Heikki M. T. Hokkanen

Insect biological control and non-target effects: a European perspective.

A 4-year research project on ‘Evaluating Environmental Risks of Biocontrol Introductions in Europe’ (ERBIC) is described, and early results are presented. The project focuses on arthropod biological control (using both microbial and macrobial agents), and uses literature review, case studies with empirical work and various types of modelling to illuminate risk to non-target organisms. These methods will hopefully lead to the development of usable methodologies and guidelines for risk assessment in arthropod biological control, by the project’s completion in 2002. Reviewing existing published and unpublished data on the classical biological control of insects (a first step in this project) has revealed that for only 1.5% of introductions is there some data regarding the realized field

Insect Biocontrol with Non-endemic Entomopathogenic Nematodes (Steinernema and Heterorhabditis spp.): Conclusions and Recommendations of a Combined OECD and COST Workshop on Scientific and Regulatory Policy Issues

Fifteen invited experts from 10 Organisation for Economic Cooperation and Development (OECD) and European countries participating in the European Commissions Cooperation in the Field of Science and Technical Research (COST) Action 819, along with 12 other participants, met to review and debate the potential problems associated with the introduction and commercial use of non-indigenous nematodes for insect biological control. The consensus view of the participants was that entomopathogenic nematodes (EPNs) possess specific biological and ecological features, which make their use in biological control exceptionally safe. All the scientific evidence available supports the conclusion that EPNs are safe to the environment, as well as to production and application personnel, the general public and the consumers of agricultural products treated with them. Only a few potential, but very remote, risks could be identified. Therefore, it was recommended that EPNs should not be subject to any kind of registration. T...

Success in classical biological control

Classical biological control in the past has been characterized by numerous unsuccessful attempts and by relatively few outstanding successes. An analysis of the recent developments in the theoretical and applied aspects of classical biological control reveals, however, that introducing parasites (predators, pathogens, herbivores) against pest organisms apparently has a considerable potential of solving or lessening many important pest problems of the world. In this review, classical biological control was found to be applicable everywhere in the world regardless of temperature or moisture conditions, and native pests were found to be as susceptible to biological control as introduced pests. Biocontrol success was found to be a function of several independent variables (e.g., characteristics of the pest and control organism and the target ecosystem) and many dependent variables (e.g., the methods of selecting, propagating, and introducing the control organism). Knowledge about the interactions between the...

Overwintering survival and spring emergence in Meligethes aeneus: effects of body weight, crowding, and soil treatment with Beauveria bassiana

High overwintering mortality was recorded for Meligethes aeneus in the field in Finland, ranging from 85 to 98% depending on the source of the overwintering population. The main factor explaining variation in survival was the body weight of the beetles in the autumn: only the heaviest beetles survived. Body weight, on the other hand, was influenced by treatment of the rape field soil with Beauveria bassiana, resulting in a 50% decrease in winter survival compared with the reference. The soil treatment did not appear to have direct mortality effects (pathogenesis) on the beetle neither in the summer nor in the winter, and there was no apparent effect on survival of crowding of the insects at the overwintering site. Density dependence in overwintering survival of M. aeneus may function through the availability of pollen food in the autumn, and intraspecific competition for it. Treatment of the rape field soil with B. bassiana may be a feasible way to increase the winter mortality and to lower the pollen beetle populations, but requires further research.

Persistence of augmented Metarhiziumanisopliae and Beauveria bassiana in Finnishagricultural soils

The persistence and penetration into soilof surface-applied unformulated conidia of twoisolates of Metarhizium anisopliae and one of Beauveria bassiana at sites with clay, peat andtwo kinds of sand as their soil types and at depthsof from 0 to 20 cm was studied in 1988–1991 underconditions characterized by permanent snow cover andfrozen soil in the winter time. At 0–5 cm depth, M. anisopliae persisted throughout the experiment atall sites, clay being the most and peat the leastfavourable soil for persistence. Clay and one of thesandy soils were the least and peat the most conducivesoil to penetration of M. anisopliae from thesurface to deeper soil layers and persistence therein.Differences in persistence were evident between thetwo M. anisopliae isolates in the sandy and peatsites, but not in the clay site. Three yearspost‐application there were still enough infectiouspropagules of M. anisopliae in soil of allsites to infect over 80% of the Tenebriomolitor larvae used as baits in samples taken fromthe cylinders of all soils. All the augmentedpropagules of B. bassiana disappeared duringthe first winter after application in clay and one ofthe two sandy sites, but some persistence one yearpost‐inoculation was evident at 0–5 depth in one ofthe sand soils and at 0–5 and 5–10 cm depths in peat.

The making of a pest: recruitment of Meligethes aeneus onto oilseed Brassicas

Populations of the rapeseed pollen beetle Meligethes aeneus F. (Col., Nitidulidae) from areas with 0–16 years of history of intensive rapeseed growing were compared for key ecological characters. During the first 16 years of rapeseed cultivation the reproductive success of M. aeneus increased 200–300% over that of the beetles living on the natural host plants, cruciferous weeds. The increase was linear over time and statistically highly significant, and it did not appear to be related to food quality or to the size of the beetles. During the same period the tolerance to intraspecific competition decreased, possibly due to the relative absence of such competition on the new crop. Furthermore, the optimum population density for M. aeneus to maximize the size of its next generation on summer turnip rape was determined to be 0.5–1.0 beetles/plant, which is slightly below the economic threshold for chemical control (1 beetle/plant). Therefore the practical protection of the rapeseed yield also ensures the highest possible pest population size for the next year. These mechanisms may in part explain the particular noxiousness of the species as a pest all over Europe. In general these data show that after the introduction of a new crop plant into a region, significant changes during the recruitment process in a pestiferous insect may take place, contributing to the future pest status of the insect. It is suggested that such genetic and ecological changes in insects may be a more common mechanism than previously thought in initiating and sustaining pest outbreaks, and that conventional pest management methods may enhance that effect.

Effects of Metarhizium anisopliae on the pollen beetle Meligethes aeneus and its parasitoids Phradis morionellus and Diospilus capito

The efficacy of two Finnish strains of Metarhizium anisopliaeagainst the rape blossom beetle Meligethes aeneus (Coleoptera:Nitidulidae) and the effect on its parasitoids Phradismorionellus (Hymenoptera: Ichneumonidae) and Diospilus capito(Hymenoptera: Braconidae) were studied in laboratory and semi-fieldexperiments. Several bio-assays were performed using either directexposure of the host beetle to the pathogens, or pots containing soilinoculated with M. anisopliae conidia at a rate of 2 ×108 per ml soil. Parasitised and unparasitised M. aeneuslarvae were collected in the field and were placed for pupation in thetest soil. The effect of treatment on M. aeneus andD. capito was estimated after adult emergence, and the effecton P. morionellus was estimated by dissecting hibernating pupae.While both of the M. anisopliae strains were highly pathogenicto M. aeneus adults and larvae upon direct exposure, soiltreatment resulted in no significant difference between the number ofinsects emerging (or found) from the treated and untreatedpots. However, the treated insects appeared to be latently infectedand the actual infection rate had to be estimated after their deathand incubation in a moist chamber. The mortality of the beetles causedby direct exposure to the fungus was 85% (range 70–88%). The rateof latent infection following indirect exposure via treated soil indeep pots in laboratory was 80% (range 49–100%), while that inP. morionellus was only 17% (range 0–85%), and inD. capito significantly higher, 76% (range 72–100%).The results indicate that M. anisopliae is a potentially usefulcandidate to be used as a bio-insecticide to control the pollenbeetle, and that at least the most abundant parasitoid, Phradismorionellus, is less affected than the target pest itself. Thepossible ecological role of latent infections in the host as well asin some of the parasitoids needs to be clarified.

Attempts to control cabbage root flies Delia radicum L. and Delia floralis (Fall.) (Dipt., Anthomyiidae) with entomopathogenic fungi: laboratory and greenhouse tests

One laboratory and three greenhouse experiments were conducted to study the pathogenicity and efficacy of Finnish isolates of entomopathogenic hyphemycetous fungi against cabbage root flies. In Petri dishes, exposure to 1.5 × 1010 spores of Metarhizium anisopliae per dish caused 40–50% mortality of undifferentiated second‐ and third‐stage larvae of Delia floralis, and 1 × 107 spores per dish caused 40–50% mortality of Delia radicum larvae. In one greenhouse test, 1 × 108 and 1 × 109 spores of M. anisopliae and Paecilomyces fumosoroseus reduced the root damage of head cabbage by 20–70% compared with untreated controls, although this was not accompanied by significant reductions in the number of pupae. Only M. anisopliae consistently grew out of larvae and pupae of D. floralis during incubation that followed their recovery from the soil at the end of an experiment testing different formulations of M. anisopliae and Beauveria bassiana, but the frequency of the latent infections of the pest by M. anisopliae was not associated with reduced severity of damage to seedlings of head cabbage.

The safe and rational deployment of Bacillus thuringiensis genes in crop plants: Conclusions and recommendations of OECD workshop on ecological implications of transgenic crops containing Bt toxin Genes

This workshop focused on the ecological implications of transgenic crops containing Bacillus thuringiensis (Bt) genes. An important objective was to derive conclusions and recommendations concerning the safe and rational deployment of Bt genes in crop plants. There were extensive general discussions during the workshop, and a structured round table discussion with all workshop participants on the final day. The topics for the round table were (i) the conditions that make a crop suitable or unsuitable for Bt gene deployment, (ii) the ecological research needed to improve decisions on Bt gene deployment, (iii) the value of promoters and toxin mixtures in resistance management, (iv) the essential components of environmental impact assessments, (v) the need to control imports of crops containing Bt genes and (vi) for New Zealand and Australia, the need for national plans to conserve efficacy of Bt toxins. We have summarized the outcome of these discussions in the following conclusions and recommendations, tak...

Assessing the risk of pest resistance evolution to Bacillus thuringiensis engineered into crop plants: a case study of oilseed rape

Abstract Existing and novel Bacillus thuringiensis toxin-coding genes may be utilised in transgenic oilseed rape to control many of the important insect pest species on the crop, worldwide. Location-specific ecological crop assessment must be used to evaluate the need and possibilities for managing resistance evolution in the target pests, and to ensure sustainability of the control strategy. In some cases, at least, it appears that durable control could be attained in oilseed rape by an integrated control approach, including the use of transgenic crop and among it, about 10% of non-transformed seed to provide refugia for susceptible insect genotypes. Seed mixtures or strip intercropping would be easy to handle also in practice.