Colonies can usually be found on the undersides of leaves as well as on soft new shoot tips or buds. Black bean aphids cluster together and are noticeable because of their dark colouring. As they feed, they secrete a sticky, honeydew substance which drips onto lower foliage and often becomes covered in a sticky black mould.
Cabbage white caterpillar
Large holes in the leaves of brassica crops and nasturtiums are usually the work of cabbage white caterpillars. Before an attack you may notice large numbers of white buttlerflies around your plants, as they lay eggs. These hatch into larvae which make small holes in the leaves as they start to feed on them, becoming much larger as the caterpillars start to feed more vigorously. Caterpillars also produce small brown or dark green granular deposits as they feed.
Carrot flies, also known as carrot root flies, infect their host plant’s roots causing widespread damage to crops. The damage is caused as the fly larvae feed. Signs to check for are leaf discolouration, and holes or tunnels in the carrot. The holes often turn a rusty colour due to a fungal disease called carrot or parsnip canker which commonly infects the damaged area.
The adults are very small to moderately sized. They are similar to other leaf beetles, but characteristically have the hindleg enlarged to allow for the springing action of these insects when disturbed. Flea beetles can also walk normally and fly. Many flea beetles are attractively coloured; dark, shiny and often metallic colors. Adult flea beetles feed externally on plants, eating the surface of the leaves, stems and petals. Under heavy feeding the small round holes caused by an individual flea beetle’s feeding may coalesce into larger areas of damage. Some flea beetle larvae are root feeders.
Frog hopper and cuckoospit
Adult froghoppers jump from plant to plant; some species can jump up to 70 cm vertically: a more impressive performance relative to body weight than fleas. The froth serves a number of purposes. It hides the nymph from the view of predators and parasites, it insulates against heat and cold, thus providing thermal control and also moisture control. Without the froth the bug would quickly dry up. The nymphs pierce plants and suck sap causing damage, and much of the excess filtered fluids go into the production of the froth, which has an acrid taste, deterring predators.
Slugs and snails feed at night and are easy to spot. They leave behind unmistakeable silvery slime trails and decimated young plants, leaves and flower buds. During the day they tend to gravitate to dark, moist areas of the garden and greenhouse, or hide on the undersides of large leaves and under pots.
Wilted, stunted and dehydrated plants which may also be losing leaves. Foliage becomes covered in a sticky honeydew residue which in turn can lead to the development of dark sooty mould. You may be able to spot colonies of mealybugs on the undersides of leaves and in the leaf joints of plants. They’re usually pinkish in colour and protect themselves with a layer of white waxy coating. Mealy bugs can also attack the roots of plants, but are much more difficult to identify.
One sees the striking caterpillar more often than the moth. Its brilliant colouring which is presumably designed to deter predators. Found on Budlea The pupa over-winters in the topsoil in a cocoon of silk interwoven with crumbs of soil – beginning to learn about camouflage. The moth, which flies early from April to mid June, is well camouflaged naturally, and at rest would be very difficult to detect.
Small piles of earth around holes in soil, lawns, paths, and at the base of exterior walls. Adults may be in the house around fresh and stored food, and on sap-sucking pest-infested plants. Large swarms of flying ants appear in mid -late summer when the conditons are warm and dry. A wet summer may disrupt this event causing staggered swarming.
Rosemary leaf beetle
If the shoots tips of rosemary and lavender are turning brown and dying back it could be the sign of an infestation of rosemary leaf beetle. These small beetles feed on the new shoot tips causing them to die back. They’re easy to spot because they have metallic green and purple stripes across their backs. Their larvae, which are slug-like and pale grey in colour with a dark stripe down the side, also cause damage by feeding on the shoots as they grow.
They generally live on the under sides of leaves of plants, where they may spin protective silk webs, and they can cause damage by puncturing the plant cells to feed. Spider mites are known to feed on several hundred species of plant. Spider mites are less than 1 mm in size and vary in color. They lay small, spherical, initially transparent eggs and many species spin silk webbing to help protect the colony from predators; they get the ‘spider’ part of their common name from this webbing. Hot, dry conditions are often associated with population build-up of spider mites.
Technically this is a pest to humans, however, very useful in the garden. Wasps feed on all sorts of grubs and predatory insects which they take backe to their nest. These beautifully intricate nests are created from chewed wood pulp to make the quite robust paper structure. Inside the nest is the queens chamber which is around the size of an apple. During the winter months, the queen goes into hibernation while the rest of the nest dies off.
The whitefly is abundant and destructive. It damages plants by reducing vigour and causing them to wilt, turn yellow, and die.