Why is the Swedish fly dangerous on winter wheat and how to deal with it and other cereal pests

What kind of pest is this

The Swedish fly is a member of the family of cereal flies Chloropidae (order Diptera) . It was first described in Sweden by the first taxonomist Carl Linnaeus (1756). About 30 species of this insect are now known.

What does it look like

The adult has an elongated body measuring 1.5-2.5 mm and black in color . The female's abdomen is thicker and ends with a narrow ovipositor. The scutellum is rounded, the dorsum is slightly convex and smooth.

The wings are small transparent with a metallic sheen. On the head there is a small proboscis and black antennae.

Why is it dangerous for winter wheat?

The Swedish fly causes the main damage to winter wheat in the fall . Emerging at the end of September, the females lay eggs in the leaf axils of young shoots during the period when the second leaf emerges. Then egg laying stops and usually stops after 50% of the third leaf has reached.

The hatched voracious larvae, which are twice the size of an adult, penetrate the shoots at the base of the stem. There they eat upward, reaching the ear bud, and eat it and the milk grains.

If the Swedish fly larvae damage the main stem, the crop dies , which is why the yield percentage is significantly reduced - by 50%.

Reference! Swedish fly larvae damage about 20 species of cultivated and 46 species of wild cereals.

Reproduction and life cycle

Pests reproduce so quickly that in one season they manage to produce up to 5 generations of individuals if the weather is favorable. The female carefully chooses a suitable place. First, it checks all the stems, stroking them with its antennae, and then lays eggs in cereal plants that have reached a certain stage of the growing season. The size of the eggs is 0.7-0.8 mm.

The larvae develop within the egg for approximately eight days , then emerge in search of food. With the help of special salivary glands that secrete a specific enzyme for the breakdown of plant tissue, the rudiments of future wheat grains are absorbed.

In nature, the life cycle of larvae is about a month with sufficient nutrition, in laboratory conditions - up to 40 days. They can survive without food for a maximum of seven days.

The insect spends the winter hibernating as a pupa in the stubble of perennial cereals and on the seedlings of winter crops. Activates with the arrival of spring at temperatures above +12°C.

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Swedish fly - a pest of grain crops

Swedish fly

(Osinosoma frit L.) is a dangerous pest of grain crops and forage grasses; it belongs to the family of cereal flies Chloropidae (order Diptera). It was first described in Sweden by the great taxonomist Linnaeus (1756).

The fly is shiny black, 1.5-2 mm in size; the head is round, the proboscis is small with wide suckers, the antennae are black. Mesonotum slightly convex, without grooves or longitudinal stripes; the shield is rounded at the back. The wings are transparent with a metallic sheen, the marginal vein (castal) reaches the fourth longitudinal (medial). The legs are black, the abdomen is black, the female’s is thicker, ending in a narrow ovipositor.

Close view of O. pusilla Meig. differs in that the fore and middle tibiae are light, the hind tibiae are darkened in the middle; halteres with a light head. The length of the seta (arista) of the third antennal segment is longer than that of O. frit.

Many researchers have established feeding differences in these closely related species. O. frit is called the oat fly, which often breeds on oats (young stems and grains of milky ripeness), while O. pusilla is a barley fly, more common on barley, wheat, corn and many cereal grasses.

The egg of barley and oat flies is white, oblong, 0.7 mm long and 0.2 mm wide. The egg shell is covered with oblong grooves, which run almost parallel in the middle part and gradually merge at the ends; at the blunt end there is a funnel-shaped opening - the micropyle, through which the male sperm passes, fertilizing the egg.

The larva is white with a yellowish tint, transparent; body shape is cylindrical; the anterior end is thin, the posterior end is rounded, with two small cylindrical projections opening at the apex into spiracles. At the anterior end of the body, on the lower side of the third segment, there are anterior spiracles, which look like a fan of 5-6 respiratory tubes (the number is typical for this species). The head of the larva is not prominent; antennae short, two-segmented; the oral hooks are sickle-shaped, serrated, light brown in young larvae, later becoming black. The body of the larva consists of 13 clearly demarcated segments; at their boundaries there are small spines that aid in movement. Adult larvae are lemon yellow, 3-4 mm long, 0.4 mm wide.

The false cocoon is hard, yellow to brown; two protrusions are visible at the back, and four teeth at the front. The length of the false cocoon is 2-3 mm, width 1.3 mm; females are slightly larger in size than males.

Swedish fly: 1 - adult insect; 2 eggs; 3 - larva; 4 - false cocoon; 5 - damaged stems; 6 - damaged oat grain; 7 - damage to corn

The Swedish fly has significant adaptability to various environmental conditions, which has allowed it to spread unusually widely across the globe (most of Europe and Asia, North America, northern Africa). In Europe and Asia it is found from the White to the Mediterranean Sea and from the Atlantic to the Pacific Ocean. In the north of Europe it has spread to Arkhangelsk and even to Lapland, that is, it crosses the Arctic Circle. In Siberia it is distributed to the Amur and Ussuri regions. Recorded in Kolyma - in the permafrost region. It is also found in the extreme south of the Soviet Union in Georgia and Tajikistan, especially in irrigated grain crops.

The Swedish fly has settled where its food plants grow - cultivated and wild cereals. In the north, the spread is limited by low temperatures, in the south by exceptional dryness and heat.

Larvae of different ages overwinter in the stems of cereals and winter grains (usually in the third age). In warm autumn, some of the larvae pupate; in the spring, flies fly out of these false cocoons earlier. After the snow melts and the ground layer of air warms up to 12-14°C, the overwintered larvae come to life, begin to feed, then turn into a pupa and after a certain period the flies fly out. According to our observations, the appearance of flies coincides with the flowering of early varieties of apple trees. In the vicinity of Moscow, the appearance of the Swedish fly in the fields was noted between May 3 and June 8, most often on the twentieth of May.

The emergence of the Swedish fly in the Oryol region occurs in the first and second decades of May. At the Poltava experimental station, the appearance of the Swedish fly over 15 years was noted on average on May 4, with a deviation of up to 10 days. In the North Caucasus, the beginning of flight is observed earlier - at the end of April - beginning of May.

The lifespan of flies is related to nutrition and meteorological factors. In the insectarium of N.V. Andreeva, flies lived 33-39 days; in our experiments, flies fed on honey syrup lived 20-47 days, and flies fed on colza flowers lived 13-28 days. Without food, life lasts 2-3 days, maximum 7 days. The nectar of flowers of many plant species serves as food for flies. We had to mark flies on the flowers of buckwheat, vetch, lupine, rapeseed, anise, and bird buckwheat. The Swedish fly has a highly developed sense of smell, and it finds food by the smell of flowers. I.M. Zambin and A.I. Karpova (1940) note that flies are attracted to bedstraw, yarrow, dandelion, basil and valerian during the flowering period.

Apparently, in addition to the sugary substances found in nectar, the Swedish fly also feeds on protein foods. I have repeatedly observed a significant number of flies during the flowering period of these plants when mowing with a net on rye, oats, and bluegrass. In our experiments, flies that fed on pollen collected from the anthers of wheat and timothy lived for 19-22 days and laid eggs. I.M. Zambin and I.F. Pavlov established that food for flies can be “pasok” - the sweet secretions of the vegetative parts of cereal plants.

In field conditions, flies are found from spring to autumn and stay mainly in places with low grass vegetation, well lit and warmed by the sun.

In addition to wild, low-growing vegetation, the Swedish fly lives on cultivated cereals (spring and winter grains, forage grasses). During the growing season, flies migrate between cultivated and wild cereals, depending on the condition of the grass stand and the microclimate in it.

At the beginning of growth, spring grains are usually poorly colonized by the Swedish fly. With the onset of tillering, the number of flies on crops increases noticeably until the grass stand closes and the plants become tall. During the booting period, the number of flies decreases and reaches a minimum during heading, while on low grass vegetation near grain crops there are a lot of them. When oats bloom, flies appear here again and remain in noticeable numbers throughout the entire flowering period, after which they move to wild cereals.

The laying of mature eggs by a female on plants is one of the most important instincts - caring for offspring. It is very important to find a suitable plant in the appropriate phase of development and determine the place for laying the egg, which determines the development of the larva and the existence of the species itself as a whole. Obeying an innate reflex, the female looks for young stems of cereals and prepares to lay eggs. According to the observations of I.V. Andreeva, the female carefully examines the desired stem, strokes and taps it with her antennae on all sides. If the stem fits, it lays an egg on it.

The Swedish fly infects only young stems. The second leaf phase is most optimal for egg laying on spring grains; stems with four leaves are weakly infected; On stems with 5-6 leaves, egg laying does not occur. On early sowings of winter grains in hot weather, a lot of eggs are laid on seedlings in the first leaf phase. The Swedish fly, laying eggs on young stems, places them mainly behind the coleoptile, then on the stem and on the ground near the stem, very rarely on a leaf. On corn crops, the fly lays eggs on seedlings in the phase of 1-3 leaves, mainly behind the coleoptile.

In addition to the stems, the Swedish oat fly lays eggs during the period of knocking out oats and barley by the membrane of the spikelet. Upon emerging from the egg, the larva feeds on grain in milky ripeness. Egg development takes an average of 3-8 days. According to N.N. Troitsky, at a temperature of 18 °C, egg development lasted 8-12 days, at 22 °C - 4-8 days.

Research by I.D. Shapiro (1969) established that Swedish fly larvae have large salivary glands that secrete enzymes that dissolve delicate plant tissue. This carries out extraintestinal preparation of food, as a result of which the larva finds itself among a liquefied, highly nutritious food substrate. Liquid food enters the stomach through a very narrow esophagus, where it is further chemically processed and then absorbed.

Many researchers have detected significant mortality of larvae on corn. Corn “self-cleaning” of the pest occurs: the larvae are carried out of the plant during the growth of the stem and the protrusion of leaves.

The larva goes through three instars during its life. The colorless and transparent larva that has just emerged from the egg is 1 mm in length, after 4-6 days it molts and enters the second instar, in which it lives for 4-6 days and reaches a length of 1.5-2.3 mm; shedding for the second time. In the third instar, development takes 10-16 days, the larva becomes yellow, the mouth hooks become black, the number of teeth increases to 4-5, and the body length reaches 2.5-4.5 mm.

The life of a larva is closely related to temperature. Observations by E. A. Kreiter in a polythermostat established that at temperatures below 6°C the larvae are motionless, at 7°C weak movement begins, and at 10-12°C more active. The larvae begin feeding when the ambient temperature is at least 12-14 °C.

In summer, the lifespan of the larvae is 18-28 days. Before pupation, the larva becomes almost motionless and does not shed its last skin. Later, the skin hardens, turns brown, and a barrel-shaped false cocoon is formed.

The pupal phase lasts 11-25 days. The formed fly, with the help of the head bladder, breaks through the wall of the false cocoon and comes out; after an hour, the head bladder is retracted, the wings straighten and harden, and the fly becomes capable of flight. The complete metamorphosis of the Swedish fly lasts 32-59 days at the latitude of Leningrad, 28-30 days in the forest-steppe zone of the Ukrainian SSR, and 25-30 days in the South-East.

The duration of the development cycle of the Swedish fly depends mainly on temperature conditions, which requires the following sum of effective temperatures (with a development threshold of 10 ° C): for the egg 43-46 °, larva 140-157 °, pupa 139-143 °; only 322-346°. According to I.V. Kozhanchikov’s definition, a full development cycle requires 400° (with a lower development threshold of 8°C).

In the southern zones of the USSR, where the warm period is much longer and the sum of effective temperatures is higher, more generations of the Swedish fly can go through (up to five) than in the northern regions (2-3). However, the number of generations depends not only on temperature, but also on humidity, amount of precipitation, and the presence of food plants.

In the steppe regions, due to drought and the lack of young succulent stems, 1-2 generations fall out in the summer. In the northern regions of the non-chernozem zone, due to lack of heat, no more than three generations develop, and in cold rainy summers - only two. In the central regions of this zone, three generations were noted: the first in spring on spring grains, the second in summer on spikelets of oats and barley, the third on wild cereals and shoots of winter grains.

In the South-East there are three main generations per year, and in the irrigated farms of the Volga region - four.

Our research has established that in cold summers with an average daily temperature of 15.2°C, half as many prostrates are deposited on plants as in hot summers. The size of the autumn generation depends entirely on the weather conditions in August and September. With the early onset of cold weather, egg laying stops. On the other hand, too high temperatures and drought in the summer cause a food crisis: wild grains dry out and the larvae are left without food. Cereal plants grow well and bush in wet weather, so precipitation in July and August determines their development and the reproduction of the Swedish fly. According to our observations over a 16-year period (1935-1939, 1945-1955), two years were noted (1938-1939) with a minimum amount of precipitation in July-August of 10.4-38.6 (long-term average 354.0 mm ), which caused a sharp decrease in the number of the autumn generation of the Swedish fly and slight damage to spring grains by the spring generation of the next year. In severe winters with little snow, many larvae die during overwintering.

Parasitic insects limit the reproduction of the Swedish fly by 10-20%, rarely by 50%. Over 16 species from the order Hymenoptera parasites of the larvae and pupae of the Swedish fly have been identified. The two most common species are Rhoptomeris eucera Htg. and Trichomalus cristatus Foerst. Parasitic nematodes belonging to the species Tylenchinema oscinellae Goodey develop in the abdomen of the Swedish fly. They castrate the ovaries and testes, causing the flies to become infertile.

External parasites include the red mite Microtrombidium demeijerey Oudums. Under the wings of the Swedish fly, mites attach themselves to the abdomen, thereby preventing the development of the ovaries. The importance of nematodes and mites in reducing the number of Swedish flies is small.

Analysis of the stems of winter grains and wild cereals in late autumn (October) and early spring after the snow melts shows the age composition of overwintering larvae, their death over the winter and makes it possible to make a forecast about the expected number of Swedish flies on spring grains.

For a short-term forecast of the beginning of the appearance of flies in the spring, you can focus on the flowering of early varieties of apple trees. Daily mowing with a net at 12-13 o'clock in the afternoon (in light winds) on winter and wild cereals makes it possible to determine the beginning of the emergence of the Swedish fly. The timing of flies' emergence should be determined from false cocoons collected in glass tubes. The ends of the tubes are plugged with cotton wool and placed in moistened sand. The count of emerging flies is carried out in the morning. At the same time, parasites are also taken into account. Autopsy of females gives an idea of ​​the development of the ovaries and the consumption of the fat body; These characteristics can be used to determine the age of oviparous females.

By taking into account the damageability of spring grains and by the results of mowing with a net on wild cereals near spring wheat, barley and oats (at the beginning of the emergence of second-generation flies), one can assume the intensity of colonization of winter crop seedlings by the Swedish fly.

By the beginning of the emergence of seedlings, it is advisable to perform an autopsy of the females, to clarify their maturity and the possibility of laying eggs (by the development of the ovaries and the amount of fat body).

The infectivity of winter crops in August-September is mainly determined by the temperature during this period. Egg laying stops when the daytime temperature drops to 10-11 °C.

The Swedish fly larva lives inside the lower etiolated part of the young stem, near the tillering node. It feeds on delicate embryonic tissues, but the tillering node and axillary buds are usually not damaged. When opening a damaged stem, you can see how the entire etiolated part has been eaten away by the larva.

Damage to growing tissues stops the growth of the stem: the diseased stem remains in the phase of development at which the damage occurred. Due to damage to its lower part, the central leaf withers and turns yellow. The result is a characteristic type of damage to the young stem: the central leaf is yellow, the rest are green. Typically, the external picture of damage (yellowing of the leaf) is revealed on the 8-16th day from the start of feeding of the larvae. Sometimes the damaged leaf is missing: it either falls off or does not come out of the leaf sheath.

Plant tolerance to damage to main stems and lateral stems varies. When the main stem is damaged, the plant reacts differently than when the lateral stems are damaged: the yield sharply decreases or the plant dies due to a lack of growth factors or early damage.

Resistance to damage increases noticeably as the plant ages. The most dangerous thing for a young plant is damage to the main stem in the second leaf phase. According to our records, 27-63% of spring wheat seedlings died, and when damaged in the third leaf phase - 2 times less. According to L.V. Znamensky (1934), in the conditions of the left bank of Ukraine, up to 55% of winter wheat died, and up to 35% of rye plants were damaged in the main stem.

Under favorable conditions of nutrition and humidity, the plant damaged in the main stem does not die, but begins to bush. At first, such a plant looks much weaker than neighboring healthy ones. It can be easily identified by its low growth and delay in heading of healthy lateral stems. In the conditions of the Moscow region, it can be assumed that the loss of spring wheat grain yield from damage to the main stem of an undead plant averages 50% (harm factor) compared to a healthy plant.

Damage to the lateral (secondary) stems does not cause such drastic changes as to the main stem. First of all, the plant does not die and in appearance differs little from a healthy one. Comparing the yield of plants damaged in lateral stems with the yield of healthy ones with equal tillering, in spring wheat, when one stem died, the grain loss (harm factor) was 13-26%, and from two - 33-41%.

In timely early sowings of spring grains, the lateral (secondary) stems are more affected than the main ones, and in the fall, in the seedlings of rye and winter wheat, mainly the main stems are affected. The appearance of secondary stems occurs later, and when the autumn cold snap occurs, they are not damaged.

Corn shows a different type of damage. With early infection, when the growth cone is destroyed by the larva, the seedlings die. If the axillary buds are intact, side shoots - stepsons - begin to develop. For the most part, the larvae do not reach the growth cone; they gnaw through 5-7 thin etiolated leaves rolled into a tube. Subsequently, when the damaged leaves begin to unfold, tears characteristic of the Swedish fly form on them. When seedlings are damaged and growth energy is weak, 3-14% of plants die, 10-18%, 32%.

When leaves are damaged, the harmfulness coefficient depends on the intensity of the damage, as well as on the variety and agricultural technology. According to the definition of P. G. Chesnokov, in weakly resistant varieties of corn the harmfulness coefficient is 40-74%, in varieties with high resistance - 8%. According to V.A. Megalov, damaged plants that have formed stepchildren reduce the yield by 54%. In the Leningrad region, L. M. Lisina determined a decrease in the weight of plants with weak eating of leaves by 2-26%, and with early damage (the central stem dies, the plants form stepchildren) - by 84-91%. Research by I. F. Pavlov, L. M. Kozhevnikova, V. A. Megalov, and I. D. Shapiro has established that corn plants damaged by the Swedish fly are more susceptible to smut infection.

In addition to young stalks of corn, cereals and wild cereals, the Swedish (oat) fly damages oat and barley grains in milky ripeness. In soft grain, the larva eats through the grooves, wears it out, as a result, the grain becomes puny, lightweight, and loses its germination capacity.

According to our long-term data, a decrease in the yield of spring grain in the conditions of the Moscow region occurs from damage to secondary (lateral) stems. When sowing is early, the infestation of the main stems does not exceed 10%. Of the total bushiness, the Swedish fly destroys 20-40% of the stems in spring wheat, 30-50% in barley, and 25-40% in oats. Annual grain harvest losses average: spring wheat 12%, barley 15%, oats 11%. Every year, 40-70% of plants in spring grain crops are damaged.

In irrigated fields of the Altai Territory, crop losses from the Swedish fly amount to 11%. In the Saratov region, in some years, damage to the main stems of spring wheat reaches 30-50%, which causes the death of plants in the crops by 10-35%.

According to the Accounting and Forecasting Service, damage to the main stems of spring grain crops reaches 20%, in some cases - 40-60%. In early sowings of winter wheat and rye, seedlings are damaged by 50-80% in hot weather. The damage rate of oat grains in 1964 was 0.5-8%, and in 1965 - 0.3-10%, in 1968 - 1-24% (maximum 54%), in 1969 - up to 14 %. Barley grains are less damaged. According to our records in the Moscow region in 1955-1961, the damage to corn plants was in the range of 20-55%. In many farms in the central regions of the non-chernozem zone of the BSSR and the Baltic states, 20-50% of damaged plants were noted. According to the generalized data of I.D. Shapiro (1962), in the forest-steppe zone of the European part of the USSR, the damage rate of corn plants is 25-50%, in the steppe zone - 5-20%, in the Urals - 5-15%, in Western Siberia and Northern Kazakhstan - no more than 15-20%.

G. M. Ignatovich and G. L. Mokrievich, who examined corn crops in the Rostov and Novocherkassk regions, established plant damage up to 30%. According to P. I. Susidko and M. D. Bienko (1969), the damage rate of corn reached 50% in the Dnepropetrovsk region, 83% in the Kyiv region, and 40-83% in the Odessa region.

Control measures

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Agrotechnical measures
. Deep autumn plowing, carried out in a timely manner, destroys larvae and cocoons on stubble and carrion. In the steppe zone of the European part of the USSR, where the Swedish fly develops most intensively on carrion seedlings, early deep plowing reduces the main supply of pests.

Spring grains sown in a timely and well-made plowed field develop better and become more resistant to damage by the Swedish fly.

Fertilizers increase plant vigor and development, which helps cereals resist damage from the Swedish fly.

The timing of sowing spring and winter grains is of exceptional importance in protecting seedlings from the Swedish fly. In early sowings of spring grains, the main stems and partly the secondary stems are less damaged. This is due to the fact that by the beginning of the mass appearance of the Swedish fly and its prostrate laying, the plants emerge from the critical phase of infection into the main stem and by this time have 4-5 leaves. In addition, cold weather is more common in early spring, which reduces the infestation of crops. For corn, early optimal sowing dates are also of great importance in effective protection against Swedish fly.

If in the spring the dynamics of egg laying on spring crops constantly increases, then in the autumn on seedlings of winter crops it decreases every day depending on the decrease in temperature. On crops in the first half of August, seedlings of winter wheat and rye in the Moscow region are severely damaged by the Swedish fly (36-94%); at optimal sowing dates (August 20-30) - less than 4-10%; in warm weather at the end of August, stem damage increases to 30-50%. Crops on September 5 are not affected at all, but they give a low yield.

According to eight-year experiments by I. F. Pavlov (1942-1949), in the Penza region, damage to winter crop stems was noted in crops in the first half of August within the range of 13-43%, and in crops at the end of August - 2-8%.

The sowing dates for winter crops recommended by scientific institutions as the most productive for a particular area will also be acceptable from the point of view of protecting seedlings from the Swedish fly.

Resistant varieties. Those varieties that have high growth and tillering energy and rapid development of mechanical tissues in the stems are more resistant to damage by the Swedish fly.

Of the barley varieties, they stand out for their comparative resistance - Evropeum 353/133, Pallidum 18, Odessky 09, Kharkovsky 305. Yellow grain oats are more resistant to the Swedish fly than white grain ones. Relatively resistant yellow-grain oats include Zolotoy Dozhd, Lokhovsky, Lishevetsky, etc. Increased damage by the Swedish fly to durum wheat varieties has been noted: approximately 2 times more than soft ones.

Among the varieties and hybrids of corn, two forms are clearly distinguished: late-ripening and early-ripening. Moreover, late-ripening hybrids have high growth energy, produce the highest yield of green mass and are more resistant to the Swedish fly. These include the hybrid Bukovinsky 3, Voronezhskaya 80, VIR-42, Sterling, etc. Tooth corn is more stable compared to flint corn.

Chemical method

. In case of mass emergence of the Swedish fly, pollination with 12% hexachlorane dust provides high technical and economic efficiency. According to our long-term data (1949-1969), pollination of spring grains at the beginning of tillering with a hexachlorane consumption of 10-15 kg per 1 ha reduced the number of Swedish flies by 66-93%, and damage to stems by 70%; the yield increase was 20%. Pollination of winter crops in the first leaf phase with 12% hexachlorane dust (8-40 kg per 1 ha) protects crops from severe damage.

Aeronautical spraying of barley and oat crops with hexachlorane (8 kg per 1 ha), carried out by the Belarusian Institute of Agriculture on Peat Soils, gave an increase in yield of 7-9 centners per 1 ha.

To protect corn seedlings, dusting with hexachlorane at a rate of 10-15 kg per 1 ha during the period from emergence (awl) to four leaves is effective; this period lasts 6-8 days. Conducted by us in 1955-1961. A single spraying of industrial corn crops with hexachlorane ensured a reduction in plant damage from 24-40 to 2-11% in the Moscow region; in the Kaluga region from 53 to 6%, in the Gorky region from 52 to 4%.

Spraying crops with organochlorine and organophosphorus preparations is also effective; The number of Swedish flies is significantly reduced, resulting in reduced damage to plants.

In our tests of spraying barley, oats and spring wheat at the beginning of tillering, stem damage decreased from 22-30% (control) from a 4% hexachlorane suspension to 3-7%. from chlorophos (0.2%) to 8-10%, phosphamide (0.2%) to 8-9%. With a decrease in the number of damaged stems, productive bushiness increased by 13-30%.

In order to save working time and fuel, it is more advisable to carry out complex spraying simultaneously against weeds and Swedish flies. At the beginning of tillering of spring grain crops, and on corn in the phase of 1-3 leaves, the crops are colonized by flies, and at this time full shoots of weeds are noted. Carrying out complex spraying during such a period is effective. In autumn, on winter crops, complex spraying should be carried out in the phase of 1-2 leaves.

Our research on the combined use of herbicides and insecticides has been ongoing since 1951; The following most effective preparations and their consumption rates per hectare were identified: chlorophos 1 - 1.5 kg per 1 ha; 16% emulsion concentrate of the gamma isomer HCH 1 kg per 1 ha; suspension of 12% hexachlorane 10 kg per 1 ha with the addition of amine salt 1.5 kg per 1 ha.

When processing crops, tractor sprayers are used, consuming 150-200 liters of working fluid per hectare. Over four years of our studies of complex spraying of spring wheat with sodium salt 2,4-D with hexachlorane, a decrease in damage by the Swedish fly was noted by 60-88% - from 24-45% (in the control) to 5-12% of damaged stems. The infestation of crops decreased 10 times.

Spraying barley with chlorophos (1.5 kg per 1 ha) or a suspension of hexachlorane with herbicide reduced the damage to stems from 30% (control) to 3-6%; the number of ears of corn in the crop increased by 16-25%, the increase in grain yield was 9-12%. At the Mari Agricultural Experiment Station, complex spraying of barley and oats in 1966-1967. reduced the damage to stems from 10-18 to 3-4% and ensured the death of weeds by 79-96%. The wheat grain yield increased by 27-30%, oats - by 30-55%. The increase in grain from the use of herbicides was 1.3-4.9 centners per 1 ha, from chlorophos or hexachlorane - 1.4-3.0 centners per 1 ha. At the Ryazan Agricultural Experimental Station, complex spraying of barley with amine salt 1.2 kg per 1 ha, hexachlorane 10 kg per 1 ha, urea 4 kg per 1 ha gave a yield increase of 3 kg per 1 ha.

Effective complex spraying from airplanes and helicopters. In four-year (1964-1967) joint experiments of the All-Union Institute of Agricultural Aviation and the Research Institute of Agriculture of the Non-Black Earth Zone on spraying barley at the beginning of tillering (main stem 3-4 leaves) with chlorophos 1.5 kg per 1 ha and amine salt 1 .5 kg per 1 ha with a working fluid consumption of 25-50 liters per 1 ha, a decrease in the damage to stems by the Swedish fly was noted by 68-84%, and weed death by 70-99%. The increase in barley yield is determined at 3-5 quintals of grain per 1 hectare, with the cost of work and chemicals being 3 rubles. for 1 hectare.

Corn seedlings need chemical protection from Swedish flies and weeds. Experiences from scientific institutions show the high efficiency of the complex chemical method. Conducted by us in 1960-1962. Spraying corn seedlings in the second leaf phase with a 4% suspension of hexachlorane mixed with 2,4-D herbicides reduced the damage to plants from 23-40 to 2-5% and ensured that the crops were free from weeds.

For 4 years (1960-1963), we studied pre-emergence spraying of corn (1-3 days before emergence) with simazine (3 kg per 1 ha) with the addition of 12% hexachlorane (10-15 kg per 1 ha) . There was a complete absence of weeds during the growing season and a good protective effect against the Swedish fly - plant damage did not exceed 6% (22-30% in the control).

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Reasons for appearance

The main reason for its widespread appearance is the ability to adapt to different climates . There are other factors that contribute to the spread of the population on winter wheat:

1. Long warm autumn . The period of pest activity increases (at a temperature of +10°C, the insect already goes into hibernation).
2. Aridity . Dry weather promotes active growth and development of larvae.
3. Nutritional conditions for the growth of winter crops. The more food that enters the plant, the stronger it is, and the stages of development occur much faster. Consequently, the Swedish fly’s period of eating the plant is reduced, since it causes damage at a certain phase of the crop’s growing season.
4. Favorable temperature for the period of larval growth (above +10 °C).
5. The ability of an insect to migrate over long distances.

Symptoms of the lesion

First of all, the larvae influence the development of the stem . The central leaf withers and turns yellow, sometimes it is completely absent: it either falls off or does not come out of the leaf sinus. External signs of damage caused by the Swedish fly appear approximately two weeks after the larvae settle.

The plant tries to direct forces to the damaged areas, so the color of the leaves becomes intense green and the stems thicken. Using this feature, specialists accurately determine the presence of the Swedish fly in wheat fields.

Reproduction

During the season, the population of the Swedish fly can be updated up to 5 times.

The most interesting moment of reproduction is the laying of eggs by the female, because an important ritual of this action is the choice of a future home for the larvae.

The plant in which the eggs will be laid must be in a suitable phase of development,

therefore, the female carefully examines the stems, stroking and knocking on them with her antennae. Usually her choice is on shoots with two developed leaves, in the axils of which she lays white eggs reaching 7 mm in length. The duration of development of the larvae inside the egg does not exceed 7-8 days; the emerging larvae bite into the stem and subsequently feed on the rudiments of future grains until they harden.

An interesting fact is that the mandibles of the larvae are supplemented with salivary glands, which secrete a special enzyme that breaks down plant tissue.

Fighting methods

The damage caused by insects can be significantly reduced with the correct choice of means of combating it.

Agrotechnical

The most effective ways:

1. Maintaining crop rotation . The best predecessors: legumes (clover, alfalfa, peas, soybeans, vetch-oat mixture), corn, annual grasses except sorghum and Sudan grass. It is not advisable to sow wheat on one plot for more than two years.
2. Selection of stable seed material with strong fiber that protects the ear from damage by larvae.
3. Sowing late varieties (for example, Mirostan, Chaus, Krasnodol) at the optimal time so that winter crops begin to rise with the onset of frosts, when flies hibernate.
4. Increasing the grain sowing rate, so that out of the number of sprouted ears, most of them survive and the harvest remains at the same level.
5. Deep plowing of the soil.
6. Application of nitrogen fertilizers to fields with winter crops to increase plant viability.

Chemical

During the egg-laying and mass summer periods, chemical treatment of wheat is carried out . Using aviation, winter crops are pollinated when their development is in the first leaf phase. In many areas, 12% hexachlorane dust is widely used.

The population of harmful insects is reduced when plants are sprayed with organochlorine and organophosphorus agents. Insecticidal preparations are also used, for example, “Cruiser” and “Celest Top”.

Attention! The death of the fly after treatment reaches 93%, the yield increases by 20% or more.

Chemical control measures

It is important to use both seed treatment with an insecticidal protectant and treatment with insecticides during the growing season. The main effective method, which plant protection specialist Eduard Eduardovich Shevela advises to use, is treatment with fungicides (with one, two, three components according to the active ingredients) with the addition of an insecticidal preparation. Treating seeds is practically the most important stage of the fight, since at this stage we protect seeds and seedlings from a complex of diseases and a number of pests.

Today, a key role in the fight against grain flies is played by the use of insecticidal treatments based on neonicotinoids - thiamethoxam and imidacloprid, registered for seed treatment. Due to the presence of systemic activity, these drugs can reliably protect plants from fly larvae, reducing the number of Swedish and wheat fly larvae by 76-100%, and damage to productive stems by 79-95.8%.

At the same time, these insecticides reduce the number of dangerous pests such as striped flea beetle (Phyllotretavittula Redt.) and ground beetle (Zabrustenebrioides Goeze.) by 86-100%. It is also important that with this method of application, insecticides are safe for entomophagous cereal flies and other types of insects. This increases the protective effect of the treatments performed.

It is equally important during the period of mass flight of cereal flies (several species can be found on crops at the same time), when their total number is above the economic threshold of harmfulness (EPV = 30 flies per 100 sweeps of the net), to carry out chemical treatments with insecticides. The list of drugs approved for use in the Russian Federation in 2013 includes more than 30 drugs based on 11 active ingredients of domestic and foreign production - from the chemical classes of organophosphorus compounds, pyrethroids and neonicotinoids.

Insecticidal treatments during the growing season should be applied mainly by spraying. It must be remembered that they provide effective protection of grain crops from grain flies when carrying out treatments only during the most vulnerable period of pest infestation. As the work of many researchers shows, such a period in cereal crops can be considered two phases - germination (1-2 leaves) and tillering, which, as a rule, coincide with the mass flight of flies and their laying of eggs. The most important thing is to prevent the larva from descending down the stem and pupating. Treatments in later phases of plant development do not produce results.

Preventive measures

To obtain a high yield, preventive measures are necessary:

1. Timely peeling of stubble to destroy the pest and its larvae.
2. Sowing with high-grade calibrated seeds. They produce friendly and strong shoots, and these are more resistant to the attacks of the Swedish fly.
3. Treating grains before sowing into the soil. The drugs “Gaucho” and “Cruiser” are used.
4. crops with grain crops after legumes or row crops.

Winter fly

Damages wheat (winter), spring crops and wild cereals. Develops in one generation. An insect up to a centimeter long. The body is red or yellowish-gray with large black bristles.

The larva is cream colored. Overwinters on winter crops. In the spring it emerges from the egg and penetrates the young sprout of winter wheat. The larva can crawl from one stem to another, thus damaging from 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.

Other pests of winter wheat in seeds, plantings and warehouses

The number of cereal pests is very large. Let's talk about those causing the greatest harm.

bug turtle

The insect prefers to feed mainly on wheat, damaging crops of both winter and spring crops . Externally it looks like a tiny turtle. The development cycle of the bug is directly related to the growing season of cereals, so throughout the entire summer period the turtle leads an active lifestyle, causing significant damage both in the fields and in storage facilities.

bug turtle

Trips

Wheat thrips damages winter and spring wheat , as well as some cereal perennial grasses. Both adults and larvae are harmful. The insect feeds on fresh juice from the spike scales or from a young succulent leaf, as a result of which the cereal stops growing.

The grains in the ear receive severe damage - they become chipped and defective, which affects the overall quality of the seed. Externally, thrips is a small black-brown fly with poorly developed wings and a size of 1.3-1.5 mm.

Wheat thrips

Ground beetle

The bread ground beetle causes the greatest damage to winter wheat . The larvae of this pest begin their activity during the period of rising and beginning of tillering of seedlings. They eat leaves and young stems, turning wheat bushes into soaked fiber. Adult beetles infect the ears. They gnaw the scales of the ear, the rudiments of the grains, and gnaw out the ripening grains.

The insect size is 12-17 mm, color is pitch black with a bronze tint . The head is large, the antennae are short, the elytra are convex with deep punctate grooves.

Ground beetle

Weevil

The beetle's mouthparts are an elongated proboscis . With its help, the insect destroys the dense skin of grain or cereal. The weevil is considered one of the main and most dangerous pests of grain crops - wheat, barley, buckwheat, corn, as well as pasta; it destroys stocks both in the kitchen and in huge grain storage facilities.

The insect has an elongated body measuring about 4 mm, dark brown, almost black in color . If it has wings, it is not adapted for flight, but it moves long distances on ships and trains carrying industrial batches of grain.

Weevil

Balance of power

According to the Federal State Budgetary Institution "Rosselkhoztsentr" for the Volgograd region, in the last three years there has been a tendency to increase the number and harmfulness of grain flies on winter and spring grain crops. In the autumn of 2012, a significant wintering stock of grain flies was identified. According to the control spring survey of 2013, the overwintering of the pests was satisfactory, the death of larvae did not exceed 15%. The flight of grain flies of the overwintered generation on winter grains has been recorded in the southern regions of the Volgograd region since April 15 with intensity ranging from weak to strong.

The colonization of cereal flies was detected on 66% of the surveyed area (in 2012, 48% of the surveyed area) with an average number of 21 individuals. per 100 strokes of a net (15 copies per 100 strokes – 2012).

In most areas this year, the number of cereal flies in winter crops was higher than last year. In a number of Southern, Central and Northwestern regions of the Volgograd region, a high number of flies was noted, in Surovikinsky - 50 specimens. per 100 sweeps of the net, Kalachevsky - 56 copies. per 100 swings of the net, Svetloyarsk region - 40 copies. per 100 swings of the net, Frolovsky - 45 copies. per 100 swings of the net, Serafimovichsky - 85 copies. for 100 swings of the net.

Warm weather with precipitation in the second half of April was favorable for the breeding of grain flies. The hatching of larvae began at the end of the month. The number of fly larvae per 1 m2 was higher than last year, especially the Hessian fly larvae; it varied from 16 to 118 individuals/m2. The harmfulness of the larvae was registered on 40% (in 2012 27%) of the surveyed area with damage to an average of 9.6% (2012 2.8%) of the stems; in some fields in the Frolovsky district it amounted to 24% of the stems, in the Surovikinsky district - 14% of the stems , Serafimovichsky district - 12% of stems, in Kotelnikovsky district - 30-80% of stems.

The colonization of spring grain crops was observed in the 1st decade of May. Swedish and black wheat flies predominated in barley crops. The flight intensity ranged from 20 – 30 specimens. per 100 net strokes (in 2012, 2 – 13 specimens per 100 net strokes). On average, stem damage amounted to 4.9% (in 2012, stem damage was 1.1%).

In the third ten days of May, mass pupation of cereal fly larvae was observed. Summer weather conditions in most of the territory of the Volgograd region have developed satisfactorily for the development and reproduction of this pest.

After harvesting winter and spring crops, the bulk of the puparia of the Hessian fly remained in the stubble, from where the flies will fly to the seedlings of winter crops. Flight of the second generation of flies is expected in the second half of August. In warm weather in September-October (daytime air temperatures above 10°C), an extended period of flight for imago cereal flies and active colonization of winter crop seedlings is predicted. Cereal flies lay eggs on winter crops, starting from the phase of 1-2 leaves - it is this period that requires maximum attention when monitoring the number of pests.

How to deal with wheat pests

Measures to combat the listed pests and preventive procedures are carried out approximately the same and include:

1. Agrotechnical measures : stubble peeling and deep fall plowing, compliance with crop rotation and sowing dates, growing resistant varieties.
2. Chemical : spraying grain with approved types of insecticides, for example, “Karate”, “Arrivo”, “Fastak”, “Aktelik”.
3. Preventative : before storing in storage, treat grain with agents based on carbendazim, mancozeb, triticonazole. And also maximum drying of the product, thorough cleaning of the room, disinfection of the storage, for example, with formaldehyde vapor (after this, the storage is kept hermetically sealed for 2-3 days, then thoroughly ventilated).