Lords Environmental - Gladiolus Thrips


Taeniothrips simplex

The gladiolus thrips is one of the most serious pests attacking gladiolus.


Damage occurs both to the corms in storage and to the growing plant. Infested corms are sticky, corky and russeted by the feeding of the thrips, and sometimes small rootlets are injured. Such damage usually results in a retardation of growth, poorer flowers, and smaller corms. Some corms may fail to germinate.

The growing plants show whitened or silvered streaks on the leaves and flowers due to the thrips feeding. Buds may be injured so severely that they new open normally, they turn brown and the bud sheaths dry out and become straw-colored. Leaves also brown and die.

Adult female gladiolus thrips are about 1/16 of an inch long, shiny black with a conspicuous white band at the base of the front wings. Males are slightly smaller and the white band is not so conspicuous. The nymphs (immatures) are about 1/50 of an inch long, and when full grown are a pale yellow color.

The gladiolus thrips overwinter on the corms. Under favorable conditions of humidity and temperature all stages may be present. Thrips may reproduce at temperatures of 60 degrees F or above.

In the spring thrips are carried into the field on the corms and start a new cycle of infestation. As new stems appear, the thrips crawl inside the leaf sheath which offers excellent protection for their development. When the flower spikes develop, the insects crawl into the bud sheath where it is practically impossible to reach them with sprays or dusts.

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Lymantria dispar

The gypsy moth is one of the most important forest pests in the Northeast. The caterpillar feeds on leaves of forest, shade, ornamental and fruit trees and shrubs. A single defoliation can kill some evergreens, but usually two or more defoliations are needed to kill hardwoods.

Besides causing destruction or decline of the trees, loss of aesthetic, recreational and watershed values of ornamental trees, parks and forests occurs. Caterpillars cause a public nuisance.

The favored hosts include the white and red oak groups, willows, some poplars, speckled alder, basswood, fruit trees (especially apple) and gray and river birch. Small larvae chew pin holes in the leaves whereas larger larvae either partially or completely consume the leaf from the outer margin inward.

The 1 1/2 inch long by 3/4 inch wide (38 x 19mm) egg masses are covered with a dense mat of buff colored hairs. They are often found on trunks of trees or underside of larger branches. Current year egg masses have a good buff tan color and are hard and velvety to the touch; older ones are faded, and soft to the touch as the eggs have hatched.

Small larvae are dark brown to black and very hairy. As they reach maturity they become slate colored and have 2 rows of blue spots (5 pairs) followed by 6 pairs of red spots on the back. Fully grown larvae are 2 to 2 1/4 inches (50-56mm) in length.

Pupae are brown and teardrop shaped. A few threads of brown silk hold the pupae in place on the tree trunk.

Male moths are brownish with black markings and have a wingspan of 1-1/4 inches. Females have white wings with dark markings and a tan to buff colored body. Females are heavy bodied and do not fly.

There are four distinct stages to the development of the Gypsy moth - egg, larva, pupa and adult (moth). The eggs are round, black to brown in color, and deposited in masses of 100 to 600 eggs in July and August. The masses are covered with a dense mat of tan or buff colored hairs from the females body. The tiny caterpillar overwinters inside the egg shell, but does not hatch until the following April or May. When the eggs hatch, the 1/4 inch (6-8 mm) long caterpillars remain on the egg mass for a few days before climbing the tree to feed.

The young caterpillars also spin silken threads and hang down from the tree branches. Wind often breaks the threads and carries the caterpillars to nearby trees and shrubs. This is called "ballooning". Long range dispersal is aided by man - egg masses or pupae may be inadvertently carried on vehicles, outdoor furniture, plants and the like.

The female passes through 6 caterpillar growth stages; the male 5 stages. Each time the larva grows it sheds its skin and a new larger skin forms. The larval stage lasts for about 7 weeks.

In June and early July full-grown larvae may leave the host plant and seek out protected places to form the pupa or resting stage. At this time, the large caterpillars may be seen crawling across walkways or roads, or up the side of a house. The pupal stage lasts about two weeks. Moths emerge from the pupae - the males usually emerge first. Males are strong fliers and may be seen flying in a zigzag pattern during the daytime. The female does not fly, but remains near the pupation site and releases a sex attractant (pheromone) which attracts males. After mating she deposits her eggs in a single mass and then dies. There is one generation per year.
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