Rapeseed leaf beetle - pest of cruciferous crops

Leaf beetles beetles are one of the largest families, including 35 thousand species. They are common around the world except Antarctica. The main food of imago and larvae is plant leaves. Some species are used by humans to combat the proliferation of weeds. In addition to useful insects, the family includes the worst enemies of crops - Colorado beetles. Among the pests of crops includes rapeseed leaf beetle. He specializes in cruciferous plants - cabbage, radish, swede, rape, mustard and other plants.

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Rapeseed beetle (Entomoscelisadonidis) - an insect of the order Coleoptera, family leaf beetles. The body of the beetle is oval with convex elytra. Size 7-10 mm, males are smaller than females. Coloring is bright - red-yellow with a distinct pattern. On the scutum of the pronotum, the broad median and two lateral spots are black. Three longitudinal black stripes pass along the elytra - two on the sides and one along the seam.

Interesting fact. A characteristic feature of leaf beetles is the ability to draw paws and antennae under the body so that they are not visible from the side.

The head is covered with a single capsule passing into the prothorax. The eyes are rounded. Antennae are distinct, composed of 11 segments, directed forward. The mouth organs of the gnawing type, the jaws are adapted for grinding plant food. The upper lip, clypeus and crown are black. The apical angles of the pronotum are rounded, and the elytra are rectangular. The lower body and limbs are painted black.
Elytra covered with rows of punctures. Under them are well-developed wings used for flying. Rapeseed leaf beetle wings are transparent with pronounced venation.

The abdomen, completely hidden by the elytra, consists of 5 sternites and 6-8 tergites. Legs are walking type. The coxae of the fore and middle extremities are fixed movably. The foot is widened and flattened, with a lot of hairs on the sole. Flattened tibia with one noticeable spur.

Distribution area

Species Entomoscelisadonidis lives in regions with a mild climate. Beetles are found in the southern part of Western Europe, Asia Minor, Kazakhstan, Mongolia, and northern China. Insects brought to North America. In Russia, they live in the Caucasus, southern Siberia.

Lifestyle & Reproduction

Beetles are found in dry areas of the forest-steppe and steppe zones, mountain areas at the height of alpine meadows. Rapeseed leaf beetle lives openly on fodder plants, disturbed adults fall to the ground. One of the worst enemies of the insect are riders and tahini flies that parasitize on larvae. At high humidity, up to 18% of the offspring are affected.

In the beginning of summer, imagoes crawl out of the soil. They feed on flowers and cruciferous leaves. They are not ready for reproduction and need additional nutrition, which lasts about two weeks. In the hottest period of summer, beetles begin diapause. Insects stop feeding and burrow into the soil to a depth of 15-20 cm. Imago return to activity in late August or early September. The breeding season begins. At this time, the beetles feed on cabbage pods, eat up seeds.Leaf beetles fly well, with the deterioration of the conditions for the existence of adults develop new territories. After breeding, the beetles die.

Breeding

Females lay reddish-brown oval eggs in the topsoil. Their length is 1-2 mm, the number is 150-280 pieces. Eggs hibernate in the soil, but offspring have time to emerge from the lingering warm autumn. In this case, larvae of the first age are sent for wintering. Usually, larvae hatch in early spring, in April. Their bodies are elongated, spindle-shaped.

Initially, the color is yellow, after molting, the upper part becomes dark brown or black, and the lower part is ocher-yellow. Body length 14-15 mm. On each segment there are several warts with hairs. A large head and three pairs of limbs are black. Development takes 10 to 28 days. Larvae succeed four ages. When the temperature drops below 10 °, they burrow into the soil.

Information. Adults and leaf larvae have a protective mechanism. In case of danger, they emit an unpleasantly odorous caustic substance.

Imago damage winter rape, cabbage seedlings. In ordinary years, the damage is negligible. The species is dangerous in the south of European regions of Russia, where in favorable conditions most of the offspring survive. The larvae are inactive, they do not creep far from the place where the eggs were laid. At the end of May, they dig into the soil to a depth of 6-10 cm, where they pupate in an earthen cradle. Pupa red-black, 10 mm in size. The pupal stage lasts 8–10 days. If the air temperature is below 20-22 °, it is delayed up to 20 days.

Malware

Young larvae feed on cruciferous weeds - shepherd’s bag, wild mustard, brisk field. If there are agricultural crops of cabbage and oilseeds nearby, they are moved to them. Pests during outbreaks of mass reproduction pose a particular threat to the crop. Beetles eat the flesh of leaves, leaving only veins, flowers and cruciferous pods. Prefer to eat cabbage, rutabaga, mustard, radish and canola.

Information. Depending on the region, 1-2 generations of rapeseed leaf beetle develops per year.

Ways to deal with rapeseed leaf beetle

If a mass invasion of red-black beetles is detected on the site, the question arises, how to deal with canola leaf beetle? Pests are destroyed by physical methods and chemicals.

Physical and agricultural activities

To protect cabbage crops from damage, the following steps must be taken:

1. Timely destroy weeds on the site. Wild cruciferous crops are the food base of pests.
2. Autumn plowing of the soil, carried out after laying eggs by females of rapeseed leaf beetle.
3. Summer loosening of the soil near cabbage crops and between rows helps to remove pests from the soil and destroy the pupae.
4. On a small individual site, manual collection of adults and leaf beetle larvae provides high efficiency. Collected bugs are destroyed.
5. Early planting of cruciferous seedlings is recommended.
6. One of the tricks of farmers is the planting of small sections of rapeseed, distracting leaf beetles from the main crop.

Chemical treatment

When more than 5-6 adult individuals are found on a single plant, insecticide treatment is indispensable. Agricultural fields are pollinated with 12% dust of hexachloran in a dosage of 10-20 kg per 1 ha. This is a powder of white or gray color, which is a poison of contact action. Also used are solutions of insecticides: Phobecid, Karbofos, Zollon, Actellik, Metaphos. Processing is performed in the evening, when insects sit on the tops of the leaves.

Contact and intestinal contact chemicals enter the body of beetles with food. For several hours, they cause paralysis, disrupt the functioning of enzymes and the transmission of insect nerve impulses. The protective effect of insecticides lasts 2-3 weeks.