Reproduction of Arion lusitanicus Mabille was studied in the field, in a region of the slug's mass occurrence, and in laboratory, at temperatures of 10, 15, 20 and 25°C. Places of egg-laying, fecundity and development rate were determined. In the field, A. lusitanicus mated in the third decade of July and started laying eggs early in August. The eggs were laid in clutches on or in the soil. In horticultural and agricultural crops the slug laid the most numerous eggs on field edges and baulks. An individual egg production was ca. 400, from 5 to 190 eggs per clutch. The first juveniles hatched at the end of October. In laboratory a close correlation was found between the duration of incubation period and the percentage of hatched eggs. The incubation period was the shortest at 20°C, the mean percentage of hatched eggs being the highest at 15°C. No eggs hatched at 25°C.
The Significance of Alien and Invasive Slug Species for Plant Communities in AgrocenosesThis paper lists alien invasive species of slugs occurring on crops grown in the ground and under covers, as well as in adjacent habitats. It gives a description of their origin, distribution within Poland, frequency of occurrence in different habitats, and an evaluation of the danger to cultivated plants posed by particular slug species. Based on reports in the literature and the results of original research, basic data is presented concerning the biology and harmfulness of these slugs on crops. The potential risk of the spreading of invasive slug species is evaluated, as well as their adverse impact on crop plants. It has been concluded that a major risk to the biodiversity of agrocenoses and to cultivated plants is currently posed by the slugsArion lusitanicus, A. rufusandA. distinctus. These slugs are spreading rapidly within Poland, often occur in large numbers, and do significant damage to various species of plant.
Palatability of 20 plant species to the slugs Deroceras reticulatum (O. F. Müller), Arion lusitanicusMabille and Arion rufus (Linnaeus) was estimated in laboratory food tests (multiple-choice and no-choice). The rate and degree of damage to seedlings and leaves of weeds, herbs and winter oilseed rape were determined, and plant species preferred or rejected by particular slug species were identified. Brassica napus and Datura stramonium were preferred by all the examined slugs, while Geranium robertianum was rejected. The slug species differed in their preferences for the remaining plant species.KEY WORDS: D. reticulatum, A. lusitanicus, A. rufus, weeds, herbs, winter oilseed rape, food preference, acceptability, palatability INTRODUCTIONPolyphagous slugs of the families Agriolimacidae and Arionidae are pests of agricultural crops and have a wide range of food sources (CHATFIELD 1976, BARRAT et al. 1994, GLEN et al. 1993. Besides arable and vegetable crops, they damage weeds, cultivated herbs and ornamental plants. Particular slug species have specific food preferences. Slugs readily feed on some plant species and completely ignore others (DIRZO 1980, MOLGAARD 1986, COOK et al. 1996, 1997, BRINER & FRANK 1998, KOZ£OWSKI & KOZ£OWSKA 2000, 2003. Knowledge about palatability of particular plant species to slugs is indispensable in studies on alternative pest control methods in arable crops. The pertinent studies concern the use of different weed species as alternative food for slugs (COOK et al. 1997, FRANK & FRIEDLI 1999 and the application of plant extracts or chemical plant compounds for the purpose of reducing pest feeding on arable crops (WEBBE & LAMBERT 1983, MOLGAARD 1986, BRINER & FRANK 1998, BARONE & FRANK 1999. Understanding feeding behaviour of slugs and their reaction to different plant species are prerequisites to such studies. This paper presents the results of studies on the preference for and acceptability of weed, herb species and winter oilseed rape chosen by the slugs, which attack arable crops in Poland. MATERIAL AND METHODSFood choice tests (multiple-choice and no-choice) were carried out on 20 plant species under laboratory conditions (day temperature 19°C, night temperature 16°C, RH 93%, day length 15 h).
The distribution of Arion lusitanicus Mabille and the damage caused by the slug were studied in 1993-2009. A total of 38 sites were examined, characterised in terms of location, time of appearance and density of the slug, type and size of crops affected, and degree of damage to plants. At the start of the 1990s A. lusitanicus occurred only around Rzeszów and in the Sub-Carpathian region. In 1997 it started to appear in other regions of Poland. The rate of its spread was found to have increased significantly, particularly in the past few years. The slug mainly colonises urban areas (30 sites), and much less often -other areas (8 sites). The slug densities were the greatest in cultivations. The degree of damage done by the slug varied among plant species. Brassicas, lettuce, beetroot, carrots, beans, strawberries, numerous ornamental flower plants and some weeds were the most damaged. The increase in the spread of A. lusitanicus poses a serious threat to the biodiversity of native habitats and to garden-cultivated plants.
The slugs Arion lusitanicus and Arion rufus inhabit ecologically degraded areas and are serious vegetation pests. In recent years, new localities of these species have been found in various parts of Poland. Here we study the morphology of 90 specimens from 9 populations of slugs. The morphology of the genital system allowed for the identification of 60 A. lusitanicus specimens from 6 populations and 30 A. rufus individuals from another 3 localities. In order to describe their genetic diversity at the level of the individual, population, and species, we compared sequences of the mitochondrial cytochrome oxidase subunit I (cox1) gene. The morphological analysis revealed that each of the studied populations comprised a single species, which was also confirmed by the molecular assay. We obtained 674-bp sequences of the cox1 gene for each species that showed a total of eight haplotypes. The genetic diversity of A. lusitanicus individuals ranged from 0.5% to 2.1%, whereas that of A. rufus was twice as low: 0.4-1.0%. The difference between the two species within the cox1 gene was at the level of 12%. Three A. lusitanicus and two A. rufus populations were found to be monomorphic. Large inter-population variability was found within each of the studied species, which suggests that the Polish populations of A. lusitanicus may have originated from repeated, separate introductions arriving from various parts of Europe.
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