Monika Jaskulska

Analysis of studies of the effectiveness of a biological method of protection for organic crops

SUMMARY As a result of intensive changes in plant production and of environmental changes in agrocenoses, certain agrophages, such as slugs, have in recent years been causing ever increasing amounts of damage to crops of agricultural, horticultural and orchard plants. As a result of the European Parliament and Council Directive adopted on 13 January 2009, the countries of Europe have been required to implement integrated plant protection. One of the principles of this protection is the implementation of strategies which minimize the use of chemical pesticides. Moreover, in accordance with decisions of the European Commission, many active substances have been or are to be withdrawn from the list of available pesticides. An example is metaldehyde, which is to be withdrawn from use in EU countries in the next few years (Commission Decision C/2008/7637 of 5 December 2008). It therefore becomes necessary to seek environmentally safe substances and to develop non-chemical methods for protecting plants against harmful slugs. An alternative to chemical molluscicides is the parasitic nematode Phasmarhabditis hermaphrodita. Studies have been made of the effectiveness of this biological method in combating Polish populations of the invasive slug species Arion lusitanicus. This was an incomplete multivariate study, i.e. not all variables could be observed for all treatments on all experimental units. Multivariate model of observations has been derived and a method of analysis has been described. The results of these studies provide a basis for the development of environmentally friendly methods of protecting plants against harmful slugs.

The role of alkaloids in the feeding behaviour of slugs (Gastropoda: Stylommatophora) as pests of narrow-leafed lupin plants

ABSTRACT The degree of damage done to lupin plants by slugs is highly dependent on the species and the cultivar of plant. A study was carried out, in laboratory conditions and on small plots, to investigate the extent of damage done to plants of eight cultivars of narrow-leafed lupin when exposed to grazing by Arion vulgaris, Arion rufus and Deroceras reticulatum. Five sweet and three bitter cultivars of lupin were selected, respectively, having low- and high-alkaloid content. The contents of the dominant lupine alkaloids in these plants were determined. It was found that the susceptibility of the plants to slug damage is dependent on their content of alkaloids. The plants of high-alkaloid cultivars (Karo, Mirela and Oskar) were less heavily damaged by the studied species of slugs. The greatest differences were recorded for A. vulgaris and D. reticulatum, while the differences for A. rufus were smaller. For all studied slug species, the differences were statistically significant. The results of carried out experiments may potentially be of use in the selection of cultivars of Lupinus angustifolius to be grown in areas inhabited by these slug species.

Shell colour, temperature, (micro)habitat structure and predator pressure affect the behaviour of Cepaea nemoralis

Although shell colour polymorphism of the land snail Cepaea nemoralis is a well-known phenomenon, proximate and ultimate factors driving its evolution remain uncertain. Polymorphic species show variation in behavioural responses to selective forces. Therefore, we estimated effects of various environmental factors (temperature, humidity, food availability, (micro)habitat structure and predatory pressure) on behavioural response (frequency of locomotion, climbing and hiding) of C. nemoralis morphs, in experimental and natural conditions. In the experimental part of study, the frequency of locomotion was negatively affected by temperature and the presence of food and positively influenced by the presence of light. Morphs significantly differed in behavioural responses to environmental variability. Pink mid-banded and yellow five-banded morphs climbed less often and hide in shelter more often than yellow and pink unbanded individuals when temperature was low and food was absent. Snails fed most often at moderate temperature compared to low and high temperatures. Field investigations partially confirmed differences among morphs in frequency of climbing, but not in terms of probability of hiding in sheltered sites. In natural colonies, temperature and (micro)habitat structure significantly affected frequency of climbing as well as hiding in shelter. Snails more often hid in sheltered sites where thrushes preyed on Cepaea. Tendency of unbanded morphs to climb trees may have evolved under avian predatory pressure as thrushes forage on a ground. Tendency of banded morphs to hide in sheltered sites may reflect prey preferences for cryptic background. The results implicate that differential behaviour of C. nemoralis morphs compensate for their morphological and physiological limitations of adaptation to habitat.

Evaluation of damages caused by slugs (Gastropoda: Arionidae, Agriolimacidae) to selected agricultural plantsOcena uszkodzeń wybranych roślin rolniczych powodowanychprzez ślimaki nagie (Gastropoda: Arionidae, Agriolimacidae)

Slugs present a serious threat to many species of cultivated plants. Recently, more damage has been observed in minor crops, mainly Fabaceae family. In order to investigate of plants from this family susceptibility to various species of slugs, we performed laboratory tests assessing the degree of damage caused by Arion vulgaris, Arion rufus and Deroceras reticulatum to six plant species. We determined the extent of plant damage during seven days of slug grazing in no-choice tests. Significant differences were found among the plant and slug species included in the study. Common vetch and serradella were more susceptible to damage caused by A. vulgaris and A. rufus, while white sweet clover and red clover sustained more damage from D. reticulatum.

Comparison of damage caused by Arion vulgaris Moquin Tandon and Arion rufus (Linnaeus) (Gastropoda: Arionidae) in pea (Pisum sativum L.)Porównanie uszkodzeń odmian grochu siewnego (Pisum sativum L.) przez Arion vulgaris Moquin Tandon i Arion rufus (Linnaeus) (Gastropoda: Arionidae)

Slugs damage all organs of pea-plants; causing significant damage in cultivations of certain pea (Pisum sativum L.) cultivars. The aim of the study was to identify the degree of susceptibility of different pea cultivars to grazing of two economically important species of slugs Arion vulgaris Moquin Tandon and Arion rufus (Linnaeus) (Gastropoda: Arionidae). The experiments were performed under laboratory conditions. Seeds and seedlings (at the 3–4 leaf stage) of eleven pea cultivars were exposed to feeding of Arion vulgaris and Arion rufus. The rate and extent of plant damages were determined and the susceptibility to injuries was assessed for each cultivar. It was demonstrated that seeds and plants of Muza cultivar were susceptible to feeding of both slug species the most. Additionally, the data revealed that plants of Mentor cultivar were also highly susceptible to A. vulgaris, while plants of Medal cultivar to A. rufus.

Relationships Between Aphids (Insecta: Homoptera: Aphididae) and Slugs (Gastropoda: Stylommatophora: Agriolimacidae) Pests of Legumes (Fabaceae: Lupinus)

Lupin plants are frequently damaged by various herbivorous invertebrates. Significant among these are slugs and aphids, which sometimes attack the same plants. Relationships between aphids, slugs and food plant are very interesting. Grazing by these pests on young plants can lead to significant yield losses. There is evidence that the alkaloids present in some lupin plants may reduce grazing by slugs, aphids and other invertebrates. In laboratory study was analyzed the relationships between aphid Aphis craccivora and slug Deroceras reticulatum pests of legumes Lupinus angustifolius. It was found that the presence of aphids significantly reduced slug grazing on the plants. The lupin cultivars with high alkaloid content were found to be less heavily damaged by D. reticulatum, and the development of A. craccivora was found to be inhibited on such plants.

Effectiveness of Nemaslug in reducing damage plants caused by grey field slug – Deroceras reticulatum (O.F. Müller, 1774)Efektywnośc biopreparatu Nemaslug w ograniczaniu uszkodzeń roślin przez pomrowika plamistego – Deroceras reticulatum (O.F. Müller, 1774)

In 2010–2011 tests were carried out under laboratory conditions on the effectiveness of Nemaslug, applied in three doses, to reduce the damage done to plants of winter rape and Chinese cabbage (at the 4–5 leaf stage) by the slug Deroceras reticulatum. The aim of the research was to evaluate the usefulness of various doses of the nematode Phasmarhabditis hermaphrodita in reducing the number of D. reticulatum in populations in Poland. Observations were done 24 hours after the application of the nematodes, and then consecutively every two days for the period of two-and-a-half weeks. The survival of the slugs were determined, as well as the rate and quantity of plant damage caused by them. The results of the tests showed that the applied doses of the nematode P. hermaphrodita were effective against D. reticulatum. Nine days after the application of the biocontrol agent, there was a significant reduction in damage to the rape and cabbage plants, and after 9–15 days a large proportion of the slugs died. The results suggest that all of the tested doses of the nematode may potentially be useful in controlling D. reticulatum on horticultural and agricultural crops. However, due to particular humidity and temperature requirements of P. hermaphrodita, it is necessary to carry out detailed work to determine the conditions for its application.