shipped worldwide, spreading the insect to every continent.

The centre of the battle against whitefly pests such as these, is focused through the many scientists that comprise the European Whitefly Studies Network. As in any battle, the tactics used by both sides change and adapt to situations. To study whiteflies, colonies are usually established from field infestations then maintained inside controlled-environment rooms within purpose built facilities. Specimens from all over the globe are often collected, allowing the researchers to keep up to date with the rapid evolution of the whitefly and plant viruses they can carry. These facilities, which often include high containment laboratories, enable researchers to study the development of the pests under tightly controlled situations, investigating the effects of new pesticides, natural enemies and physical barriers such as nettings.

Klayman Meteor has developed few solutions to fight the white fly AntiVirus net, BioNet and the lately developed SpiderNet

Thrips

General Description

Thrips are very small, elongate, cylindrical, gregarious insects ranging from 1/25 to 1/8 inch (1-3 mm.) in length and 0.2 mm wide (.008") . The nymph are frequently pale yellow and highly active. The antennae and legs are relatively short. Adults are usually black or yellow-brown, but may have red, black or white markings and often jump when disturbed. They may have wings or may be wingless. If wings are present, they are long, narrow and fringed with hairs. For this reason, thrips are commonly referred to as fringed-winged insects.

Important Species

There are 264 species of thrips in the U.S. and Canada that feed on plants. Many other species are predaceous. The most common plant-feeding thrips on woody plants in Florida are:

banded greenhouse thrips	Hercinothrips femoralis
Cuban laurel thrips	Gynaikothrips ficorum
flower thrips	Frankliniella tritici
greenhouse thrips	Heliothrips haemorrhoidalis
redbanded thrips	Selenothrips rubrocinctus

Biology

Thrips undergo gradual metamorphosis. A general thrips life cycle is as follows. Female thrips deposit eggs in slits made in the leaf tissue by their sharp ovipositors. Each female lays 25 to 50 eggs which hatch (in two to seven days) into active nymphs. Immature thrips resemble adults, but the immatures lack wings and are lightly colored. These two nymphal stages are followed by two resting stages: the prepupa and pupa. The resting stages can be found either on the host or in the soil below the host. Under favorable conditions, the developmental period from egg to adult ranges from 11 days to three weeks depending on the species, hence, a population may increase quite rapidly. Parthenogenesis occurs in many species. When male thrips are present, they are usually smaller than the females.

Host Plants

Thrips attack an extremely wide variety of woody plants including azalea, ardisia, dogwood, gardenia, hibiscus, magnolia, maple, palm and viburnum.

Seasonal Abundance

Thrips occur throughout the growing season.

Damage

Thrips feed on the foliage and flowers, as well as young tissues in shoot apexes where the leaves are expanding. They puncture the plant cells with their rasping-sucking mouthparts and withdraw cell sap. Feeding activities produce bleached, silvered or deformed leaves and necrotic spots or blotches on flower petals. Eventually the damaged foliage becomes papery, wilts and drops prematurely. Thrips produce large quantities of a varnish-like excrement which collects on leaves, creating an unsightly appearance.

Sampling

To aid in detecting thrips, place a sheet of white typing paper beneath the leaves or flowers and shake the plant. The thrips will fall onto the paper and can be more easily observed and identified than when on the plant. Also look for the small spots of varnish-like excrement on the leaves. If plants are flowering, be sure to inspect the flower parts for thrips presence.

Since thrips are so small, use a 10 to 15-power magnifying glass. Blue-colored sticky traps have been developed for monitoring thrips and are available commercially. They appear to be somewhat more effective than yellow traps.