Adult female and neonate larval plant preferences of the generalist herbivore, Epiphyas postvittana

Abstract

The polyphagous leafroller moth, Epiphyas postvittana, is a pest of many fruit crops in New Zealand. Since the larva is highly mobile, host selection in this insect may involve both the adult female and the larva. In order to test the relative importance of the adult female and the neonate larva in the selection of host plants, the ovipositional preferences of females, and the preferences or acceptances of neonate larvae towards 26 plant species, consisting of 15 plants considered hosts and 11 not considered hosts, were investigated. In the ovipositional tests, the mean preferences of females for hosts and non‐hosts were very similar. In contrast, larvae showed a significantly greater mean preference or acceptance towards hosts than to non‐hosts, in both choice and no‐choice bioassays, respectively. There were highly significant correlations between the preferences and acceptances of larvae for plants in the choice and no‐choice tests. In the no‐choice tests, there was a highly significant correlation between the acceptances of neonate larvae towards plants after one and three days (i.e., acceptances changed little over time). Moreover, in these no‐choice tests, there was a significant negative correlation between larval acceptance at 1 day and larval mortality after 3 days; that is, the less acceptable a given plant at 1 day, the more likely larvae would fail to establish, feed, and survive on it by three days. Female and larval preferences towards the various plants were also negatively correlated. Together, these data suggest that the selection of a plant for the neonate larva to feed on is largely governed by the preferences of the larva, rather than by the preferences of the female. However, selection of a plant for oviposition by the female, may be important in host selection for reasons unrelated to larval preferences, for example, by encouraging dispersal, perhaps to other plant species, of the neonate larvae and thereby decreasing intersibling competition.

Bioassays for measuring the resistance of different apple cultivars to the development of leafrollers (Lepidoptera: Tortricidae)

“…Less discrimination by ovipositing females may be compensated by the ability of larvae to move to new host plants in the vicinity, if the host plant proves unsuitable. This is supported by the results of Foster & Howard (1999) who reported very similar oviposition by LBAM on host and non-host plants; they suggested from these and larval studies that plant selection was largely determined by larval behaviour rather than female oviposition. Green (1984) presented evidence of high dispersal of BHLR larvae from 'Dougherty' in the field after they had initially spun shelters on the leaves.…”

“…The initial settlement and feeding of larvae on a novel or non-host plant (e.g., Foster & Howard 1999) or cultivar (Wearing 1998) could test its suitability as a host and determine whether the larvae would remain and develop. Larval dispersal ability combined with a wide host range would provide a safety mechanism to reach an alternative host if the initial plant used by the ovipositing female proved unsuitable.…”

Evaluation of <I>Ostrinia nubilalis</I> (Lepidoptera: Crambidae) Neonate Preferences for Corn and Weeds in Corn

“…Many host preference studies with adult females suggest that females discriminately oviposit on suitable hosts (Courtney et al 1989, Thompson andPellmyr 1991). However, recent studies suggest female oviposition of some Lepidoptera is less discriminatory than assumed (Bernays and Chapman 1994) and is inßuenced by several factors (e.g., landscape and plant availability) (Foster andHoward 1999, Zalucki et al 2002). Thus, understanding neonate host preference has become more important.…”

On-Plant Larval Movement and Feeding Behavior of Fall Armyworm (Lepidoptera: Noctuidae) on Reproductive Corn Stages

“…Once the larvae are on a suitable host they will usually settle and establish a feeding site (Chang et al 1985, Hochberg 1987, Varela and Bernays 1988, Therry et al 1989, Khan et al 1996, Foster and Howard 1999, Zalucki et al 2002. Overall, the highest concentration of larvae was observed in the ear zone from the second to the last evaluation, independent of corn stage (Table 3; Figure 1).…”

“…According to the literature (Zalucki et al 1986(Zalucki et al , 2002, during the exploration for a suitable feeding site, if larvae probe the substrate and recognize the host or plant part is unsuitable, then exploration is likely to continue (Chang et al 1985, Hochberg 1987, Varela and Bernays 1988, Terry et al 1989, Khan et al 1996, Foster and Howard 1999, Zalucki et al 2002.…”