The females of these peculiar insects don’t look insect-y at all! Females of many species are not mobile and look like a wingless, legless lump on your plant. They are generally round with no apparent body parts. The males, however, do have wings and somewhat resemble small flies… flies that can’t fly very well. These general characteristics describe many species, but not all. This is a very diverse family of insects so there is often exceptions in physical appearance. Though they may not look like insects, these Hemipterans are related to aphids, whiteflies, and mealybugs.
Though often immobile, these insects can cause quite a bit of damage to a plant. They imbibe fluid from plants causing the plant to weaken. This can be seen by yellowing or dead areas of the plant including stems and leaves. They also excrete a sticky substance known as honeydew. This can cause sticky leaves and sooty mold while attracting ants that may protect them against predators and parasitoids.
They are native worldwide (except Antarctica) but species are mostly concentrated in South America and Africa.
Like many pests, scale insects thrive in warm conditions that they seek out.
Scale insects are fairly easy to manage if infestations are caught early. Infected portions of plants should be removed. You can also pull any scale insects off the plant using tweezers or dab them with rubbing alcohol or neem-oil. Regularly spraying your plants will also knock off any unwanted buggers. There are also many commercially available biological controls such as parasitoids and predators to keep populations in control. Many scale species are resistant to pesticides but many people have seen positive results using horticultural oils. These oils basically suffocate the insect. As always, there are some effective pesticides currently on the market but should be used as a last resort. Try to start with natural pesticides derived from neem oil before moving onto more potent chemicals.
Because these insects are so bizarre in appearance, they are often misidentified by gardeners as a disease. Though they may look dormant, these insects are very much alive and are constantly feeding on your tomato plants!