Parsnip

A fly whose larvae tunnel through the roots of carrots (as well as parsley, celery and parsnip). Symptoms: rusty tunnels and galleries in the root, brownish-red discolouration of the foliage, a bitter taste and rotting of the roots in storage. Adults are attracted by the scent of damaged leaves. The adult carrot fly is a small fly, about 4-5 mm long, with a slender, glossy black abdomen, a rusty-yellow head, yellow legs and transparent, faintly iridescent wings - hence its Polish name 'polysnica' (the shiny one). The insect flies low over the ground and weakly, readily hiding in the shade of plants. The larva is legless, creamy-yellow and glossy, growing to 8-10 mm; it is the larva that causes the damage, mining shallow, winding galleries just beneath the skin of the root, which rust over and crack in time. Two generations usually develop during the season (locally a third): the first flights fall at the turn of April and May, while the most damaging, more numerous second generation feeds from August to September, injuring the roots just before harvest. The pest overwinters as a larva in roots left in the soil or as a puparium in the ground. The first sign is often a brownish-red, somewhat wilted discolouration of the foliage; once the root is lifted, rusty furrows and tunnels filled with dark droppings become visible. Damaged roots turn bitter, rot readily in store and become a gateway for secondary fungal and bacterial infections.

Small (1–3 mm) soft-bodied insects, green, black or pink, feeding in clusters on young shoots and the underside of leaves. They excrete sticky honeydew. The diagnostic feature that distinguishes aphids from other small sucking insects is the pair of siphunculi (tubular projections) at the rear of the abdomen together with a tail-like cauda; a single colony usually holds wingless forms (parthenogenetic females) alongside winged migrants that fly onto new plants in summer. In summer aphids reproduce parthenogenetically and viviparously over many generations, so the population builds up explosively; in autumn many species produce a sexual generation that lays overwintering eggs on the host, and host-alternating species move between a winter host (often a tree or shrub) and a summer host (a herbaceous plant). Feeding symptoms include curling, crinkling and distortion of young leaves, stunted growth, yellowing, and the shedding of buds and fruitlets. Abundant honeydew coats the leaves, and the sooty mould fungus that develops on it forms a black film which limits photosynthesis; the honeydew is fed on by ants, which in return defend the colony against predators. Aphids are also important vectors of plant viruses (mosaics among them), transmitting them from plant to plant even during a brief probing puncture.