The tobacco moth scale insect is a pest that is widespread throughout Europe and has a host plant range of over 900 plants. Damage is caused by the transmission of plant viruses in addition to the sucking activity. Due to this transmission risk, non-European populations of the tobacco moth scale insect are listed as Union Quarantine Pests (UQS).
The tobacco moth scale insect is very similar in appearance and biology to the closely related greenhouse moth scale insect(Trialeurodes vaporariorum). Specialists can distinguish adults by the bristling of their hind legs, but their pseudopuparia can be recognized with some certainty even by laypersons because, unlike those of the greenhouse moth scale insect, they are shaped like shields.
Characteristic of the tobacco moth scale insects, which are about 1 mm in size, are the relatively large white wings. The eggs are yellow-green in color and stalked.
Adult females can lay up to 300 eggs. The eggs are laid preferentially on the underside of the leaves, where the larvae are also found. Initially the larvae are mobile, but from the second stage they are sessile. After passing through four larval stages, they pupate on the plant. At a temperature of 28 °C, the development period from egg to adult is about three weeks.
Heavily infested plants show yellowing on the leaves and are damaged by the sugary excretions (honeydew). The honeydew drips onto underlying leaves and fruits. Blackening fungi can settle on this shiny coating, resulting in so-called "sooty mold". On the one hand, this soils shoots and fruits, and on the other hand, affected leaves lose assimilation surface. This weakens the plants.
In addition to its sucking activity, the tobacco moth scale also causes damage by transmitting more than 100 plant viruses of the genera Begomovirus, Crinivirus, Carlavirus or Ipomovirus.
Until recently, the tobacco moth scale insect was mainly known as a pest of field crops of tropical and subtropical countries, such as cassava, cotton, sweet potato, tobacco, and tomato. However, the host plant range includes over 900 host plants from over 60 families, including composite (Asteraceae), cruciferous (Brassicaceae), cucurbitaceous (Cucurbitaceae), bindweed (Convolvulaceae), spurge (Euphorbiaceae), butterfly (Fabaceae), mallow (Malvaceae), and solanaceous (Solanaceae).
Due to the development of the highly polyphagous (uses many different plant species for food) subtype B, the tobacco moth scale insect has also become a major pest in the glasshouse in many parts of the world, attacking peppers, zucchini, cucumber, lettuce, and tomatoes, among others, or hibiscus, gerbera, gloxinia, and poinsettia ( Euphorbia pulcherrima).
Propagation and transmission
Tobacco moth scale can be transmitted in all stages of development with numerous plant species. Very often, however, their eggs, larvae and puparia are moved with young plants. Probably, the international trade in poinsettia (poinsettia) contributes particularly strongly to the spread of the pest.
Since the tobacco moth scale not only causes direct damage to plants through its sucking activity, but is also a vector of various pathogenic plant viruses, it is one of the most significant agricultural pests worldwide.
For some years now, enzymatic detection methods have also made it possible to distinguish between several subtypes of tobacco moth scale insect. The best known of these, subtype B, also known as the "silverleaf whitefly"(Bemisia argentifolii), has caused devastating damage to vegetable crops in California, is particularly prolific and highly resistant to insecticidal agents.
Prevention and control
- When buying in, an immediate check should be made for the presence of whitefly or for suspicious symptoms of damage (e.g. yellowish, chlorotic spots, honeydew, sooty mold).
- Monitoring using yellow traps is recommended before and during cultivation, especially for poinsettias and tomatoes.
- In general, regular infestation checks (especially for pseudopuparia in older leaves) should be carried out, and hygiene measures should be followed, especially after the end of a crop.
- Chemical treatment can be carried out with plant protection products (see list of plant protection products approved in Austria).
- In organic cultivation, the use of natural counterparts such as the ichneumon wasps Encarsia formosa and Eretmocerus eremicus or the predatory bug Macrolophus caliginosus is recommended.
Because of the risk of transmission, non-European populations of the tobacco moth scale insect are listed as Union Quarantine Pests (UQS) and are thus subject to legal regulations to prevent introduction and spread into or within member states of the EU.
Last updated: 25.05.2023