Ways of controlling the number and harmfulness of slugs

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Poltava State Agrarian University, Ukraine

Ways of controlling the number and harmfulness of slugs

Nechiporenko Natalia Ivanivna

Candidate of Agricultural Sciences, associate professor

Pospielova Ganna Dmytrivna

Candidate of Agricultural Sciences, associate professor

Pospielov Sergii Viktorovych

Doctor of Agricultural Sciences, Professor

Head of V.I. Sazanov Department of Agriculture and Agrochemistry

Summary

slug harmful biological

Based on the analysis of literary sources, basic information on the morphological and biological characteristics of slugs is given, and the species composition of the most common and harmful species of slugs on the territory of Ukraine is described. The characteristic of their damage to cultivated plants and the main methods of controlling their number are summarized.

Key words: slugs, Agriolimacidae, Limacidae, Arionidae, harmfulness of slugs, methods of control, medicinal herbs, horticultures, phytophages.

Analytical analysis of literary sources shows that usually the zones of constant harmfulness of slugs in Ukraine are regions characterized by a regime of high humidity, namely: Polissia, Volyn, Zakarpattia, Peredkarpattia, Western Forest- Steppe, but recently the problem has become more and more common in the Central Forest-Steppe as well [1,9]. This is primarily due to the fact that slugs prefer moist loamy soils and are not found on sandy soils [10]. In addition, more and more favorable conditions are created due to the change in climatic conditions. There is also information about the growth of slug populations in the years of a sharp rise in solar activity and in the initial phase of its decline [1].

Phytophagous slugs belong to an order Stylommalophora [5]. From the family of Agriolimacidae, the most harmful species are: field slug (Agriolimax (Deroceras) agrestis L.), grey garden slug (A. reticulatus Mull.), marsh slug (A. laevis Mull).

A representative of Limacidae family is great grey slug (Limax maximum L.), which is present in the park biocenoses of Kyiv and Lviv, as well as in Prykarpattia.

Arionidae family includes rather harmful species: orange-banded arion (Arion fasciatus Nilss.), brown-banded arion (A. circumscriptus Johnst.), dusky slug (A. subfuscus Drap.).

The main pests of plants from Helicidaefamily are Roman (Helixpomatia L.) and white-lipped (Cepaea hortensis Mull.) snails [5].

According to the nature of nutrition, slugs can be omnivorous, carnivorous and herbivorous [5]. Some species of slugs are phytophages, inhabiting and damaging more than 140 types of plants [6, 8]. Currently, it is believed that slugs owe their fairly easy orientation to food sources exclusively to their fine sense of smell [10]. Previously, they were considered only pests of garden crops in open and closed soil, vineyards, fruit and berry crops, but currently their harmfulness is increasing on field crops (even on cereals), especially rape [2, 5]. Among vegetable crops in open soil, slugs prefer seedlings and adult plants of vegetable crops from a wide range of botanical families (cabbage, pumpkin, nightshade, celery, quinoa, legumes, etc.). Vegetables in closed soil in cultivation facilities of various types are also subject to damage. The type of damage caused by these phytophages can be characterized as "gross eating", since they often bite into the stems of seedlings of vegetable crops, and in the leaves they bite elongated holes, sometimes leaving only large veins, sometimes completely eating the plants. In the fruits of cucurbits, nightshade and leguminous crops, in the heads of cabbage, root crops and tubers, slugs eat significant cavities. A similar nature of damage is observed on berry and fruit crops, especially strawberries [1, 3-6, 10]. We have repeatedly observed damage to the aerial mass of medicinal plants Stevia rebaudiana Bertoni, Valeriana officinalis L., Mentha xpiperita, Melissa officinalis L.

In field agrocenoses, seedlings of winter crops, located next to tree and shrub plantations, are of particular interest of slugs. Field crops suffer somewhat less from them due to the non-coincidence of vulnerable phenophases of crops and periods of mass appearance of the harmful stage of slugs [1].

The nature of their harmfulness in all these cases leads to a decrease in the weight of the yield and a significant deterioration in its quality due to contamination with mucus and excrement. In addition, in the process of feeding these pests, infectious material of fungal and bacterial etiology enters the plant [1, 5-7, 9].

Currently, it has been established that in European conditions, vegetable, fruit and berry crops are harmed, first of all, by slugs from the order Stylomatophora. Phytophagous, first of all, are slugs of the genus Milax from family Milacidae (Milax gagates, M. budapestensis, M. sowerbii, M. nigricans), from family Arionidae (orange- banded arion - Arion fasciatus, A. ater, A. hortensis, A . rufus, A. lusitanicus), Deroceras and Limax from Limacidae family (grey garden slug - Deroceras reticulatum, field slug - D. areste, marsh slug - D. leave, Limax marginata, L. ventianus, great grey slug - L. maximus , cellar slug - L. flavus). Damage by snails of genera Cepaea and Bradybaena of Helicidae family (Cepaea hortensis, C. nemoralis, Bradybaena fruticum) is observed much less often, mainly on currant and raspberry fruits [10].

The greatest damage to field crops is caused by slugs of the genera Derocerasus and Arion, especially field slug (Derocerasus agrestis L.), grey garden slug (D. reticulatum Mull.), red slug (Arion rufus L.) and brown-banded arion (A. circumscriptus Johnst.), which do not form a shell. Among snails with shells, Roman snail (Helix pomatia L.) causes minor damage to grapes only on calcareous soils [2].

Slugs are very sensitive to drying out, so they damage plants mainly at night and in wet weather, hiding during the day in moist, cool and shady places, under plant remains and clods of soil, in soil cavities up to 10 cm deep, in basements and trenches. Opression and death of snails can be caused not only by intense solar radiation and high air temperatures, but also by a decrease in temperature to +4-7 °С. It is known, for example, that if necessary, in search of suitable conditions, some species of Arion can even migrate from the borders to the edge of fields, advancing 20-50 meters within 1 -2 days [2, 6].

It is believed that in European conditions, the most important natural enemy of slugs is Rain-Beetle (Pretostichus melenarius Illig), although in field agrocenoses, unlike vegetable plantations, slugs have relatively few natural enemies. A certain role in reducing the number of these phytophages is played by spiders and fly larvae that feed on eggs, as well as some species of birds and shrews [2]. In Ukraine, the most active natural enemies of slugs are caterpillar hunters (Calosoma), which also belong to family Corabidae [6].

Active universal monitoring of slugs is currently not carried out in Ukraine, but if necessary, European methodical technologies can be taken into account. In order to evaluate the population of slugs in agrocenoses in the European Union countries, special test films or jute bags soaked in beer, which are covered with a film, are used. 20-30 pellets of bait (metaldehyde-bait/0.25 m²) are placed in them. It is necessary to place several such traps on the field. In the morning, you can count slugs [2].

Morphological and biological features of slugs make it difficult to control their number and harmfulness. An effective solution to this problem requires a rational combination of effective agrotechnical methods under the condition of a high level of their implementation during the period of greatest vulnerability of slugs [1]. First of all, it is necessary to destroy the possibility of hiding places and places of concentration of slugs, such as: level the surface of the base from cracks and recesses, remove stones and lumps, post-harvest remains, containers, pegs, garbage, etc. from the areas. The basic agrotechnical measure in the system of plant protection against slugs is the quality of soil cultivation, due to which the periodic loosening of the plowed layer completely destroys hiding places and mechanical destruction of slugs at various stages of development. Weed control improves the limiting of feed base of slugs, most often in crops or on vegetable or berry plantations, as well as on field boundaries and between cultivation structures. All these measures also serve the regulation of humidity in herbaceous cultivated plants, which affects the conditions for the existence of slugs [1, 6, 8].

It is recommended to place vegetable and berry plantations in well-lit areas, avoiding low, overmoistened and sodden places. An important measure to regulate the humidity in the grass is also the observance of the density of plant standing on vegetable plantations and timely and high-quality thinning of berry trees [1,6, 7].

Exterminating measures for slugs are also developed and quite diverse. The most accessible and cheapest is dusting the places of concentration of slugs and the ways of their movement from hiding places to agricultural or decorative crops, as well as between rows on plantations with slaked lime or powdered superphosphate at the rate of 20-30 g/mT and 30-40 g/mT, respectively. These substances cause irritation of the integumentary tissues of slugs and the associated excessive secretion of mucus. That is why the covering of the soil with these substances must be constantly renewed in order to weaken and kill pests due to active mucus secretion [1,6].

Currently, the "List of pesticides and agrochemicals approved for use in Ukraine" (2020) and the supplements to it (2021) do not contain recommendations for the use of chemical and biological limacids.

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