Ferenc Szentkirályi

Optimization of a Phenylacetaldehyde-Based Attractant for Common Green Lacewings (Chrysoperla carnea s.l.)

In field trapping tests, the catch of Chrysoperla carnea sensu lato (Neuroptera: Chrysopidae) increased when acetic acid was added to lures with phenylacetaldehyde. The addition of methyl salicylate to the binary mixture of phenylacetaldehyde plus acetic acid increased catches even further. The ternary blend proved to be more attractive than β-caryophyllene, 2-phenylethanol, or 3-methyl eugenol (compounds previously described as attractants for chrysopids) on their own, and no influence on catches was recorded when these compounds were added as fourth components to the ternary blend. There were minimal changes in activity when (E)-cinnamaldehyde or methyl anthranylate (both evoking large responses from female or male antennae of C. carnea in this study) were added, although both compounds showed significant attraction on their own when compared to unbaited traps. In subtractive field bioassays with the ternary mixture, it appeared that the presence of either phenylacetaldehyde or methyl salicylate was important, whereas acetic acid was less so in the ternary mixture. The ternary blend attracted both female and male lacewings at sites in southern, central, and northern Europe. Possible applications of a synthetic attractant for lacewings are discussed.

Attraction of Chrysoperla carnea complex and Chrysopa spp. lacewings (Neuroptera: Chrysopidae) to aphid sex pheromone components and a synthetic blend of floral compounds in Hungary.

BACKGROUND The deployment of synthetic attractants for the manipulation of lacewing populations as aphid predators is currently used in integrated pest management. This study investigates a synthetic bait comprising floral compounds previously found to attract the Chrysoperla carnea complex, and, for the first time, the aphid sex pheromone components (1R,4aS,7S,7aR)-nepetalactol and (4aS,7S,7aR)-nepetalactone, in field experiments in Hungary, for their ability to manipulate lacewing populations. RESULTS The synthetic floral bait attracted both sexes of the Chrysoperla carnea complex, and Chrysopa formosa Brauer showed minimal attraction. The aphid sex pheromone compounds alone attracted males of C. formosa and C. pallens (Rambur). When the two baits were combined, Chrysopa catches were similar to those with aphid sex pheromone baits alone, but carnea complex catches decreased significantly (by 85-88%). CONCLUSION As the floral bait alone attracted both sexes of the carnea complex, it showed potential to manipulate the location of larval density via altering the site of oviposition. Aphid sex pheromone compounds alone attracted predatory males of Chrysopa spp. and can potentially be used to enhance biological control of aphids. For the carnea complex, however, a combination of both baits is not advantageous because of the decrease in adults attracted. Assumptions of intraguild avoidance underlying this phenomenon are discussed.

Spatial and temporal variation of apple blossom weevil populations (Col., Curculionidae) with recommendations for sampling.

The variance in apple blossom weevil, Anthonomus pomorum L., populations was studied in two experimental orchards in Hungary. Over a 15 year period there were four peaks in abundance, at three to six year intervals. Blossom infestation was greatest in the six orchard rows closest to a mixed oak forest. Variance in percent blossoms infested was as great between adjacent branches as between branches on opposite sides of the tree. There was greater variance in infestation percent between adjacent trees than between clusters of trees in different parts of the orchard. There was a slight positive correlation (r = 0.18) between blossom density and the percent infested blossoms. A recommended sampling plan of three branches from ten trees would give a precision of ± 3 % infested blossoms with an error of 0.05. Sampling should be in a stratified random pattern with concentration of samples near the orchard edge, especially edges adjacent to forests.

Manipulation of oviposition and overwintering site choice of common green lacewings with synthetic lure (Neuroptera: Chrysopidae)

Common green lacewings (Chrysoperla carnea species complex) are important predators of several insect pests, particularly aphids. Due to their potential in biological control, several efforts have been made to find means to retain common green lacewing adults or even to increase their numbers at a given site. In the course of field experiments conducted in Hungary and Norway, we tested the effect of a known ternary bait (phenylacetaldehyde, methyl salicylate, acetic acid) on oviposition and overwintering site choice of common green lacewings. In an orchard in Hungary, overwintering chambers were set up with and without baits. For the experiment on oviposition in Norway, a number of lacewing eggs were compared on trees with and without baits in selected sectors of the canopy. With the ternary bait, more common green lacewings could be attracted to overwintering chambers, and also significantly more eggs were found in the vicinity of baits than in other selected parts of the canopy, suggesting that this bait has the potential to manipulate both overwintering site choice and oviposition site choice of these important beneficial insects.

Smells good, feels good: oviposition of Chrysoperla carnea-complex lacewings can be concentrated locally in the field with a combination of appropriate olfactory and tactile stimuli

Larvae of common green lacewings (Chrysoperla carnea species-complex) are important generalist predators, and can serve as valuable biological control agents. Since only larvae are predatory, oviposition is of crucial importance. Recently, a ternary floral bait was described, attractive to females that would then lay their eggs in the vicinity of the baits. Earlier studies have shown that females prefer to lay their eggs on spines and hairs of plants. In the present study, we tested whether the number of eggs laid could be increased by combining chemical, visual and tactile stimuli. Common green lacewings were caught equally well in baited funnel traps covered with white, yellow, fluorescent yellow, light blue or black sheets, showing no preference to any of the colours. In further tests the field effect of the ternary floral bait on the oviposition site choice of common green lacewings was confirmed, as in the absence of the bait only negligible numbers of eggs were recorded on egg-laying plates. In the presence of the ternary floral bait, lacewings laid more eggs on spiny than on smooth surfaces. Removal of previously laid eggs did not affect the number of eggs laid afterwards. Our studies demonstrated that by combining the ternary floral bait and an appropriate spiny surface, oviposition of common green lacewings can be increased and concentrated to a relatively small area. Possible practical applications are discussed.

Flight of mayflies towards horizontally polarised and unpolarised light

Light in the optical environment is not just coloured, but it is polarised. The visual system of many insect species is polarisation sensitive which allows them to use the polarisation pattern of skylight for navigation purposes. There is also increasing evidence that mayflies and other aquatic and semiaquatic insects are able to detect water bodies on the base of the water-reflected horizontally polarised light using it as an environmental cue to detect suitable habitats. In a pilot experiment we constructed and tested light trap pairs emitting unpolarised and horizontally linearly polarised light with the same intensity and spectrum to record potential polarisation-sensitive species from various insect orders. Aquatic insects are assumed to use horizontally polarised light for habitat detection. Thus, we expected that these species will be captured in significantly greater numbers by the trap emitting horizontally polarised light than by the trap emitting unpolarised light. Trappings were carried out at each night from April to October during 2001 and 2002 at two sites in Hungary. One of the trapping sites was at the edge of the flood basin of a river with some smaller ponds. The other trapping place situated in a protected sand dune area scattered with ephemeral alkali lakes. The same mayfly species were collected by the traps emitting polarised and unpolarised light. From the recorded five species four species were caught in greater numbers and more frequently by the trap emitting horizontally polarised light. Caenis horaria and Cloeon dipterum mayflies were attracted significantly stronger to the polarised trap, thus they are likely to use positive polarotaxis in habitat detection. Ephoron virgo and Caenis macrura also showed a tendency for polarotaxis, but they were represented with too low numbers of individuals in the samples to produce significant differences.

Conspecific and Heterogeneric Lacewings Respond to (Z)-4-Tridecene Identified from Chrysopa formosa (Neuroptera: Chrysopidae)

Green lacewings (Chrysopidae) are predators of soft-bodied pest insects and are among the most important biological control agents in crop protection. Chrysopa spp. are of special importance since, unlike most green lacewing species, adults are also predatory. The current study was undertaken in search of Chrysopa formosa compounds with semiochemical activity. Using coupled gas chromatography-electroantennography (GC-EAG), head and thorax extracts of C. formosa elicited EAG responses to a compound subsequently identified by coupled GC/mass spectrometry, microchemistry, chemical synthesis and GC peak enhancement as (Z)-4-tridecene. In field experiments, this compound decreased attraction of adult C. formosa to (1R,4aS,7S,7aR)-nepetalactol and that of Chrysoperla carnea species-complex to a ternary floral lure, with the inhibitory effect found to be dose-dependent. Our results suggest that (Z)-4-tridecene may serve as a general warning signal among multiple green lacewing species. Perspectives for potential practical applications are discussed.