BioControl

Habitat management to conserve natural enemies has increased biological control of insect pests in various cropping systems [Annu. Rev. Entomol. 45: 175–201, 2000]. We wanted to determine if insect predation in highbush blueberry, Vaccinium corymbosum L. (Ericales: Ericaceae), is influenced by manipulation of edaphic arthropod community and whether management of ground cover in aisles between blueberry rows enhances this community. The first question was studied in blueberry plots bounded by trenches permitting selective movement into plots (ingress) or out of plots (egress), as well as unbounded control plots. We observed a significant effect of boundary type on the arthropod communities’ relative abundance as measured with pitfall traps, with relative abundance highest in ingress plots, intermediate in control plots and lowest in egress plots. Effects of ground arthropod abundance on predation rates were assessed with onion fly, Delia antiqua (Meigen) (Diptera: Anthomyiidae), pupae as sentinel prey. Pupa recovery was greatest in egress boundary plots, intermediate in control plots and lowest in ingress boundary plots. Regression analyses indicate pupal recovery rate decreased as a function of carabid abundance as well as the abundance of non-insect ground predators. To determine if ground cover management influenced natural enemy abundance, aisles were clean cultivated or planted with three ground covers (clover, ryegrass, or buckwheat). Increasing ground cover had a significant effect on the relative abundance of Harpalus pensylvanicus De Geer (Coleoptera: Carabidae). In addition to conserving natural enemies for control of blueberry insect pests, we discuss additional benefits of ground covers that may increase their utility for blueberry production.

La blastogenèse deNomuraea rileyi (Farlow) Samson requiert des besoins très spécifiques. La présence de Tween et une forte concentration en extrait de levure sont indispensables. Contrairement aux conidies, les blastospores obtenues ne sont pas capables de traverser le tégument de l'hôte alors qu'il est démontré que les blastospores de quelques autres espèces sont effectivement entomopathogènes par la voie tégumentaire.

The performance of three species of predatory ladybirds was compared in a flight mill and the effect of diet on their flight parameters was tested. The invasive ladybird Harmonia axyridis Pallas (Coleoptera: Coccinellidae) outperformed Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae) and Adalia bipunctata (L.) (Coleoptera: Coccinellidae) in terms of flight distance, duration and velocity. Harmonia axyridis flew at least two times further, needed three times less breaks and flew two times faster than C. montrouzieri and A. bipunctata fed the same diet. Ladybirds reared on eggs of Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) performed better than their counterparts reared on natural prey (aphids for H. axyridis and A. bipunctata, mealybugs for C. montrouzieri). The findings of this study indicate that comparative flight studies can be useful to identify candidate biocontrol agents with pronounced dispersal abilities and thus can yield significant evidence to be used in an environmental risk assessment. However, it also demonstrates that variability related to mass rearing conditions should not be ignored when standardizing a risk assessment procedure for candidate biocontrol agents.

The prey range of Cryptolaemus montrouzieri was studied in the laboratory to investigate whether the mealybug destroyer can contribute to the suppression of other pest insects besides mealybugs and to assess its potential impact on non-mealybug populations as part of an environmental risk assessment for its use in biological control. Prey tested in these experiments were: tobacco aphid Myzus persicae nicotianae (Sulzer)(Hemiptera: Aphididae), pea aphid Acyrthosiphon pisum (Harris)(Hemiptera: Aphididae), tobacco whitefly Bemisia tabaci (Gennadius)(Hemiptera: Aleyrodidae), southern green stinkbug Nezara viridula (L.)(Hemiptera: Pentatomidae) eggs, western flower thrips Frankliniella occidentalis (Pergande)(Thysanoptera: Thripidae), two-spotted ladybird Adalia bipunctata (L.)(Coleoptera: Coccinellidae) eggs and eggs of the greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae). Larval survival was high to moderate when C. montrouzieri was provided with hemipteran prey and poor to zero when the ladybirds were provided with non-hemipteran prey. Females reared on M. persicae and A. pisum produced similar numbers of eggs as their counterparts fed the citrus mealybug Planococcus citri (Risso)(Hemiptera: Pseudococcidae), but fecundity was significantly lower when the ladybirds were reared on B. tabaci nymphs or on A. bipunctata eggs. Prey species that were found to be less suitable for immature development of C. montrouzieri could still be an adequate food source for reproduction and survival of adult ladybirds. For example, only 8 % of the predator larvae reached the adult stage when provided with A. bipunctata eggs, but females that had developed on eggs of the Mediterranean flour moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) and that were supplied with A. bipunctata eggs from adult emergence on, were only 35 % less fecund than females provided with mealybugs in their adult life. The results are discussed in relation to the development of a suitable methodology for prey/host range testing in the framework of an environmental risk assessment for arthropod natural enemies.

We monitored the activities of the Argentine ant,Iridomyrmex humilis (Mayr), in 3 citrus orchards during 1984 and 1985. We also monitored densities of citrus red mite,Panonychus citri (McGregor), the adult spider mite destroyer,Stethorus picipes Casey [Col.: Coccinellidae], and the predatory mite,Euseius tularensis Congdon [Acarina: Phytoseiidae] during the same period in ant-present and ant-free plots in each orchard. I. humilis was excluded for at least 9 months from trees pruned 60 cm from the ground following a basal application of 1 or 2 % chlorpyrifos 4 EC. Autumn densities ofP. citri in these ant-free plots were significantly lower than those in the plots infested withI. Humilis. S. picipes appeared to be the most important predator, maintaining lowP. citri densities on citrus in southern California in the absence ofI. humilis activity.S. picipes densities increased numerically in response to the early spring and late autumn increases in the density ofP. citri populations. However, in the presence ofI. humilis activity, effective predation was apparently inhibited. Densities ofE. tularensis were unaffected by the presence ofI. humilis, nor didE. tularensis respond to spring or autumn increases in the density ofP. citri populations in any of the orchards.

Survival in the laboratory of Mastrus ridens Horstmann (Hymenoptera: Ichneumonidae) reared on larvae of Cydia pomonella (Linnaeus) (Lepidoptera: Tortricidae) and five species of non-target Tortricidae was compared. Clutch size (numbers of eggs per host larva) and survival were higher on codling moth than on non-target species, and most adults reared from non-target larvae were smaller. F2 generation M. ridens adults reared on Argyroploce chlorosaris Meyrick and Cydia succedana (Denis and Schiffermüller) larvae were also small, with a sex ratio skewed to males. Few parasitoids survived, and they did not appear to have adapted to the non-target species on which their parents were reared. When M. ridens eggs were immediately removed from venom paralysed larvae, no codling moth larvae but most non-target larvae died within a few days. It is suggested that the host-paralysing venom of M. ridens is adapted to ensure the survival of codling moth larvae and is lethally maladapted to non-target species, such that it might be possible to determine ectoparasitoid host range by biochemical or physiological tools that characterise venom or prey response, respectively.

Aphelinus flavus Thompson is a solitary internal parasite. Males and females overwinter as free living adults and appear on sycamore in mid, May. The female consumes aphid body fluids and kills 1 aphid for food for every 1.7 eggs deposited, and parasitises 48 aphids over 27 days. Development from egg to adult requires and parasitises 48 aphids over 27 days. Development from egg to adult requires 57 days. The mortality of parasites while within the nummified host was determined: it was related to hyperparasitism and predation. Mortality due to mummies being brushed off the leaves was also determined.

Studies on the development, fecundity, nutrition and the influence of temperature and humidity onAphytis coheni DeBach, an ectoparasite of the California red scale,Aonidiella aurantii (Maskell) were conducted in an effort to explain the current distribution ofA. coheni in citrus groves in Israel.

The life history ofNephus reunioni, introduced from the Reunioni island has been studied. Optimum temperature for the development of the entomophagous insect is 24–25°C. In this case the population has the highest survival at preimaginal stages, life duration of adults and reproductive capacity. The rate of population growth was calculated by the formula: $$w = exp\frac{{In R_0 }}{T}$$ , were R0-reproduction coefficient, T-generation development time. W shows the daily increase in the predator population and is maximum at 29°C.N. reunioni is capable of successfully developing within the wide range of relative humidity. Relative humidity of 55±5% is optimum for development of the population. Due to its ecological plasticityN. reunioni can be used in biological control of mealybugs on a much greater area than the earlier introducedCryptolaemus montrouzieri (Mulsant).