Raspberry Beetle

2024 Author: Sebastian Paterson | [email protected]. Last modified: 2023-12-16 13:47

About the features of the development of the raspberry beetle on plants and how to combat this malicious pest

Collecting tender and juicy raspberries, probably, each of you had to, removing them from the fruit-bearing, find yellowish larvae of a raspberry beetle (1.5-7 mm in size and with a dark-colored head) in the fruits and casually throw them aside.

The raspberry beetle (Byturus tomentosus) is considered one of the most serious and ubiquitous pests of this crop, both in our gardens and in its wild thickets. Beetles are also found on blackberries, cloudberries, drupes, apples, cherries, pears, plums, mountain ash and other fruit and berry crops, as well as bird cherry. On the territory of the country, the beetle is most active in the European part, it is especially harmful in wet years.

The damage to the raspberry crop from the beetle and its larvae is, depending on the growing conditions, from 10 to 50%. The grayish-black body of the imago (elongated oval, 3.5-4.5 mm in size) is abundantly covered with rusty-yellow or gray hairs, which is why its color appears to be grayish-golden. The emergence of beetles from wintering on the soil surface occurs at the end of April - the first half of May at a temperature of its upper layer of 12 … 13 ° C. As a rule, this moment coincides with the flowering period of fruit trees and bird cherry.

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To achieve the ability to reproduce, beetles additionally (up to two weeks) feed on nectar and anthers of flowers of various cultural (currants, gooseberries, somewhat later apple trees, cherries) and early flowering weeds, and then fly to raspberry plantations (the flight distance reaches up to 120 m) … In some years, the colonization of raspberries by beetles begins early, even before the buds appear. Then, for additional nutrition, the beetles feed on young leaves of raspberry, plucking out the pulp of the tissue and gnawing narrow oblong holes between the veins.

With the appearance of buds and flowers, the imago feeds on them, biting into the buds or eating away the nectaries (to a lesser extent other parts) of the flowers. As experts note, when feeding on pollen of additional forage plants, the maturation of reproductive products in females is accelerated almost twice as compared to beetles that constantly feed on raspberry leaves and buds.

The female lays white or yellowish eggs of an elongated-elliptical shape, about 1 mm long (up to 20-30 eggs in total), one at a time between the stamens and pistils in the flowers and at the tops of the ovaries. The period of oviposition is extended, so beetles can be found on raspberry bushes for two months (their maximum number falls on the time of mass flowering of bushes), even at the time of ripening of berries. After 8-12 days, the larvae hatching from the eggs live for some time outside the fruit, and then bite inside, where they feed, making moves, with a fleshy receptacle of still forming green berries and the adjacent part of the drupes, often severely damaging the berries themselves. Such fruits develop poorly, shrink, become ugly, wither and often rot, especially in wet weather.

The maximum number of damaged berries is observed during the period of their collection; such fruits not only lose their nutritional quality, but also reduce the yield. The larvae live in raspberries for up to one and a half months, capturing the ripening period of the fruits, as a result of which they are often found in the harvested berries. During the ripening period of berries, the larvae leave them and burrow into the soil, where they pupate in cradles at a depth of 5-20 cm, later turning into hibernating immature beetles. If beetles emerge from pupae by the wintering period, they, as a rule, die with the onset of frost. Some of the late developmental and matured larvae enter a state of prolonged diapause, as a result of which such larvae hibernate and pupate.

Beetles of a new generation appear only in August next year, i.e. in a year. Recall that diapause is a specific state of an insect, when when unfavorable soil and climatic conditions occur for its further life, its biological processes are reduced to a minimum, and mechanisms of resistance to these negative environmental factors are activated in the body. The number of diapausing larvae varies from year to year within 10-82% of the total number of wintering individuals: the later the larvae hatch and feed, the more of them remain for wintering. The depth and location of the larvae depend mainly on the structure of the soil and its moisture. It turns out that under certain soil and climatic conditions, the raspberry beetle can have a two-year development period.

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When harvesting raspberries, you will notice that the caterpillars often remain in the berries and can only come out after some time. If you put cheesecloth or other dense material in the container where the raspberries are collected, you can collect and destroy the majority of the beetle larvae that have accumulated there. I often practiced this method: after the bulkhead, before making the jam, the berries were immersed in salt water, in which the larvae emerged from the damaged fruits, and thus freed from them.

Of the agrotechnical measures that significantly reduce the number of wintering beetles and larvae, the most common practice is to dig the soil under the bushes. Some of the owners of household plots, during the budding of raspberries, use open umbrellas or containers with wide necks (for example, pots) to collect and destroy beetles, where they are shaken off. This procedure is best carried out in the morning, when the beetles are the least mobile, do not "get on the wing", flying from bush to bush: this method can catch more than half of the insects. Damaged berries with larvae should be systematically removed and destroyed, and not just thrown aside, since the hit of the larvae on the ground often leads to their pupation (especially if they are older and managed to feed on the fruits).

Chemical treatment against the raspberry beetle can be directed simultaneously against the raspberry-strawberry weevil, flower beetle weevil, leafworms, aphids and other accompanying raspberry pests that colonize this crop during the period of bud formation.

Of insecticides, fufanon, Kemifos, Iskra M (10 ml), Iskra (1 tab.), As well as actellik (15 ml) are used (per 10 liters of water). Preparations of the first group are used at the rate of up to 2 liters per 10 bushes, and actellik - 1.5 liters per 10 m², keeping the waiting period recommended by the instructions before picking berries.