Greenhouse whitefly (Trialeurodes vaporariorum Westwood) – a dangerous pest of vegetable crops in closed soil conditions

Abstract

The greenhouse whitefly (Latin Trialeurodes vaporariorum Westwood) is a broad-spectrum polyphagous insect that damages cucumbers, tomatoes, tobacco, and many other greenhouse and greenhouse plants. This species is observed on 27 plant species, and in general can damage more than 200 plant species from 82 botanical families. Adult insects and larvae are harmful, sucking the sap, causing yellowing of the leaf blade. With a significant population size and severe damage, plants are significantly behind in terms of flowering, fruit formation and ripening. Crop yields are significantly reduced. Sooty fungi (Cladosporium sp.) actively develop on honeydew secretions, which block the course of photosynthetic activity of plants. Stomata are partially, and sometimes even completely, closed by wax secretions. The development of larvae lasts 1–2 weeks, after which they stop feeding, the body thickens and turns into a nymph. The transformation of a nymph into an adult lasts 1.5–2 weeks. The development of preimaginal stages is highly dependent on temperature and at 12 °С is 60 days, at 17 °С – 43, at 22 °С – 30, and at 27 °С – 22 days. The lower temperature threshold for the development of eggs, larvae and nymphs is within 7.0–11.5 °С. The sum of effective temperatures for the development of 1 generation from egg to adult is about 400 °С. The influence of the type of food plant is less pronounced, although the difference in the duration of development is significant: on cucumber – 26 days, on tomato – 28 days, and on pepper – 30 days. The greenhouse whitefly is characterized by a focal distribution throughout the greenhouse. On one plant, adults, which feed on the upper leaves, and larvae and nymphs, which occur on the lower leaves, are usually found. The main part of the population (40–50 %) is represented by eggs, larvae make up 35–40 %, nymphs – 5–10 % and adults – 5–15 %. Chemical control is started immediately after the pest is detected in the cultivation facility. Delay in starting treatments leads to a rapid increase in the pest population due to the emergence of adults from pupae. Long-term use of insecticides belonging to the same group of compounds leads to the formation of resistant populations of the phytophagous plant. Given this, it is necessary to alternate treatments with preparations from different chemical groups. The biological method of con- trol consists in the use of the parasite Encarsia, predators (Macrolophus bug or Amblyseius mite) and biolog- ical preparations based on entomopathogenic fungi (Asherson, Boverin, Verticillin, etc.).