Laboratory pesticide screening method for the aphid predatory midge Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae)

A laboratory pesticide screening method is described for the aphid predatory midge Aphidoletes aphidimyza. Four acaricides, 10 fungicides, 11 insecticides and one herbicide, all of which are in common usage, were evaluated against both the adult and larval stages of the predator. The acaricide dienochlor, the fungicides benomyl, bupirimate, chlorothalonil, iprodione and hexaconazole, the herbicide tralkoxydim and the insecticides Bacillus thuringiensis and diflubenzuron were all safe to both adult and larval A. aphidimyza. Adults were more susceptible to the pesticides than larvae. Pesticide was exposed to adults as a residue on glass plates and to larvae on a leaf section mounted on agar. The leaf material remained healthy and supported host aphids for several days without deteriorating. The method and apparatus have potential for use with many other pests and beneficial organisms required to be caged for several days on detached leaf material.     

Results of the sixth joint pesticide testing programme of the IOBC/WPRS-working group «pesticides and beneficial organisms»

The side effects of 5 insecticides, 8 fungicides and 6 herbicides on 24 species of beneficial organisms were tested by members of the Working Group «Pesticides and Beneficial Organisms» of the International Organization for Biological Control (IOBC), West Palaearctic Regional Section (WPRS). The tests were conducted by 24 members in 11 countries according to internationally approved guidelines. The insecticide buprofezin (Applaud), the fungicides triforine (Saprol), procymidone (Sumisclex), anilazine (Dyrene), triadimenol (Bayfidan), hexaconazole (Anvil), tridemorph (Calixin) and the herbicides tralkoxydim (Grasp), bentazone (Basagran) were harmless to nearly all the beneficial organisms. Diflubenzuron (Dimilin) affected spiders and the larvae of predatory insects. The remaining 10 preparations were more toxic and should therefore be further tested in semi-field and field experiment on relevant organisms.     

Experimental evidence for density-dependent reproductive output in a coral reef fish

We tested for density-dependent reproduction in a small coral reef fish using field manipulations of density and observational data. Males of the study species, the bridled goby (Coryphopterus glaucofraenum Gill), defend benthic nest sites, within which they spawn with females, and females can spawn repeatedly over an extended breeding season. In small areas, usually only a single male nested at any one time regardless of how many males were present, so the probability of nesting was inversely proportional to density. Nesting males were almost always the largest in the vicinity, suggesting that, for males whose home ranges overlap, social interactions dictate opportunities to nest. Both the per capita rate at which clutches were laid and the number of eggs produced per clutch declined with increasing density, so the per capita rate of egg production was also density dependent. All three measures of fecundity were better predicted by numerical density (numbers per unit area) than biomass (mass of fish per unit area), and were well described as an inverse function of the number of gobies in the vicinity. A simple hypothesis consistent with these results is that a constant number of females spawn, regardless of density. Alternately, the effect of crowding may depend primarily on the number of interacting individuals and affect all females relatively equally. This density dependence could thus contribute to population regulation at the spatial scale over which populations become reproductively closed.     

Effectiveness of Orius laevigatus (Hem.: Anthocoridae) for the control of Frankliniella occidentalis on cucumber and pepper in the UK

Biological control of Western Flower Thrips was sought by the use of Orius laevigatus, an anthocorid bug indigenous to the UK. Rearing methods were successfully devised for this species and glasshouse trials on cucumbers and peppers were conducted. It was not possible to obtain full establishment of O. laevigatus on a cucumber crop, but breeding populations established satisfactorily in the flowers of sweet peppers. On peppers, releases totalling one to two Orius per plant resulted in good thrips control over several months providing that initial thrips numbers were low. Early season supplementary lighting using tungsten bulbs to extend the photoperiod ensured good control of thrips on peppers in February and March by promoting Orius breeding on the crop.     

Control of Western flower thrips (Frankliniella occidentalis Pergande) pupae in compost

Western flower thrips (Frankliniella occidentalis) develops from an active larval stage through to a non-feeding, almost immobile, pre-pupal and pupal stage. This generally occurs in the compost or soil below the plant on which the larvae fed. Control of thrips at this stage in their development offers a chance of utilising pathogens or pesticides not suitable for use in an integrated control programme aimed at adult and larval stages. Trials were done with F. occidentalis pupae and pre-pupae in a soil/peat based compost using 11 pesticides, three fungal pathogens and four species of insect parasitic nematodes. The pesticides malathion and chlorpyrifos-methyl gave the most promising result with 97.5% and 96.5% control, respectively. The fungal pathogen Metarhizium anisopliae proved better when applied as a pre-pupation rather than as a post-pupation treatment (74.5% : 26.6% control). The insect parasitic nematode Steinernema carpocapsae gave 76.6% control when applied at 25 times 10⁴ nematodes litre^-1 of compost. The results are discussed in relation to control of thrips in glasshouses.