This thrips was described by Bouché in 1833 from specimens taken from a greenhouse in Europe as Thrips haemorrhoidalis. Packard described this species for the first time from this country in 1870 and called it the greenhouse thrips. This thrips appears in the Common Names of Insects approved by the Entomological Society of America as the greenhouse thrips, Heliothrips haemorrhoidalis (Bouché).
Distribution
This is a New World species although it was described originally from Europe. It was probably introduced into Europe on ornamental plants from tropical America. It is found on wild and cultivated plants in Brazil, the West Indies, and Central America. It occurs in the United States outdoors in central and southern Florida and southern California. It is found in greenhouses throughout the United States. Sometimes it escapes from greenhouses in warm months in states north of Florida. In Europe, it is found in Germany, England, France, Italy, Vienna, Finland, Palestine, and North Africa. This thrips can probably be found over much of the world due to its habits of living in greenhouses. It is a poor flier and remains in the shaded areas on the plant almost all the time.
Description
The eggs are white and banana-shaped and are inserted singly in plant tissue. The tip is usually visible with the aid of a hand lens. The early larval stage is whitish with red eyes. Larvae become yellowish after feeding. Mature larvae average about 1 mm in length. There are two larval instars and then it moults to the prepupal stage which is light yellow with red eyes and short wing pads. The pupal stage is slightly larger, with longer wing pads and larger eyes. It is yellowish and then darkens with age. The antennae are bent backward over the head in the pupal stage. The prepupal and pupal stages do not feed. The adult’s head and thorax darken to black while the abdomen changes from yellow, yellow-red, brown, and black. Cool temperatures retard the color changes. The legs remain a light yellow. The antenna has eight segments.
In Florida, this thrips is found especially on crotons, but has been taken from viburnum, dogwood, azalea, Vitis sp., palms, ardisia, orchids, avocado, philodendron, Crinum sp., Ficus nitida, natal plum, Coleus sp., maple, magnolia, mangoes, Aspidium sp., dahlias, ferns, guavas, hibiscus, phlox, pinks and many other ornamentals. In Palestine, it is reported on oranges and on Garcinia mangostana in Ceylon.
Economic Importance
This thrips feeds primarily on the foliage of ornamental plants. It attacks the lower surface first and, as feeding progresses and the population increases, the thrips move to the upper surface. The leaves become discolored and develop a distorted aspect between the lateral veins. In addition to the feeding damage, both surfaces are covered with small droplets of a reddish fluid, voided by the thrips, that gradually changes to black. Severely damaged leaves turn yellow and drop. In Palestine, the greenhouse thrips injures the leaves and fruit of citrus, but does not cause leaf drop. The damage of the fruit may be well defined depressed areas, often with irregular reticulation. This kind of damage occurs when fruit is immature. On mature fruit this damage is not well defined and merges into the healthy peel without a depression.
Management
Some of the early recommendations called for washing the leaves with a soapy water solution.