In laboratory feeding experiments, larvae of Chrysoperla carnea consumed up to 790 Chaetosiphon fragaefolii during their development. In gauzehouse experiments, releases of C. carnea larvae significantly reduced numbers of C. fragaefolii on potted strawberry plants. In open field experiments numbers of C. fragaefolii were significantly reduced at release rates of eight chrysopid larvae per plant, but a release experiment on larger strawberry plants grown under protection did not give a significant reduction in aphid numbers, even at a release rate of 25 larvae per plant.

SummaryThe development rates and fecundity of three important pests of strawberry in the UK were determined over a range of temperatures. Development time of the strawberry tarsonemid mite, Phytonemus pallidus, from egg lay to adult, ranged from a mean of 28.4 days at 12.5°C to 8.8 days at 25°C. No nymphs developed to adult at 10°C. Females lived for up to 45 days and laid a mean of 24.3 and 28.5 eggs at 20°C and 25°C respectively. Total development time from egg lay to adult for the strawberry blossom weevil, Anthonomus rubi, ranged from a mean of 95.7 days at 10°C to 18.2 days at 25°C. Mean fecundity at 20°C was 157.6 eggs, and the oviposition period averaged 71.6 days. When nymphs were reared on strawberry, development of the European tarnished plant bug, Lygus rugulipennis, from egg lay to adult, ranged from 83.8 days at 15°C to 28.8 days at 25°C. Development times on groundsel were shorter and ranged from 65.6 to 22.2 days at 15°C and 25°C. Only two nymphs developed to adults at 10°C; no eggs hatched at that temperature. Mean fecundity at 20°C was 75.4 eggs, but ranged from 23 to 179. Under a fluctuating temperature regime of 10°C for 12 h:20°C for 12 h, nymphs of L. rugulipennis took 40.3 days to become adult on strawberry, and 33.4 days on groundsel. Simple linear models fitted the developmental rate ‐ constant temperature relationship well for all species, accounting for 95–98% of the total variation in observed developmental rates. Development under fluctuating temperatures illustrated the potential problem of extrapolating linear models beyond the conditions of the experiment.

Two species of Neoseiulus, N. californicus and N. cucumeris, showed potential for biocontrol of phytophagous mites on strawberry. N. californicus controlled Tetranychus urticae on potted strawberry plants in a gauze-sided glasshouse at temperatures comparableto early summer in the UK (8–20°C). Both species of phytoseiid reducednumbers of the tarsonemid Phytonemus pallidus on potted strawberry plants under glasshouse conditions (15–23°C). In several experiments reductions in the range of 71–81% in numbers of tarsonemid active stages and eggs, compared to non-release plants, were obtained. The importance of establishing a suitable predator: prey ratio at an earlystage was demonstrated in an experiment where an initial ratio of 1 N. cucumeris: 10 P. pallidus gave a greater degree of controlthan 1:20 or 1:40.

The natural enemies of the more important arthropod, nematode and mollusc pests of strawberry in northern and central Europe and their use as biocontrol agents are reviewed. Most pests of strawberry are polyphagous and they and their natural enemies occur on other host plants (especially Rosaceae) as well as on other crops. Strawberry cultivation methods, including protected cultivation and other methods of extending the fruiting season, soil sterilization, polythene mulching and pesticide spray programmes have profound influences on the pest and natural enemy complex, though such effects have not been quantified adequately. All the pests of strawberry reviewed have natural enemies, though some pests (e.g. capsid bugs) have few. A few natural enemy groups are known to act as important natural limiting factors in pest population development in commercial strawberry crops. Two examples are naturally-occurring phytoseiid predatory mites which regulate pest mite populations, and predatory carabid beetles which regulate root weevil populations. Apart from the introduction of predatory phytoseiid mites to control two-spotted spider mite, biocontrol is not widely used in commercial practice. Other biocontrol approaches are known to be efficacious, but are too costly in comparison with conventional insecticides for commercial adoption (e.g. nematodes for slug control). Several biocontrol approaches have been researched and have potential for further development and exploitation and there is considerable opportunity to develop new approaches. Research effort should concentrate on those for common pests, which are controlled currently by frequent sprays of broad-spectrum insecticides, e.g. aphids, blossom weevil, capsids and vine weevil. As strawberry is often grown as an annual or short-term perennial crop, exploiting natural populations of natural enemies is difficult. More effort needs to be devoted to the development of microbial and nematode biocontrol agents, which can be used as biopesticides. Protected cultivation of strawberry provides more favourable conditions for exploitation of biocontrol including introduction of insect predators and parasites.

Summary Cultivars and advanced selections of everbearing strawberries were tested for their resistance to the European tarnished plant bug, Lygus rugulipennis. No consistent differences in oviposition preferences were found in choice tests, and no differences were found in the proportions of eggs that hatched successfully. However, significant differences were found between the weights of nymphs reared on three cultivars. In a field experiment, amounts of fruit damage caused by L. rugulipennis were lower on cv. Bolero than on three other cultivars despite no significant differences being found between the numbers of L. rugulipennis nymphs on the different cultivars when the fruits were in the susceptible early development stage. Counts of nymphs on seedling progeny where cv. Bolero had been used as a parent were not lower than on those from other crosses. It seems likely that cv. Bolero has no resistance to L. rugulipennis, but rather a greater tolerance to feeding by this insect.

In experiments in which the European tarnished plant bug, Lygus rugulipennis, was caged on the developing flowers or young fruits of strawberry, the insects caused malformation of the fruits. Another species of capsid, Plagiognathus chrysanthemi, caused similar damage; this species is less numerous than L. rugulipennis on late-season crops of strawberry in UK. Other insects which sometimes occur in large numbers in the flowers of late-season strawberry, i.e. various species of thrips and pollen beetles, did not cause fruit malformation in caging experiments, though thrips sometimes caused discoloration of the fruit. In field experiments where numbers of L. rugulipennis were reduced by the use of insecticides, the amount of misshapen fruit was reduced greatly compared to untreated plots. Correlations between the numbers of L. rugulipennis present at the early stages of fruit development and damage scores for fruit deformity were highly significant. This capsid is likely to be the major cause of fruit malformation in late-season crops of strawberry in the UK.

Various species of plants in the family Asteraceae were shown to be hosts for the European tarnished plant bug Lygus rugulipennis and one, Matricaria recutita, was chosen as a potential trap plant for adults of this capsid species on their migration into fields of late-season strawberries from other host plants in July. There was a delay in the build-up of populations of nymphs of L. rugulipennis on strawberries surrounded by a barrier strip of M. recutita compared to those without a barrier, but overall there were no consistent reductions in populations of the pest. Numbers of L. rugulipennis on the trap plant were small until late August. In a similar experiment using an alternative trap plant, Medicago sativa, no significant reductions in the numbers of L. rugulipennis were found on strawberries with the trap barrier, despite large numbers of the pest insect being found on this trap plant.Although predatory arthropods such as spiders, Orius spp., and nabids, and hymenopterous parasitoids were found on the trap plants, there was no indication that they became more numerous on the strawberry plots inside these barriers than on those without surrounding trap plants.

The parasitoids of arthropod pests of apple and pear in northern and central Europe and their use as biological control agents are reviewed. The review demonstrates that apple and pear pests are host to a lar ge and varied parasitoid fauna. All important pests are known to be host of parasitoids, but many parasitoids play only a minor part in regulating populations of their host. However, many parasitoid species are important natural enemies and some effectively regulate pest populations in unsprayed and/or commercial (insecticide sprayed) apple or pear orchards either individually or as part of parasitoid guilds. Exploitation/fostering of existing populations of parasitoids has been demonstrated to be art effective or partially effective approach for natural control of several important pest species. Important examples include natural regulation of the apple sawfly by Lathrolestes ensator and Aptesis nigrocincta, of the summer fruit tortrix moth by Colpoclypeus florus and Teleutaea striata, of leaf midges by Platygaster demades, of woolly aphid by Aphelinus mall and of leaf mining moths by guilds of parasitoid species. Introduction of parasitoids is an alternative approach to the exploitation of parasitoids already present in the orchard. This approach has been little explored and its success rate has been low: mainly confined to the control of non-indigenous pests by introducing parasitoids from their native region. Mass production methods for parasitoids are difficult and costly and are likely to be economic only where long-term populations can be established. Even where lore cost mass culture techniques are developed, the degree of control may not be high enough to prevent economic pest damage ns demonstrated by negative results with mass release of Trichogramma Egg parasites for control of tortricids in orchards. Suitability of the orchards habitat is recognized as crucial to the success of individual parasitoids. Key requirements ore adequate populations of the pest(s) and/or alternative hosts, suitable shelter, overwintering sites or food sources and avoidance of harmful effects of pesticides. Many species ore highly sensitive to broad-spectrum insecticides, especially, in the adult life-stage. Avoiding the harmful affects of insecticides is crucial to successful exploitation. The use of insecticides needs to be avoided either altogether or at crucial times in the parasitoids' life cycle: or less harmful alternatives need to be used Numerous parasitoids could potentially be exploited ns biological control agents but hitherto have received little attention because little is known about them and/or because they are sensitive to broad-spectrum pesticides and are thus virtually absent from commercial orchards. The aim of future studies should be to develop effective strategies for establishing equilibria between important pests and their parastitoids, with pest damage rarely exceeding the economic threshold.

SummarySurveys were made of fields of strawberries of various cultivars and flowering/fruiting seasons in south-east England to determine the composition and relative abundance of the beneficial arthropod fauna. Most fields had a minimal spray programme, with nil or one insecticide treatment per season. Spiders were consistently the most abundant group of polyphagous predators in suction or tap samples. Anthocorids, mainly Orius spp., sometimes became numerous, particularly on everbearer cultivars. Numbers of coccinellids, chrysopids and predatory mirids were usually very small. Hymenopteran parasitoids were often numerous in fields with large aphid populations. Two species of phytoseiid mites and the larvae of a cecidomyiid midge were found in leaf samples, in association with colonies of two-spotted spider mite. Aphid numbers reached damaging levels in some fields, despite the presence of large numbers of predators. Spider mites also reached high numbers in some fields, but populations declined where predatory phytoseiids colonized the plants. Large variability in numbers of beneficial arthropods occurred between fields over short distances.

In field experiments, insecticides used against pests on strawberry showed differential toxicity to the major groups of beneficial arthropods. Pirimicarb and heptenophos had no significant effect on spiders, staphylinids and anthocorids, or on hymenopteran parasitoids. Chlorpyrifos, demeton-S-methyl and the pyrethroids cypermethrin and bifenthrin reduced populations of beneficial arthropods in some experiments. Some of the variation in toxicity between experiments may have been due to differences in the availability to predators of refugia, where predators could escape contact with spray or residues.

Publisher Summary The development of effective pesticides appears to offer an efficient and cost effective solution to the problems of eriophyoid mite control. However, not all eriophyoid mites are easily controlled by the use of pesticides. Leaf or fruit vagrant species are usually exposed throughout their life cycles and are, thus, subject to suppression with various pesticides. Other species, including the gall, blister, and bud mites, spend part of their life cycle within shelters among plant tissues and so are protected from a direct contact with potentially effective pesticides. The effective spraying period is often restricted to the time when the mites are migrating from these shelters to invade newly developing plant tissue. Effective treatments require an acaricide with extended residual activity on the plant surface during the migration period. It is vital to be aware of the effects of many pesticides against different families of mite. This chapter illustrates the differential activity against eriophyoid and tetranychid pests of citrus and apple.

Comparisons were made of numbers of fruit set on individual blossom clusters or whole trees of apple cvs Bramley's Seedling and Cox's Orange Pippin infested with large numbers of apple rust mite, Aculus schlechtendali, and on those infested with small numbers of mites following the use of a pre-blossom acaricide or glue barrier. There was no clear evidence that mite feeding on the leaves of the blossom clusters reduced the initial fruit set, even when numbers of rust mites reached several hundred per primary spur leaf. Photosynthetic rate was not reduced on primary spur leaves over a range of 3-160 rust mites per leaf in May.

There are two types of eriophyoid mites on apple and pear: (1) the free-living eriophyoids or rust mites and (2) those that live much of their lives within a shelter, the gall or bud mites. Damage caused by rust mites on apple and pear has been recognized for some time, but in many countries their pest status seems to have increased since the late 1960s. This is probably because of the combination of factors, including a change from fungicides, such as sulfur and binapacryl that had a suppressive effect on mite populations, to non-acaricidal compounds. The increasing use of insecticides, such as synthetic pyrethroids, also favored rust mites and they also probably developed resistance to some pesticides. Improvements in orchard management, such as more frequent replanting and better nutrition, have led to more luxuriant tree growth and better leaf quality, thus, stimulating mite development. Much of the damage caused by eriophyoids on apple and pear is to the leaves. However, at times, fruit is also affected and given severe quality standards for fruit marketing.

The potential of the entomogenous fungus Metarhizium anisopliae as a microbial control agent for vine weevil (Otiorhynchus sulcatus) larvae was examined on a range of outdoor hardy nursery stock species. A curative application of M. anisopliae conidia (5 x 10(8) conidia l-1 compost) reduced larval numbers by 62% on Skimmia japonica 'Rubella' and by up to 43% on Viburnum plicatum 'Mariesii'. Four M. anisopliae isolates were examined and all reduced the larval populations on both species. However, the reductions were only significant with strains 159-83 and 100-82 on S. japonica 'Rubella' and 100-82 on V. plicatum 'Mariesii'. Larval development on two other species (Hydrangea macrophylla 'Blue Wave' and Thuja plicata 'Zebrina') which had been treated with 0.05% Triton X-100 (the control treatment) was very poor and therefore it was not possible to determine whether or not the fungal drench had any effect. The experiment was repeated in the following year at two different sites, East Malling and Littlehampton, using a prophylactic drench of two M. anisopliae isolates on a greater number of plant species. Strain 275-86 was more effective than 159-83 on all species at East Malling, with the exception of V. davidii. The difference was less pronounced at Littlehampton and the results from the two isolates were similar. Larval control was highly variable and species dependent with a reduction in larval numbers ranging from zero to 96% and zero to 90% at East Malling and Littlehampton respectively. The larval populations in pots treated with Triton X-100 were also highly variable, ranging from zero (Chaemaecyparis lawsoniana 'Stardust', Dianthus 'Maria', Escallonia 'Crimson Spire' and Pittosporum tenuifolium 'Garnettii') to 17.8 larvae per pot (Ribes nigrum 'Baldwin'). The results indicate the potential of M. anisopliae and demonstrate the complexity of plant-weevil-fungus interactions.

In a 4-year trial in apple orchards, the effectiveness of the predatory mite Typhlodromus pyri as a biological control agent against the fruit tree red spider mite, Panonychus ulmi, and the apple rust mite, Aculus schlechtendali, was examined under different pesticide regimes. T. pyri survived insecticide programmes based on organophosphates or carbaryl and, in the third and fourth year of the OP programme and the fourth year of the carbaryl programme, regulated phytophagous mite populations to such an extent that no acaricides were necessary. In plots treated with a synthetic pyrethroid insecticide programme, few T. pyri were found and acaricide treatments were required in each year. A pest-management system that integrates this biological control of phytophagous mites with chemical treatment for other pests is described.

The potential of two species of predatory phytoseiid mites to control the two-spotted spider mite, Tetranychus urticae, on unprotected field-grown strawberries in the UK was investigated. Typhlodromus pyri, a native species, was able to control T. urticae in some circumstances, but was less effective under hot, dry conditions. Natural colonization by this species is likely to be too slow in plantations of 1 - 2 years life. Attempts to introduce this predator to strawberry fields on cut apple shoots were unsuccessful. The exotic predator Phytoseiulus persimilis, which is available from commercial sources, gave very good control of T. urticae when released onto strawberry plants in June. A release earlier in the year was less successful, so to prevent early build-up of mites and possible plant damage it may sometimes be necessary to reduce spider mite numbers early in the year with an acaricide, before a later release of P. persimilis. The success of this integrated control strategy was demonstrated.

The insect-pathogenic fungusMetarhizium anisopliae attacks larvae of the black vine weevil,Otiorhynchus sulcatus, an important pest of soft fruit and ornamental plants. In trials on strawberries and potted ornamental plants growing outdoors, a strain of this fungus has given promising results for control of the pest. Further work is required to determine the most effective dose rates, methods and timing of application.

Using a leaf disc transformation procedure andAgrobacterium- mediated gene transfer, transgenic apple and strawberry plants have been produced that carry a gene encoding a cowpea trypsin inhibitor (CpTl). This gene is known to confer resistance to several lepidopteran and coleopteran insect pests. Scientific and regulatory aspects of this type of work are discussed.