Plant volatiles mediate host finding in insect herbivores and lead to host fidelity and habitat‐specific mating, generating premating reproductive isolation and facilitating sympatric divergence. The apple fruit moth, Argyresthia conjugella Zeller (Lepidoptera: Argyresthiidae), is a particularly suitable species to study the cues and behavioural mechanisms leading to colonization of a new host: it recurrently oviposits on the non‐host plant, apple Malus domestica Borkh. (Rosaceae), where the larvae cannot complete their development. The larval host of the apple fruit moth (Lepidoptera, Argyresthiidae), is rowan Sorbus aucuparia L. (Rosaceae). Fruit setting in rowan, however, fluctuates strongly over large areas in Scandinavia. Every 2–4 years, when too few rowanberries are available for egg laying in forests, apple fruit moth females oviposit instead on apple in nearby orchards, but not on other fruits, such as pear or plum. This poses the question of which cues mediate attraction to rowan and apple, and how apple fruit moth discriminates rowan from apple. Chemical analysis and antennal recordings showed that 11 out of 15 rowan volatiles eliciting an antennal response in A. conjugella females co‐occur in rowan and apple headspace, in a different proportion. In the field, A. conjugella was attracted to several of these plant volatiles, especially to 2‐phenyl ethanol, methyl salicylate, and decanal. Addition of anethole to 2‐phenyl ethanol had a strong synergistic effect, the 1 : 1 blend is a powerful attractant for A. conjugella males and females. These results confirm that volatiles common to both plants may account for a host switch in A. conjugella from rowan to apple. Some of the most attractive compounds, including 2‐phenyl ethanol, anethole, and decanal, which have been found in several apple cultivars, were not present in the headspace of the apple cultivar, Aroma, which is also susceptible to attack by A. conjugella. This supports the idea that the odour signal from apple is suboptimal for attraction of A. conjugella, but is nonetheless sufficient for attraction, during times when rowan is not available for egg laying.

Masting of rowan Sorbus aucuparia L. has been studied in 45 sites in southern Norway for 22 years. We present data on the year‐to‐year variation in fruit setting of rowan, and show that masting is spatially synchronous in Norway and probably all over Fennoscandia. The apple fruit moth Argyresthia conjugella Zeller is an important seed predator on rowan. We present data on the abundance of apple fruit moth in rowanberries during these years and discuss the consequences of masting and intermasting of rowan for apple fruit moth as a pest of apple. We conclude that growth and climate have little impact on flowering intensity and suggest that masting of rowan is an adaptive defense against seed predation and a new example of predator satiation: intermast years inhibit predators and prepare the rowan for the subsequent mast.

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 beta-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.

-Apple fruit moth Argyresthia conjugella is a specialist seed predator of rowan et al. -p. 2 (11)

Black cherry aphid [Myzus cerasi (Fabricius)] and cherry fruit moth [Argyresthia pruniella (Clerck)] are the main insect pests on sweet cherries in Norway. In this study, application of rapeseed oil alone and rapeseed oil mixed with pesticides were tested as a control method against overwintering eggs of both black cherry aphid and cherry fruit moth. Results showed that rapeseed oil applied at the late dormant stage significantly reduced damage by black cherry aphid. Efficiency of oil mixed with pesticides was higher, but only significant in three of seven trials. The efficiency of rapeseed oil against cherry fruit moth was low compared with what was achieved for black cherry aphid, but within the range that has been reported for other botanical pesticides. As for the black cherry aphid, adding pesticides to oil decreased damage by the cherry fruit moth. Timing of treatment and effect of temperature were discussed.