Thrips were sampled from six nectarine orchards in the Dry Central Interior, British Columbia, Canada, between April and June 1993 using yellow sticky cards on posts spaced around the perimeter of each orchard. Although 12 identified species of thrips were captured, >90% of individuals were the western flower thrips, Frankliniella occidentalis (Pergande). The flight patterns and abundances of western flower thrips were compared between orchards located in two differently oriented valleys (N-S and E-W) and between orchards located close to or far from areas of wild land. Results indicate that densities of western flower thrips entering orchards, and their direction of movement, were related more to the external vegetation than either location within the two different valleys or general wind flow patterns. Western flower thrips tended to move into orchards close to ground level in early spring (late April and early May) but flew higher as ground cover grew taller and temperatures increased. Densities of western flower thrips at ground level were highest in an orchard with the densest dandelion ground cover. We conclude that the location of nectarine orchards in relation to wild areas is a major determinate of western flower thrips densities.

Development of a control strategy for thrips attacking nectarine trees depends on an understanding of their phenology, distribution, and life history as related to characteristics of nectarine orchards. To this end, we compared the overwintering behavior, distribution, and abundance of western flower thrips, Frankliniella occidentalis (Pergande), among 11 nectarine orchards located in the dry central interior of British Columbia, Canada, during 1993 and 1994. Western flower thrips emerged from areas not previously used for agriculture (wild areas) and from within orchards before trees were out of dormancy. Flight of thrips within and around orchards peaked during early bud development, with a second major peak several weeks later after husk fall as the next generation emerged. Orchards protected from wild areas by other orchards had the lowest densities of thrips in buds. Density estimates of western flower thrips on trees were not affected by location of trees within orchards or buds within trees, but most thrips were found in the most developed buds on a tree at any one time. Thrips were not found within buds until petal was first visible on the buds. Larval feeding on buds at early petal fall resulted in serious surface russetting of fruit.

Hourly flight patterns of western flower thrips, Frankliniella occidentalis (Pergande) (Thysan., Thripidae) were assessed over a 24 h period in two nectarine orchards located in the Similkameen Valley, British Columbia, on 13 separate occasions between March and October 1994. The numbers of western flower thrips (male or female, dark or pale morphs) trapped per hour at between four to eight heights (0.25–2.00 m) were compared with temperature, wind speed, time of year and location of trap placement. Traps were placed within orchards, at the border of orchards and adjacent wild land, and within wildlands. Temperature and wind speed thresholds are defined, although the effect of wind speed varied with height of flight. Height of flight was affected by both the height of prevalent vegetation and temperature, with mean height of flight increasing linearly with temperature. Numbers of thrips in flight decreased with height of sticky trap from the ground. The pale morph was generally more common than the dark morph of western flower thrips. Males were not present until after emergence of the first generation in May, and were found at an approximate ratio of 4 : 1 (F : M) for the rest of the year. There were no differences between sexes or morphs of western flower thrips for location, height or daily patterns of flight.

The phenology of damage by the western flower thrips, Frankliniella occidentalis (Pergande), on nectarines was investigated using sticky cards and direct sampling of buds between 1993 and 1995 in the interior of British Columbia, the most susceptible period for damage by western flower thrips to nectarines. The life stage responsible for damage and variation in susceptibility to damage of 11 different nectarine varieties were determined. To evaluate the predictive ability of 2 sampling methods, thrips were counted from both buds and sticky cards before petal fall and correlated to damage levels at husk drop. Damage to nectarines was caused almost entirely by larval feeding at petal fall. No predictive relationships between adult or larval densities of western flower thrips and subsequent damage to fruit were apparent. Varieties did not differ in terms of larval densities at petal fall or the subsequent damage to fruit. Female western flower thrips oviposit in nectarine buds from dormant through bloom stages primarily in sepal tissues in the early buds, and in filaments and petals as these become available.

1. This study compared the roles of pupal mortality and parasitism in winter moth (Operophtera brurnata) population dynamics in Nova Scotian apple orchards and assessed the importance of beetles as pupal predators.2. The component of pupal mortality termed predation accounted for greater stage-specific mortality of winter moth than parasitism by Cyzenis albicans in four neglected orchards.3. Parasitism by Cyzenis albicans was not spatially density-dependent in any orchard, whereas the predation component of pupal mortality was spatially density-dependent in the two orchards most densely populated by winter moth.4. Field experiments indicated that over 60% of pupal predation may be attributed to beetles, and that about 46% of pupal predation occurred within 4 weeks after pupal drop. .Mortality of introduced populations of winter moth in Nova Scotia resembles that of native populations in England where density-dependent predation regulates the winter moth population and reduces the parasitoid population to minimal levels. The situation in Nova Scotia appears to have changed appreciably since the establishment of parasitoids into the system in the 1950s.