Swedish fly on winter wheat

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Swedish fly on winter wheat shoots!

Swedish flies – oat ( Oscinellafrit L.) and barley ( O. Pusilla Meig.) belong to the widespread genus Oscinella and are dangerous pests of cereal crops. Oat and barley swedish flies are difficult to distinguish in both the adult and larval phases.

Swedish flies develop during the growing season in 2-5 generations, depending on local conditions. The entire annual development cycle of swedish flies, due to the absence of diapause, is a continuous successive change of different generations during the growing season.

The flies overwinter in the larval or puparia phase inside the host plant. The flies emerge sexually mature in the spring, but the maturation of the eggs requires additional feeding on flowering plants or grass apiaries.

One generation develops in about 30 to 50 days, depending on weather conditions.

Swedish flies lay their eggs on young plants, which are mainly in the phase of 2-3 leaves. The bulk of the eggs are placed on lumps of soil near the coleoptile, behind the coleoptile and the sheath of the first leaf.

The larvae of these flies lead a hidden lifestyle, they live inside plants. Damage caused by these species to plants from germination to tillering under unfavorable conditions for plant development causes thinning of crops and often leads to their death. Surviving plants have reduced yields and reduced grain quality.

The nature of the damage . The main most detrimental type of damage is the destruction of the growth cone in the seedling phase, causing the death of the stem (generalized damage to seedlings). External signs of damage are wilting and yellowing of the central leaf. If the main shoot and other productive shoots are damaged, as a rule, unproductive shoots are formed from the tillering node, which affects the size and quality of the crop. In one stalk of grain cereals, as a rule, only one larva belonging to one or another species lives.

Control measures. Of the active protective measures in the fight against grass flies, the use of insecticides is of the greatest importance. It must be remembered that they provide effective protection of grain crops from cereal flies during treatments only in the most vulnerable period of their colonization by pests. As the works of many researchers show, such a period in cereal crops can be considered two phases – germination and tillering, which, as a rule, coincide with the mass summer of flies and their laying of eggs. Treatments in the later phases of plant development do not give results.

The economic threshold of harmfulness in the phases of seedlings – tillering – 3-5 flies per 10 strokes of the net or 5-10% of damaged stems

Craft E.V., Gongalo A.A.
Researchers of
the field crops department of the Federal State
Budgetary Scientific Institution “Research Institute of Agriculture of Crimea”

In the world fauna there is a wide variety of flies. According to the latest data, there are more than 750 thousand species. Almost all of them harm a person in one way or another. One of these malicious pests is the swedish fly, a representative of the Chloropidae family. The insect quickly adapts to new climatic conditions and has spread throughout the globe.

The fly is not afraid of either cold or drought and can be found everywhere where cereal crops are cultivated or wild cereals grow. The insect painlessly endures a week-long hunger and is capable of long-distance migrations.

Biological features of the swedish fly

The first to describe the swedish fly was Carl Linnaeus, a famous naturalist and taxonomist. About 30 species of this pest are known, which are distinguished by food addictions.

The swedish fly cannot boast of a colorful color. She looks inconspicuous and it is quite difficult to distinguish her from her “brothers”.

The most harmful in our latitudes are 2 types:

  • The barley fly is an insect well adapted to drought. For laying offspring, it prefers barley stalks, which is reflected in the name. Also, this type of Swedish fly infects corn, wheat.
  • Oat fly – taste preferences are displayed in the title. The pest is localized on oat crops. The insect tolerates low temperatures well, loves humidity.

For a long period, barley and oat fly were systematized as one species.

How to recognize a swedish fly

For adults, the following features are characteristic:

  • the length of the black shiny body is 1.5-2.5 mm;
  • halteres, tarsi yellow;
  • wings are transparent with iridescent overflow;
  • a small proboscis and black antennae are located on a neat rounded head;
  • scutellum rounded, dorsum slightly convex, smooth without any dents or depressions;
  • sexual dimorphism is manifested by a different structure of the genitals.
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Elongated cylindrical eggs of milky or caramel color. Grooves are visible on the shell. The tiny size of the egg does not exceed 0.8 mm.

What does a larva look like?

  • The hatched larva of the Swedish fly is white, transparent. As they grow older, the color of the calf acquires a yellowish, lemon hue.
  • The body is cylindrical, divided into thirteen segments. From the back side it is smoothly rounded, tapering towards the tail and stands out with a sharp shape.
  • Spines are located on each segment, with the help of which the young individual moves.
  • The head is almost invisible. The oral cavity is represented by sickle-shaped serrated hooks, the color of which changes from light brown to black with the growth of the larva.

Pupation occurs in a brown cylindrical puparia. At the posterior end, two processes are visible, in front there are 4 cloves.

On a note! Grass flies are classified as hidden stem flies, since the larvae inhabit the stems of cereal seedlings.

Features of nutrition and life

The insect spends the winter period in the larval stage, or in the pupal stage, which is reliably protected from frost by the puparium. Individuals are found inside the shoots of wild cereals and winter crops, in carrion. In spring, when the soil layer warms up to a temperature of 12-14°C, the larvae come to life, begin to feed intensively and pupate. Young swedish flies appear on winter wheat and other shoots of spring crops during the tillering period.

The years of the first generation of barley and oat flies begin in late April, early May and are predetermined by geographical location.

On a note! According to the observations of farmers, the emergence of flies coincides with the beginning of flowering of apple trees.

The adult diet consists mainly of flowering plants. The main source of food for them is the nectar of flowers. Swedish flies have been seen on flowers of buckwheat, colza, anise, lupine, vetch, dandelion, yarrow, and valerian officinalis. According to some reports, the insect and aphids do not bypass their attention, which fills the need for protein.

The life expectancy of swedish flies depends on meteorological conditions, diet. Without food, they can live no more than 7 days. Under ideal laboratory conditions, receiving honey syrup, adults live up to 49 days. In the field, life expectancy is much shorter and does not exceed 28 days.

It is noteworthy that Swedish flies like to populate well-lit and sun-warmed places with low-growing cereal vegetation.

reproduction

10-30 days after leaving the cocoon, sexually mature individuals begin to mate. Females have an instinct for caring for offspring. The female scrupulously examines the plant in which oviposition will be carried out, because the development of the larva and the population as a whole largely depends on this. She looks for young shoots, strokes and taps them with her antennae, as if testing for strength and reliability.

Only young stems are suitable for laying eggs. Crops in the second leaf phase are predominantly infected. Less commonly, the insect lays offspring on plants with 4 leaves. Stems with more than 5 leaves are not considered by barley and oat flies. On winter wheat, swedish flies in hot weather can lay eggs even after the appearance of the first leaf.

Embryos are placed on the stems or germinal film of the entrances and almost never on the leaf itself. During the heading period of grain crops, the eggs are located in the spikelet film. Swedish flies are attracted to corn crops only in the 1-3 leaf phase.

On a note! During the season, 5 generations of generations are possible, which, depending on the time of appearance, populate stems, ears, crop residues, shoots of winter crops.

Embryonic development lasts from 3 to 8 days. The optimum temperature is 21-22°C. With a decrease in temperature, development slows down. The hatched larvae bite into the stem and begin to feed intensively. They are not particularly mobile and lead a rather secretive lifestyle. Swedish fly larvae go through 3 maturations, after which they pass into the stage of pupation. In summer individuals, the process takes place in the same plant in which they fed.

Maliciousness and methods

The mass settlement of swedish flies on cereal crops can bring serious losses to the owner of agricultural land. The harmfulness of insects depends on the time of their appearance, the intensity of settlement, the choice of a place on the plant for oviposition, as well as related weather conditions. The last generation of flies cause the greatest harm.

The pest of swedish flies is manifested in the following:

  • growth retardation of young seedlings, shoots, sometimes even their death;
  • stem thickening, expansion of leaf blades;
  • yield reduction;
  • if damaged during trumpeting, the affected stem becomes thinner, curved;
  • The appearance of the swedish fly on corn during the germination period leads to the fact that the larvae eat the growth cone and the seedlings die.

Measures to combat barley and oat fly are reduced to the following activities:

  1. Deep plowing of the soil.
  2. Selection of resistant varieties of cereals.
  3. Sowing works in optimum early terms.
  4. Application of fertilizers to fields with winter crops.
  5. Timely stubble peeling.
  6. In case of mass infection, insecticide treatment is carried out.

In total, insect pests, which are representatives of cereal flies, in Ukraine there are more than one hundred and twenty different species. These are, as a rule, small insects with well-developed wings and proboscis. The body color of grass fly species is usually dark, black, gray or yellow.

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The pest feeds, as a rule, on flowers (usually these are plants of the cruciferous, umbelliferous, euphorbia families), and lays its eggs in the sheaths of the leaves of cereal crops.

There are three main groups of flies – pests:

All cereal flies are classified as “hidden stem flies”. By “hidden-stem” insects, it is customary to mean a species group of cereal flies, the larvae of which settle in the stems of grain seedlings.

The most harmful are the following flies of the family: oat, barley ( also called swedish fly). This species also includes green-eyed, Hessian, wheat, spring and winter flies.

As a rule, the larva of a cereal fly inhabits one cereal (with the exception of the Hessian fly, in which many voracious larvae can settle on one stem).

Swedish fly (lat. Chloropidae).

Under the general name “Swedish fly” two related species are combined

– Oat fly ( lat. Oscinella )

– Barley fly ( lat. O. pusilla Meig )

The oat fly is about two millimeters long. Wings with a metallic sheen. The head is rounded with a proboscis. During one season, a fly generation can be updated up to five times!

The pest most intensively infects barley, oats, wheat (spring and winter), corn, and other cereals, however, based on the name, it prefers to infect fields sown with oats most of all.

For laying, the female chooses seedlings with a pair of developed leaves. In the axils of these leaves, the fly lays its egg.

After about a week, a voracious larva (reaching two to three millimeters in length) emerges from the egg.

The larva is light yellow in color, has a cylindrical body.

The pest gnaws a recess in the stem of a growing cereal and then, through the hole made, enters the plant, where it begins to feed on the delicate juicy tissues of green oats.

The larva leads a secretive way of life (hence the name of the group “hidden stems”).

It contains original salivary glands, which, by releasing a special enzyme, allow it, for better digestibility, to break down the plant fibers of the plant

When the central stem is damaged, the cereal usually dies, and yield losses can be more than forty percent. The larva also feeds on unripened grains, which significantly affects the decrease in grain yield.

The swedish fly overwinters in the larval phase in stems, carrion, on wild cereals.

An adult swedish fly has an excellent sense of smell, therefore it determines the field of cereals it needs by smell.

The barley fly is more adapted to dry conditions and additionally feeds on flowers. The color of the insect is black, the abdomen is yellowish shiny, the legs are painted yellow. The size of the body is about two millimeters in length

For laying eggs, it prefers barley seedlings (hence the name of the insect).

The egg is oval, white, up to one millimeter in size. About a week later, a larva appears from it, which also penetrates into the middle of the stem, where it settles and begins to feed on the central leaves of the plant, which is why the cereal most often dies.

Green- eyed ( lat. Chlorops pumilionis Bjerk ) is widespread and widespread. Develops in two generations.

The fly and larva infect about eighteen species of cultivated and wild cereals. The pest is especially not indifferent to barley and spring wheat. In autumn it damages winter seedlings.

The body of the fly is up to five millimeters long and is painted in combinations of yellow and black. On the back, clearly drawn longitudinal lines are visible.

The eggs of the pest are white, oblong. Each is about one millimeter long.

The larva is white or light yellow, cylindrical in shape, reaches nine millimeters in length.

Like the larvae of other representatives of cereal flies, the green-eyed larva penetrates the stem of the cereal crop, where it lives, feeds, and then pupates.

The stems affected by the pest are shortened, the cereal is not eared or is partially eared

When damaged by larvae, spring wheat can lose up to fifty percent of its yield.

Wheat fly – ( lat. Fhorbia floralis Meig ) is the main pest in the company of “hidden stem” insects. Develop in two generations.

Under dry weather conditions, it can damage up to ninety percent of spring wheat, resulting in a high mortality rate for cereals. Distributed everywhere. Damages wheat (spring and winter), sometimes barley.

In length, the insect grows up to five millimeters. The life cycle of development (adult insect – egg – larva – adult insect) is similar to the life cycle of the swedish fly.

The egg is white, about a millimeter long. The fly lays an egg in the vagina of the first young leaves. The development of the egg lasts from two days to a week, then a white or yellowish (about eight millimeters long) larva appears from it.

The larva penetrates the stem and gnaws out a passage to the embryo of the ear, feeding on the succulent tissues of the plant along the way. Due to damage, the main sheet turns yellow and dries. The shoot infected with the pest most often dies.

Flies of the second generation lay their eggs on seedlings of winter wheat. The hatched larvae pupate while being directly on the grass.

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Hessian fly ( lat. Mayetiola destructor Say ) severely damages winter and spring wheat, barley. Develops in three generations.

It looks like a small mosquito, red or brown. Paws are long, reddish.

The female is darker, has a red stripe and several dots on the belly.

The egg is transparent, half a millimeter in size.

The larva has two instars. At the first age, the pinkish or yellowish larva has a worm-like shape (up to one millimeter long). At the second age, it becomes like a spindle and acquires a milky or slightly greenish hue of the body. Grows up to five millimeters in length.

A damaged cereal, after a larva has started in it, either dies (with an early damage) or does not ripen and gives a poor grain yield (with a later damage).

The female lives for about a week and, unlike the Swedish fly, lays not one, but many eggs (up to eighty, but usually thirty – forty). The eggs are placed on the upper side of the leaf blade of the cereal, which is why the laying looks like a small chain.

The embryo develops for about a week, after which it turns into a larva that feeds on the juices of the plant, inhibiting the growth and development of the stem. Ears of cereals damaged by a pest become as if trampled down, or as if they were beaten by hail.

In a warm and humid climate, four to five generations of the Hessian fly develop.

The spring fly ( lat. Phorbia genitalis ) is widespread throughout Ukraine.

It damages winter and spring wheat, barley, and other cereal crops.

The fly has a length of up to four to five centimeters. The body is black, the abdomen is gray, there is a velvety dark coating all over the body. Paws are black. Wings with black or dark brown veins.

The egg of the fly is white, a little more than a millimeter in size, with the end bent on one side.

The fly lays an egg on the leaf sheath, where, after about a week, an insatiable larva is born, which, like other Swedish fly larvae, gnaws a hole through which it penetrates the stem and lives inside the plant, making moves inside the cereal. The central leaf of the plant turns yellow and dries up, which in most cases leads to the death of the ear.

Pupation occurs either in the plant itself or near it

Winter fly – ( Delia (Leptohylemia ) coarctata Fll) damages wheat (winter), spring crops and wild cereals. Develops in one generation.

Insect up to a centimeter long. The body is reddish or yellowish-gray in color with large black setae.

Cream larva. Winters on winter crops. In the spring, it emerges from the egg and penetrates into the young sprout of winter wheat. The larva can crawl from one stem to another, thus damaging three to five seedlings. It eats away the central leaf of the cereal, causing it to turn yellow and dry out.

Under favorable conditions, it can destroy up to sixty percent of the grain crop.

Ways to deal with grass flies

Calibration of grains before sowing and the selection of the most varietal seeds gives stable and strong seedlings that are able to resist the pest and are damaged to a much lesser extent.

The introduction of balanced mineral fertilizers in the presence of good soil moisture contributes to the early growth of seedlings, and accelerates the ripening of cereals, which is why they are less susceptible to damage, because they coarsen and become unsuitable for feeding by fly larvae earlier.

For prevention, it is advisable to place crops with grain crops after legumes or tilled crops. The best predecessor for sowing cereals is bare fallow.

To reduce the level of infestation, it is necessary to carry out a sowing campaign as early as possible, then the cereals have time to survive the critical phase of colonization by fly larvae.

Careful post-harvest work is also important, such as stubble breaking and early deep plowing, which should be carried out to a depth of at least twenty-two centimeters. High-quality autumn plowing is capable of destroying a colony of cereal fly larvae on stubble and carrion.

Reduces the number of pests and timely stacking of straw.

Chemical methods of protection against grass flies

The insect harmfulness threshold is thirty to fifty flies per square meter.

Of the active means of protection, it is recommended to use insecticides by spraying. The most commonly used insecticides are neonicotinoids, which can provide long-term protection against pests.

Drugs such as Cruiser and Select Top are used.

Biological methods of combating the cereal fly

Predators (representatives of the order Hymenoptera, as well as ground beetles and arachnids and parasites) cause the greatest harm to the population of cereal flies. In total, there are up to forty different species that can harm the population of cereal flies.

To increase the effectiveness of entomophages, it is necessary to fight for an increase in their numbers. For this, it is desirable to sow nectar-bearing crops near the fields of cereals.

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