The winter moth, Operophtera brumata L. (Lep., Geometridae), on apple and cherry: spatial and temporal aspects of recolonization in autumn

Abstract

The behaviour of adult winter moths Operophtera brumata (L.) (Lep., Geometridae) was investigated during the period of recolonization of fruit orchards in late autumn. Experiments were run simultaneously on both apple and cherry trees in order to detect differences and similarities on these two host plants. The study aimed at a better understanding of spatial and temporal aspects of recolonization of host plants and hence an improvement of monitoring methods.1. Male flight and female migration coincide well enough to guarantee reproductive success. Recolonization of apple and cherry trees occurs simultaneously, but is delayed with decreasing altitude. 2. Male flight activity starts at sunset and reaches its maximum 2 h later. During the night activity decreases gradually to a minimum at sunrise. 3. Females approach tree trunks covering more than 3" of the horizon. The dark part of the horizon appears to be the preferred crawling direction. The travelling time ranges from 1-10 days. 4. Within the tree crown the crawling paths of females are different on cherry and on apple. However, females preferably seek the top segment for oviposition on both cherry and apple trees. 5. On both cherry and apple significantly higher egg densities are found in the top part of the tree crown than in the lower parts. Older wood appears to be more attractive for oviposition probably due to better hiding places. Females seem to optimize between protection and access to food resources for their progeny.The implications of the results for winter moth monitoring in Swiss fruit orchards are discussed.

Phenological variation as protection against defoliating insects: the case of Quercus robur and Operophtera brumata

“…If there is large phenological variation in budburst times of neighbouring trees, hybridisation between adults originating from different trees can lead to significant phenological asynchrony and lowered fitness of offspring as well as lowered fecundity of the local moth population. In addition, adult females of O. brumata are non-selective in terms of their oviposition site (Graf et al 1995;O.-P. Tikkanen, personal observation). Therefore, accidental choices of "incorrect" host trees by adults are unavoidable and increase in numbers as the diversity and the stem density of stands increase.…”

“…6), we can estimate that if a certain genotype is locally adapted to budburst of the tree where its parents have dwelled, 90% of the offspring emerge during the time when the predicted average fitness is high (between 1 and 0.75). This may be one reason why successive generations of adults of O. brumata tend to stay in the vicinity of their pupation site (Graf et al 1995;Van Dongen et al 1996). After all, individual mature Q. robur trees are reasonably stable patches for O. brumata.…”

“…Larvae are likely to pupate near the base of the host tree (Embree 1965). Adult females are flightless and tend to climb up to the nearest tree trunk to copulate and lay eggs (Graf et al 1995). Adult males also remain in a relatively small area (Van Dongen et al 1996).…”

Growth and development of a generalist insect herbivore, Operophtera brumata , on original and alternative host plants

“…Tikkanen, unpublished work). Females climb up on the trunks of trees growing near their place of pupation to mate and to lay eggs (Graf et al 1995). Females usually mate only once, while the males can copulate several times during their life (Van Dongen et al 1998 and references therein).…”

Phenological asynchrony between herbivorous insects and their hosts: signal of climate change or pre-existing adaptive strategy?

“…Among oaks at Wytham studied by Varley & Gradwell, there was very clear association between timing of budburst and subsequent density of feeding larvae: the oaks that waited longest to burst their buds suffered the lowest rates of attack (Hunter et al 1997). Because a wingless female winter moth is likely to climb the same tree from which she descended as a larva (Graf et al 1995) and because the males do not move far (van Dongen et al 1997), it is possible for the moths to evolve local adaptation, such that earlier egg-hatch occurs on earlier-leafing trees. There is evidence that this has indeed occurred both with respect to variation among individual oak trees with differing times of budburst (van Dongen et al 1997) and among tree species (Tikkanen et al 2006).…”