Effects of the insecticide phosmet on solitary bee foraging and nesting in orchards of Capitol Reef National Park, Utah (U.S.A.)

Authors: ALSTON, D. - USU, BIOLOGY, LOGAN,UT; TEPEDINO, V. - ARS/RETIRED,LOGAN,UT; BRADLEY, B. - JUNIATA COLLEGE; TOLER, T. - HDR ENGINEERING, SLC,UT; Griswold, Terry

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/23/2007
Publication Date: 8/13/2007
Citation: Alston, D.G., Tepedino, V.J., Bradley, B.A., Toler, T.R., Griswold, T.L. 2007. Effects of the insecticide phosmet on solitary bee foraging and nesting in orchards of Capitol Reef National Park, Utah (U.S.A.). Environmental Entomology. 36(4): 811-816

Interpretive Summary: Capitol Reef National Park, south-central Utah, USA, contains 22 small managed orchards planted with antique fruit varieties by Mormon pioneers beginning over a century ago. Fruit is harvested by individual users in a pick-and-pay program. Management includes spraying apple and pear trees individually with the insecticide phosmet for the introduced pome fruit pest, codling moth (Cydia pomonella (L.)). The Park is also home to a rich diversity of flowering plants, many of which are rare, bee-pollinated, and have populations within 1 km of the orchards. We studied the short-term effect of phosmet spraying on bee populations over three years, including the effect on bees foraging on native and alien plants within the orchard understory, and adjacent to it; and the effect on bees nesting in, and at several distances from, the orchards. We recorded a rich bee fauna (47 different kinds) in the orchards and on plants nearby. In two years (2002, 2004) we found no difference in the number of native bee visits to several species of plants flowering in and near to orchards immediately before and one day after spraying. Conversely, our nesting studies using the semi-domesticated alfalfa leafcutting bee, Megachile rotundata (F.), showed strong significant declines in the number of adult males, nesting females and in progeny production subsequent to spraying at distances up to 160 m from sprayed orchards where the bees were presumably foraging. Our results show that at least some species of bees are negatively affected by phosmet spraying, and suggest that caution should be exercised in its use in areas where bees are apt to be foraging.

Technical Abstract: Capitol Reef National Park, south-central Utah, USA, contains 22 small managed orchards planted with antique fruit varieties by Mormon pioneers beginning over a century ago. Fruit is harvested by individual users in a pick-and-pay program. Management includes spraying apple and pear trees individually with the insecticide phosmet for the introduced pome fruit pest, codling moth (Cydia pomonella (L.)). The Park is also home to a rich diversity of flowering plants, many of which are rare, bee-pollinated, and have populations within 1 km of the orchards. We studied the short-term effect of phosmet spraying on bee populations over three years, including the effect on bees foraging on native and alien plants within the orchard understory, and adjacent to it; and the effect on bees nesting in, and at several distances from, the orchards. We recorded a rich bee fauna (47 different kinds) in the orchards and on plants nearby. In two years (2002, 2004) we found no difference in the number of native bee visits to several species of plants flowering in and near to orchards immediately before and one day after spraying. Conversely, our nesting studies using the semi-domesticated alfalfa leafcutting bee, Megachile rotundata (F.), showed strong significant declines in the number of adult males, nesting females and in progeny production subsequent to spraying at distances up to 160 m from sprayed orchards where the bees were presumably foraging. Our results show that at least some species of bees are negatively affected by phosmet spraying, and suggest that caution should be exercised in its use in areas where bees are apt to be foraging.