Outbreaks and Damage by the Field Vole,Microtus agrestis (L.), since World War II in Europe1

The field vole, Microtus agrestis (L.), is a major pest in horticulture and forestry in all Scandinavian countries, and an important forestry pest in certain regions in central Europe. The most common type of damage is girdling trunks of cultivated trees, usually under the snow cover. In horticulture, the apple tree is the commonest subject of injury, while, in forestry, several deciduous and conifer species are attacked. In Finland and Norway, the garden industry has suffered most, while, in Sweden, the problems are predominantly in forestry. In central Europe, M. agrestis is a forestry pest only. Summation of all losses due to the field vole since World War II amounted to somewhere between 50 and 100 million US Populations of M. agrestis normally undergo cyclic fluctuations. However, comparison of the periodicity of outbreaks in different areas reveals variations, 3 to 4-year intervals dominating in the Scandinavian countries, while the interval in central Europe is generally somewhat shorter. No overall synchrony exists over the geographical range of the species. Present knowledge concerning the demography and habitat dynamics of M. agrestis is briefly reviewed. Current possibilities for preventing damage by M. agrestis are much dependent on the individual value of the potential subjects of injury. High value stands, like apple gardens or seed orchards of forest trees, can be protected by means of mechanical guards. However, current means of combating damage in forest plantations are badly limited. Surface spraying with toxaphene and poison baits is practised in central Europe, while, in the Scandinavian countries (except Denmark), no chemical means are used today. Development of new compounds to be used as surface sprays, or specific baits for M. agrestis, is urgently needed. Research on bio-control methods should also be intensified.     

A Program for Control of Damage by the Field Vole,Microtus agrestis (L.), in Seed Orchards of Forest Trees1

For providing high-quality seed for forest nurseries, a large-scale seed cultivation program, including laying down 3,790 ha of seed orchards of pine, spruce and other forest trees, was established in Finland in the early 1960's. In particular, pine grafts are extremely vulnerable to damage by rodents, especially the field vole, Microtus agrestis (L.). An integrated rodent control program for all the existing seed orchards was established in 1969. From that time, rodent populations were surveyed every year according to a common scheme based on the Small Quadrat Method (SQM). Short-term forecasts and specific control instructions were issued shortly after the survey. Earlier, the principal method of controlling voles was surface treatment with endrin. At present, the bulk of grafts is protected by mechanical guards round the stems. Investments in guard materials, as well as labour costs of preparing and installing the guards, constituted more than 90% of all control costs from 1969 to 1976, and amounted to about 5 million Fmk. Total costs of rodent surveillance and supervision of the program were about 6% of control costs. Since the establishment of this integrated control program, the absolute numbers of grafts destroyed has considerably decreased, even though the area of seed orchards had more than doubled; thus the large investments in vole control have already been recovered.     

Population Dynamics of the Field Vole (Microtus agrestis [L]): a Model1

The basic hypothesis underlying a population dynamics model for the field vole (Microtus agrestis [L.]) in central Scandinavia is described and discussed. The hypothesis is that most aspects of population dynamics of the field vole may be understood by analyzing the nutritional (energy and matter) balance of individual animals and their differential allocation of available nutrients. Digested nutrients are assumed to be utilized for maintenance cost, M; growth, A S; reproduction, R; and dispersion behaviour (including dispersal), D. The simulation model whose main ideas are described verbally is being developed at present. The model is intended to simulate density, age structure, reproductive activity of different categories of the population and spatial distribution; grazing impact apportioned among the most important potential food species (or group); interaction with sympatric rodents, their predators and parasites. Special emphasis is placed on the spatial heterogeneity of the landscape. The population dynamics model is of the Monte Carlo type and considers the realization of a series of events by calculating average probabilities and “drawing” random numbers. The model simulates individual animals in a large heterogeneous area. Qualitative predictions based on our basic hypothesis are discussed and compared with available field information.     

Ecological and Toxicological Bases of Directed Control of Arvicola terrestris (L.) and Microtus arvalis (Pallas) in Agricultural Crops 1

In order to protect crops during outbreaks of Arvicola terrestris (L.) or Microtus arvalis (Pallas), it is necessary to have formulations with acute action and high rodenticidal potential; rodenticides should be applied as baits corresponding to the hygrotrophic specialization of the species. When compared with zinc phosphide, Gliftor provides reliable control of voles in any season. The outlook of bactorodencide (bacterial preparation) applications is being determined with particular reference to their ecological effects.     

Consumption by and Agricultural Impact of the Common Hamster,Cricetus chcetus (L.), on Cultivated Fields1

Energy flow through a hamster population and the impact of this population on field crops were estimated on the basis of population dynamics, rhythm of activity, metabolic rate, and consumption and utilization of natural diets.     

Outbreak of Arvicola terrestris in rice fields in Yugoslavia1

Macedonia is the southern boundary for the distribution of Arvicola terrestris (water vole) in the Balkan peninsula. Until recently, these voles were found in the region only sporadically, showing none of the cyclic population fluctuations characteristic of microtines in the continental part of Europe. An investigation was started in 1984 when the first visible signs of damage to rice in Ko?ansko Valley, caused by numbers of voles, were noted. Since then, population numbers have increased, reaching a density of 1000 individuals per ha on one locality. The causes of such an unexpected outbreak and the methods for determining role abundance are discussed. The construction of a dam and the extension of rice cultivation have reduced the natural habitats of both vole predators and their competitors. Increased pesticide and fertilizer usage have also affected the fauna unfavourably. Efficient control was attained by means of zinc phosphide baits, specially before the rice growing season (i. e. in winter and early spring).     

Integrated control of the fossorial form of Arvicola terrestris in orchards1

For the replacement of endrin for Arvicola terrestris control in The Netcerlands, an integrated control scheme has been developed. The scheme includes: cultivating arable crops during at least one year before planting of the trees; mole control to prevent easy access of A. terrestris; planting trees in wire netting at the edges of the orchard; early detection of damage, so that spot treatments are still feasible; only when damage is widespread, overall treatment with bromadiolone.     

Impact of the Common Vole,Microtus arvalis (Pallas) on Winter Wheat and Alfalfa Crops1)

Impact of the common vole, Microtus arvalis (Pallas), upon the winter wheat and alfalfa crops was determined. Net-bottomed coops were used for estimating the effect of vole grazing. Exposure of winter wheat to vole grazing at the stages of earing and flowering was the most harmful. Losses were up to 91% of the potential crop yield, while the proportion of the best grain size fraction (2.8 mm) dropped to a minimum level. Coefficients reflecting the influence of vole grazing on the crop were determined. The coefficient TOTAL is an index of the total impact of consumption. The impact, I_t, at time t equals the consumption, Ct, at this time multiplied by the value of TOTAL. For alfalfa, these coefficients range from 1.28 to 11.73. The results obtained in this study have made it possible to determine the effective rodent pressure on crop yield.     

The Levant Vole,Microtus guentheri (Danford et Alston, 1882). Economic Importance and Control1

The levant vole, Microtus guentheri (Danford et Alston), the only vole of major economic importance in the Middle East, is the species responsible for the often disastrous mice outbreaks known in this region since antiquity. Population cycles of vole populations and especially the impact of mass outbreaks have been less marked in recent times as a result of changes in cultivation methods, the introduction of new, less vulnerable crops (e.g. cotton) and the elimination of various former sources of infestation and spread of voles (drainage of swamps, regulation of rivers, etc.). On the other hand, new, permanent reservoirs of voles have been created; as, for instance, in alfalfa fields and orchards with permanent vegetation cover. Loss of crops in relation to expenditure of control in Israel is discussed. Various methods of control and rodenticides are reviewed. Organization of control operations, timing of control treatments as well as the need for forecasting impending vole outbreaks are emphasized.     

Methods of Laboratory Toxicological Investigations on the Common Vole (Microtus arvalis [Pallas])1

This paper reports on some laboratory methods for evaluating the toxicity of rodenticides to the common vole. Test conditions including the experimental animals used, their housing, feeding and handling (measuring body weight, marking of the individuals, route of administering the toxicant), test materials and observations are presented. New toxicants were screened simultaneously on white rats and on voles. For each compound, the following data were determined: a) the acute (single dose) approximate LD₅₀ (= ALD₅₀), b) the acute (single dose) LD₅₀, as well as the multiple dose toxicity for anticoagulants, c) the approximate 5-day LD₅₀ and d) the 5-day LD₅₀. For the determination of a) and c), about 6 animals were used. The LD₅₀ values were determined by giving 6–8 doses to each of 10 rats and 4 doses to each of 4–6 voles. A brief report is given on the determination of the joint toxic action of the 2 chemicals. Rodenticidal formulations were tested on voles in various no-choice and choice feeding tests. No-choice tests with compounds having an acute toxicity were carried out for 24 h, those with anticoagulants for 5 × 24 h and those with narcotics for 2 × 24 h. The corresponding periods for choice tests were 2 × 24 h, 5 × 24 h and 4 × 24 h, respectively. Preference and repellency tests were also carried out. The stability of a rodenticide in baits exposed to weather, as well as the effectiveness of fumigants on solid carriers were investigated under simulated environmental conditions.     

Evaluation of insecticides for the control of the green vegetable bug,Nezara viridula (L.) (Hemiptera: Pentatomidae), on sweet corn,Zea mays (L.), in New Zealand

The efficacy of insecticides for the control of Nezara viridula (L.) (Hemiptera: Pentatomidae), the green vegetable bug, was tested in laboratory and field trials. Bioassays of 11 insecticides against field-collected adults were used to select two insecticides for a field experiment conducted in a process sweet corn crop, Zea mays (L.) (cv. Punch), near Tolaga Bay on the east coast of the North Island, New Zealand. Lambda-cyhalothrin (as 200 ml Karate®/100 litres water ha m 1 ) and methamidophos (as 1 litre Tamaron TM /100 litres water ha m 1 ) were tested against a water control. Both insecticides demonstrated efficacy, with respective mortality rates of 87 and 83% compared with 2% in the control. Green vegetable bug flew into the experimental crop in large numbers over 48 h before the start of the trial. Damage thresholds were exceeded in two of the three control plots within 7 days of the green vegetable bug first invading the crop, leaving only a very small 'window' for insecticide application. Success or otherwise of these insecticides is therefore likely to be dependent on the timing of application as well as on the efficacy of the products themselves.     

Methods to control the two forms of Arvicola terrestris in orchards in the Federal Republic of Germany1

Different methods had to be developed in the Federal Republic of Germany (FRG) for the control of the fossorial and the aquatic form of Arvicola terrestris. The fossorial form could be controlled on small areas by trapping but, on large areas where this is not feasible, satisfactory results were obtained by fumigation with carbon monoxide or carbon dioxide. The latter was judged superior as it does not endanger man and proved relatively humane. Sound-emitting devices that were tested against fossorial A. terrestris showed no effect at all. To control the aquatic form, a floating poison-bait station was developed. It was tested with baits containing bromadiolone, chlorophacinone or calciferol during 2 years on an area of 300 ha. Best results were achieved with fresh carrots soaked with chlorophacinone. Careful checks of the area under investigation did not reveal any evidence of secondary poisoning of non-target species.     

Distribution and Ecology of the Russian Wheat Aphid,Diuraphis noxia (Kurdj.), expanded to Central Europe (Hom.: Aphididae)

A part of the territory of the Czech Republic represents the up-dated northern limit of distribution (status 1997) which the Russian wheat aphid (=RWA),Diuraphis noxia (Kurdj.) has reached during its expansion from the southeast to central Europe. The newly defined area is classified as one of the adventive routes which may be derived from the main expansion of RWA from its native home (central-western Asia) into the broader Mediterranean area. Distribution and its history, and ecology (life-cycle, host plants, seasonal history, both native and introduced natural enemies) of RWA are presented on ground of field evidence and trials obtained in 1995–1997 in the Czech Republic. The origin of RWA, its distribution and establishment in the target area, as well as prognosis of its further expansion, are reviewed and discussed. Steps and approaches to RWA detection in the crop, as well as some notes on its management, are added.     

Attraction and antennal response of the common wasp,Vespula vulgaris (L.), to selected synthetic chemicals in New Zealand beech forests

BACKGROUND: The common wasp, Vespula vulgaris (L.), and the German wasp, Vespula germanica (F.), are significant problems in New Zealand beech forests (Nothofagus spp.), adversely affecting native birds and invertebrate biodiversity. This work was undertaken to develop synthetic attractants for these species to enable more efficient monitoring and management. RESULTS: Seven known wasp attractants (acetic acid, butyl butyrate, isobutanol, heptyl butyrate, octyl butyrate and 2,4‐hexadienyl butyrate) were field tested, and only heptyl butyrate and octyl butyrate attracted significantly higher numbers of wasps than a non‐baited trap. Accordingly, a series of straight‐chain esters from methyl to decyl butyrate were prepared and field tested for attraction of social wasps. Peak biological activity occurred with hexyl butyrate, heptyl butyrate, octyl butyrate and nonyl butyrate. Polyethylene bags emitting approximately 18.4–22.6 mg day^?1 of heptyl butyrate were more attractive than polyethylene bags emitting approximately 14.7–16.8 mg day^?1 of heptyl butyrate in the field. Electroantennogram (EAG) studies indicated that queens and workers of V. vulgaris had olfactory receptor neurons responding to various aliphatic butyrates. CONCLUSION: These results are the first to be reported on the EAG response and the attraction of social wasps to synthetic chemicals in New Zealand beech forests and will enable monitoring of social wasp activity in beech forests. Copyright © 2009 Society of Chemical Industry