Field experiments with the pollinator species, Osmia lignaria propinqua Cresson (Hymenoptera: Megachilidae) in Apple Orchards: III, 1977 Studies (1984)

This study tested the technique for releasing adult Osmia lignaria propinqua Cresson bees from natal nests placed in an isolated apple (Malus sylvestris Mill.) orchard. In addition, 5 nest materials were placed into each of 22 nest shelters located centrally in the orchard to determine their comparative attractiveness to nesting bees. Results obtained clearly demonstrated that: nest holes from which bees emerged were more attractive to nesting females than larger numbers of adjacent new holes; levels of attractivity to different nest materials were expressed consistently between shelters, with milk cartons least attractive and drilled holes in wood most attractive; and the number of nests or cells constructed/shelter was nearly equal. The bee population released in this orchard was increased by 240% after one generation. This increase was attributed primarily to those particular management practices tested. The first introduction of Osmia lignaria propinqua Cresson into an apple orchard was made in 1974 to determine its potential as a pollinator for that crop (Torchio, 1976). This native bee species has since been tested successfully as an orchard crop pollinator (Torchio, 1979), and more recent studies have emphasized development of management practices for commercial-sized populations of O. propinqua bees in orchard environments (Torchio, 1981a, b, 1982a-c). Results obtained from those studies have shown that nesting success of O. propinqua bees established in orchards can be influenced by predictive behavioral responses to: methods employed in their release, types of nest materials used, and the placement design of nest traps within orchards. One study (Torchio, 1982c) clearly demonstrates that prenesting O. propinqua bees emerged from natal nests (N-N) do not disperse as readily as mass-released populations (M-R). As a consequence, the ratio of bees nesting compared to numbers of bees released was higher in the N-N orchard and lower in the M-R orchards. While nesting was successful in all four apple orchards, the highest rate of nesting success was found in the N-N orchard. That particular orchard experiment was, however, a preliminary study where minumum numbers of bees and nest materials were used due to limitations of supplies and materials. A second, more comprehensive study was therefore designed to answer several questions derived from results obtained in the N-N orchard experiment: (1) Do dispersal patterns of O. propinqua bees emerged from natal nests in orchards vary when population sizes are increased? (2) Can nesting success be enhanced when the number of available nesting holes per female is increased? (3) If filled nests (paper soda straws containing cells of O. propinqua bees) are inserted into a variety of nest materials placed in an orchard, will emerging bees continue to establish nests in preferred nest materials? Results obtained in the expanded study are reported below. methods and materials: The O. propinqua bees used in this study were derived from nest trap materials placed in local canyons during the previous year. After these traps were returned to the laboratory, sample numbers of nests (500) were dissected to determine sex ratio (1.6866:12) and the average number of live bees/nest (3.4). The remaining nests (paper soda straws, 7 mm in diameter, inserted into holes drilled in various materials) were removed from nest blocks during September and placed in a 3?C temperature cabinet on October 1. These nests were transferred to a 27?C incubator in late April for 3 days (until the first males emerged) and each was then inserted into appropriate nest traps that were subsequently transferred to the experimental orchard. All nest traps were returned to the laboratory on May 29, the day following disappearance of apple bloom in the orchard. Nests were dissected and data were recorded during September of the same year. The 2.63-hectare orchard used in this study was located 3.2 km NE of Logan, Cache Co., Utah on the western bench of the Wasatch mountains. Twenty-two, plywood, military footlockers (each 81.3 cm x 43.2 cm x 30.5 cm) were used as nest shelters, and each was attached to metal fence posts (Torchio, 1982c) to face SE. All nest shelters were established in the center of the orchard and each was placed between trees in 4 adjacent rows. An additional shelter was then added to house a Belfort? This content downloaded from 157.55.39.35 on Thu, 01 Sep 2016 05:27:09 UTC All use subject to http://about.jstor.org/terms 518 JOURNAL OF THE KANSAS ENTOMOLOGICAL SOCIETY Table 1. Nest materials and numbers of nest holes/shelter placed in 22 shelters in an apple orchard to study nest patterns established by Osmia lignaria propinqua females (1977). No. holes No. traps No. holes No. total Nest material per trap per shelter per shelter nest holes Milk cartons 23 4 92 2024 Wood grooves 36 1 36 792 Styrofoam 40 2 8