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.     

Fossorial Forms of the Water Vole,Arvicola terresths (L.), in Europe1

The species Arvicola terrestris (L.) comprises 2 main life types:an aquatic form which is more common, and a form with fossorial habits which is confined to continental Europe, from the Cantabric Cordilliera to the Carpathian Mountains. However, forms inhabiting a primary wet biotope and a secondary dry one occur in a large border zone in the north of the range of the fossorial form. The fossorial type lives underground in grassland and some types of crops. Very recently, the structure and the occupation of burrows of this subterranean rodent were studied, as well as its digging behaviour and rhythm of activity. The fossorial form of A. terrestris is very easily captured, which makes it possible to estimate its density and to follow population evolution. This microtine shows cyclic population fluctuations and, during outbreaks, causes severe damage to grassland, both by its burrowing activity and by consuming plants. In orchards, it gnaws root systems of fruit trees, mainly of apples. Damage is also serious in gardens and in horticultural crops, especially to plants with fleshy roots. This vole does not eat cereals and does not invade forests. Control methods generally used are surface treatment with organochlorine insecticides (banned in most countries), poisoning (but no efficacious toxic baits are available), fumigation of burrow systems and trapping. Taxonomic research is needed for a better understanding of the status of the different life types of A. terrestris. The biological, ecological and ethological characteristics of these forms must be defined in order to develop and test adequate control methods.     

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.     

Studies of Variations in Weight and Volume of Internal Organs of Microtus agrestis (L.) and their Possible Relation to Fluctuations in Population Density1

This paper discusses the possibility of measuring the cumulative effect upon voles of measurable and immeasurable, endogenous and exogenous stress factors. Variations in certain internal organs (adrenals, thymus, spleen, brown adipose tissue) were studied in 2 populations of Microtus agrestis (L.) in Sweden. Both these populations ended in a crash, but after a different period of time. Variations in the internal organs observed during certain investigation periods up to the crash are discussed. Weight of adrenals appeared to be dependent on population density. Spleen hypertrophy did not seem to appear untU stress reached a certain level and after that was more or less persistent. Thus, the spleen might well be a good indicator of the cumulative effect of exogenous and endogenous stress. The amount of axillary brown adipose tissue could, to a certain extent, be a measure of mean ambient temperature, and, perhaps, could also give information on incipient stress situations. The investigation indicated that there are reasons to assume correlation exists between spleen hypertrophy in voles and their damage to plants.     

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.     

European Field Voles of the Genus Pitymys McMurtrie and their Damage in Agriculture,Horticulture and Forestry1

Research has been carried out to establish the actual incidence in European agriculture and forestry of damage by voles belonging to the genus Pitymys McMurtrie. Unfortunately, the great uncertainty remaining in the taxonomy of these voles and the practical difficulty of recognizing the species responsible for specific damage do not allow us to form, as yet, a complete picture of the situation. Nevertheless, it has been shown that, in Europe, Pitymys voles which are responsible for damage to agricultural crops (irregularly and with varying intensities) can, essentially, be placed in one of the following fundamental species groups:subterruneus (de Sélys Longcharnps), savii (de Séys Longchamps) or duodecimcostutus (de Sélys Longchamps). Without doubt, greatest damage appears to be done by voles of the species group savii which, in a decidedly more southern distribution area, brings about serious damage, particularly to horti-floricultural crops in the Italian peninsula. In Italy, where the Pitymys problem is perhaps more noticeable than anywhere else, the control methods used tend to be inefficacious and do not answer the problem. We hope, therefore, besides conducting a comprehensive biological study of this species group, to carry out adequate experimentation towards developing methods for testing the latest rodenticides as to their efficacy against Pitymys and to develop an adequate application technique.     

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.     

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.     

Damage to Rumex crispus L. and Rumex obtusifolius L. caused by the rust fungus Uromyces rumicis (Schum.) Wint.

Rumex crispus L. and R. obtusifolius L. were infected by the rust fungus Uromyces rumicis (Schum.) Wint. Infections caused severe damage to R. crispus. Rusted plants always had a reduced number of leaves and the significant loss of dry weight of roots and leaves amounted to a minimum of 55% compared with controls. Less damage was caused to R. obtusifolilus, but a significant loss of root and leaf dry weight was also observed. These findings support earlier suggestions in the literature that U. rumicis may be able to play a role in controlling docks, which are common weeds in pastures. Effets pathogènes de la rouille Uromyces rumicis (Schum.) Wint. sur Rumex crispus L. et Rumex obtusifolius L. Des Rumex crispus L. et R. obtusifolius L. ont été infectés par la rouille Uromyces rumicis (Schum) Wint. Les infections ont provoqué des dommages importants chez R. crispus. Les plantes infectées avaient toujours un nombre de feuilles réduit, et subissaient au niveau des racines et des feuilles une perte significative de poids sec d'au moins 55% par rapport aux témoins. Les dommages subis par R. obtusifoliusétaient moins importants, mais une perte significative de poids sec des racines et des feuilles a également été observée. Ces résultats confirment la possibilité déjä suggérée dans la littérature que U. rumicis peut être capable de jouer un rôle dans le contrôle des Rumex, qui sont des mauvaises herbes communes dans les prairies. Ueber Schäden an Rumex crispus L. und R. obtusifolius L., verursacht durch den Rostpilz Uromyces rumicis (Schum.) Wint. Rumex crispus L. und R. obtusifolius L. wurden mit dem Rostpilz Uromyces rumicis (Schum.) Wint. infiziert. Die Infektionen verursachten an R. crispus starke Schädigungen. Befallene Pflanzen wiesen eine reduzierte Anzahl Blätter auf. Die signifikante Verringerung des Trockengewichtes von Wurzeln und Blättern betrug mindestens 55% im Vergleich zu unbefallenen Kontrollen. An R. obtusifolius waren die Schäden geringer; aber auch in diesem Fall wurde eine signifikante Reduktion der Trockengewichte von Wurzeln und Blättern beobachtet. Diese Befunde bestätigen frühere Literaturangaben, wonach U. rumicis bei der Bekämpfung von Rumex-Arten, die verbreitete Unkräuter auf Weiden sind, eine Rolle spielen könnte.     

Azinphos-methyl and carbaryl resistance in adults of the codling moth (Cydia pomonella (L.), Lepidoptera: Tortricidae) from Northeastern Spain

The resistance of Cydia pomonella (L.) to organophosphates is widespread throughout the pome fruit growing areas. The lethal effects of two insecticides inhibitors of the acetylcholine esterase, azinphos-methyl and carbaryl, were evaluated in adults of five and four field populations of the codling moth, respectively. The lethal concentrations (LC₅₀ and LC₉₀) of these insecticides were determined in a susceptible strain from Spain (S_Spain). Topical bioassays using the approximate LC₉₀ values (3000 mg (a.i.)/L of carbaryl and 2000 mg (a.i.)/L of azinphos-methyl) that were obtained in S_Spain were tested as diagnostic concentrations. The enzymatic activities of mixed-function oxidases (MFO), glutathione S-transferases (GST) and esterases (EST) were measured to investigate their potential role in the detoxification of these insecticides.Carbaryl and azinphos-methyl caused ?53% and ?39% corrected mortality, respectively, in field populations, although the diagnostic concentrations applied were twofold and fourfold higher than the maximum concentration registered in Spain, respectively. The activities of MFO and GST were 7.3- to 16.1-fold higher and 2.5- to 3.7-fold higher in all the field populations compared to those in S_Spain, respectively.     

Insect Risks for Introduced and Native Conifers in Northern Europe,especially in the Nordic Countries1

For conifers in the Nordic countries (Denmark, Norway, Sweden, Finland) the geographical origin and ← niche → of conifer insects originating from elsewhere are briefly discussed. Insects associated with seed and small plants have spread best, those associated with bark and timber have followed the trade routes only. Exotic conifers in the region are mainly attacked by indigenous insects.     

Damage Caused by the Rodents Gerbillidae to Agriculture in North Africa and Countries of the Middle East1

The author reviews the problem of damage by Meriones spp. in agriculture in North Africa, especially M. shawi (Duvernoy). This species is subject to outbreaks like those of microtine rodents in Europe. The importance of M. libycus Lichtenstein and M. crassus Sundevall in North Africa and M. persicus (Blanford), M. tristrami Thomas and M. Vinogradovi Heptner in the Middle East is discussed. The 3 latter seem to have become of greater importance in Iran, following changes in agricultural practices.     

Weed control with pre-sowing herbicides in irrigated cotton (Gossypium barbadense L.) and groundnut (Arachis hypogaea L.) in the Sudan. II. Economic, labour requirement, crop safety and operational aspects of trifluralin and benfluralin

Soil incorporated. pre-sowing application of trifiuralin in cotton or of benfluralin in gruundnut, each at 1–68 kg a.i., ha, cut labour requirement for handweeding to levels where the tenant could he largely independent of hired labour, Economic returns from a combination of these herbicides plus supportive hand- weeding for herbicide-resistant species compared favourably with those from hand- weeding only as presently recommended. Application and incorporation of trifluralin and benfluralin fited well into existing practices for seedbed preparation and any likely modifications of these. There was no evidence of crop phytoxicity and crop maturity was not affected. Residue analysis indicated no soil residue problems for crops in rotations and no residues were detected in crop seed. Trifluralin applied many months in advance of cotton planting in the dry season, did not start to disappear until the soils were wetted just before couon planting.     

Occurrence,resistance factors and cross-resistance patterns to herbicides inhibiting acetolactate synthase (ALS) of Echinochloa crus-galli (L.) Pal. Beauv. in Central Europe

Journal of Plant Diseases and Protection - Echinochloa crus-galli (L.) Pal. Beauv. is one of the most noxious weeds in maize cultivation and has evolved target-site resistance to ALS-inhibiting...     

Diflubenzuron and oogenesis in the codling moth,Cydia pomonella (L.)

Diflubenzuron, topically applied (0·5 μg insect^?-1) to Cydia pomonella (L.) at pupal ecdysis disturbed growth and development of oocytes. It delayed the adult ecdysis and caused a decrease in both thickness of the follicular epithelium and the size of the basal oocyte during the pupal development. On the other hand, the size of basal oocytes, the protein content per ovary and the number of oocytes per ovary recorded in newly emerged adults were significantly reduced after diflubenzuron treatment. These results, together with observations in several other species, indicate that the reduction in fecundity and egg viability is probably due to interference of diflubenzuron with the vitellogenesis process.     

Field emergence of Avena fatua L. and A. sterilis ssp. ludoviciana (Dur.) Nym. in Aragón, Spain

Emergence of Avena fatua and A. sterilis ssp. ludoviciana infesting winter cereals during two years and at two sites in Aragon began after sowing in late October and continued for 23 weeks, with 75% of seedlings appearing in the first 9 weeks. The start of emergence was associated with a fall in minimum air temperature to below 9°C and a maximum of less than 20°C. Soil moisture was not limiting, and during winter flushes of seedlings tended to be associated with rises in mean temperature. In contrast with results from other latitudes, A. fatua emerged mainly in autumn at the same time as A. sterilis ssp. ludoviciana.