Determining the Impact of northern and southern strains of plum curculio on Interstate Shipment of Virginia Apples
PI(s): Pfeiffer, Douglas G
Investigators: Zhang, Xing
Website: Plum curculio @ Va Fruit Web Site
Abstract: This project attempts to differentiate univoltine and bivoltine southern strains of plum curculio based on biochemical methods, and determination of the within-state distrbution of the two strains. The presence of second-brood larvae in the fruit at harvest will complicate shipment of fruit to certain states and countries.
Description:
There are northern and southern strains of plum curculio. The northern strain
is marked by an obligatory winter diapause, and is therefore univoltine. The
southern strain has no such obligatory diapause; there are two generations
annually and it can breed continuously in culture. When northern females are
mated to southern-type males, there is lower fecundity and fertility than in
the reciprocal cross (southern females and northern males). Even in the latter
cross, there is reduced oviposition and egg hatch (Padula & Smith 1971). The
reduced oviposition was associated with early degeneration of the
spermatophore within the spermatheca. Chapman (1938) presented the approximate
distribution of the two strains. The dividing line runs northeast to southwest
through the western portion of Virginia. Bobb (1952) reported a single brood
in the Shenandoah Valley of Virginia, with a second in the Piedmont. However,
the situation may not always be clear. Bobb (1973) reported two broods from
the Coastal Plain of Virginia and only a partial second in the Piedmont,
implying a climatic effect. Stearns (1931) reported a single brood in northern
and central Delaware, and a partial second in the southern part of the state.
The distribution of the strains is important for several reasons. From
an IPM viewpoint, the need for additional sprays will depend on the presence
of ovipositing females later in the season. The presence of a second
generation greatly increases the likelihood of larval presence in the fruit at
harvest. This has bearing in developing export markets. For the past two
years, California has questioned the importation of Virginia and Delaware
apples because of the possibility of larval infestation in the late summer.
Documentation of the status of the bivoltine strain would clarify the need for
such concern.
Commodities: Apples, Peaches
Resources: Virginia Fruit Web Site
Disciplines: Ecology, Horticultural Systems, Integrated Pest Management, Physiology, Sustainable Agriculture, Systematics
Audiences: Commodity Groups, Extension Agents, Government Agencies, Graduate Students, Researchers
