Getting Rid Of The Onion Hoverfly

2024 Author: Gavin MacAdam | [email protected]. Last modified: 2023-12-16 13:38

The onion hoverfly is found almost everywhere. Plants belonging to the lily and onion families suffer most from its attacks. However, the larvae of harmful flies can sometimes damage potatoes with tomatoes, as well as the testes of sugar beets and carrots. It is very important to notice the appearance of this pest on the site in time and start to fight it in a timely manner

Meet the pest

The chunky body of onion hoverflies is relatively small - from 5 to 10 mm, bronze-green in color, with a metallic sheen. The hind thighs of pests are slightly thickened, and on the top of their abdomens there are three pairs of whitish crescent spots.

The size of the oblong eggs of onion hoverflies ranges from 0.6 to 0.8 mm. All eggs are colored reddish-white and have a slightly pointed front end and a slightly rounded back end. The color of wrinkled larvae can be either pale yellow or grayish, and they reach 10-11 mm in length. The larvae themselves are endowed with a flat tummy and a rather convex back, and at the posterior end of their little bodies one can see reddish or brownish chitinized processes with a pair of spiracles. On the side of these processes, there are two triangular fleshy tubercles. The larval stage is characterized by three instars. The length of blackish-brown pseudococoons is up to 8 mm.

Wintering of third instar larvae takes place in bulbs, at a depth of five to eight centimeters in the soil, as well as in plant debris. Their development is restored in the spring, as soon as the average daily soil temperature reaches seven to eight degrees at a depth of five centimeters. In the steppe and forest-steppe of Russia, the flight of flies starts in the first or second decade of May, and in the Crimea it can be observed already at the end of April. For mating and subsequent laying of eggs, harmful flies need additional feeding on pollen and nectar. The periods of summer and egg-laying are somewhat extended in time. Eggs by pests are laid in small groups (from three to ten pieces) or one by one on leaves, necks and scales of plants, as well as under earthen lumps located near the bulbs. Each female easily lays up to hundreds of eggs.

Harmful larvae develop, eating away the tissue of the bulbs, as a result of which the latter rot, and the yellowed leaves wither. There are often groups of up to thirty larvae per bulb. Especially willingly parasites inhabit vegetation affected by other pests or various diseases. The development of eggs, depending on temperature, takes from five to ten days, larvae - from fourteen to twenty-two, and pupae - on average up to ten. Accordingly, under very favorable conditions for the development of one generation, thirty days is quite enough.

On the territory of Russia, for each growing season, these enemies of the onion are capable of producing two generations. At the end of August, the larvae of the second generation begin to enter diapause. Their wintering takes place in the same state. Often, the larvae, along with the bulbs, end up in winter storage facilities, from where they subsequently move to the onion fields in the spring.

How to fight

Before planting the onion, the sets are soaked in potassium permanganate or in a solution of a special preparation to destroy the onion hoverfly. It is not recommended to plant onions in the same place. Every four days, it is useful to loosen the soil around the bulbs - pests really do not like to lay eggs on loose soil. And after planting onions, the soil is mulched with rotted manure, peat or chopped spruce branches.

To accelerate the growth of onions, you can use urea - just one tablespoon is taken for one bucket. Three liters of the resulting solution will be more than enough for one square meter.

Planting carrots next to onions is a good solution - the carrot smell is good at repelling pests. During the flowering period of rose hips and cherries, onion plantings are weekly pollinated with tobacco dust, ash, ground pepper, mothballs or lime.

After harvesting, the onion should be thoroughly dried in an air stream, the temperature of which reaches forty - forty-five degrees. This procedure is carried out for ten to twelve hours. All bulbs are also carefully sorted before storage. It is equally important to observe the optimal storage regimes for garlic and onions. And after harvesting, the soil should be well shed with a solution of copper sulfate. Also, with the help of autumn digging of the soil, you can destroy part of the larvae of the gluttonous onion hoverfly.

Sulfur gas is sometimes used to protect against the larvae of these parasites, but such treatment will be most appropriate in large storage facilities. If the onion beds are badly damaged by hoverflies, then five grams of granulated basudin are added for each square meter.