EFFECT OF WINTERING DURATION AND TEMPERATURE ON SURVIVAL AND EMERGENCE TIME IN THE ORCHARD POLLINATOR OSMIA LIGNARIA (HYMENOPTERA: MEGACHILIDAE)

Authors: BOSCH, JORDI - UTAH STATE UNIVERSITY; Kemp, William - Bill

Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2003
Publication Date: 8/1/2003
Citation: Bosch, J., Kemp, W.P. 2003. Effect of wintering duration and temperature on survival and emergence time in the orchard pollinator Osmia lignaria (Hymenoptera: Megachilidae). Environmental Entomology. 32(4):711-716.

Interpretive Summary: We measured winter survival, emergence time and vigor in the blue orchard bee, Osmia lignaria, exposed to various wintering regimes combining 5 durations (30, 90, 150, 210, and 270 days) and 5 temperatures (0, 4, 7, 10, and 13ºC). For all temperatures, survival was highest at 90 d of wintering. Temperatures of 10ºC or higher were unsuitable for wintering O. lignaria populations even for short periods. At 7ºC, bees showed increased mortality, and reduced vigor when wintered for more than 150 days. For long wintering periods (210 or longer), only temperatures of 4ºC or lower were acceptable. Time to emerge following post-wintering incubation decreased with increasing wintering duration and wintering temperature. Managing the activity of O. lignaria to coincide with fruit tree bloom initiation is much more easily accomplished with the use of populations exhibiting short emergence times. Several wintering regimes yielding acceptable survival (150 days at 0, 4 and 7ºC, and 210-270 days at 0 and 4ºC), produced mean emergence times shorter than 5 days. Our results can be used to establish appropriate wintering regimes for O. lignaria populations managed to pollinate orchard crops differing in bloom time (from almonds in February to apples in May), and therefore allowing for shorter or longer wintering periods.

Technical Abstract: We measured winter survival, emergence time following incubation at 20ºC, and longevity following emergence in males of the orchard pollinator Osmia lignaria Say exposed to 25 artificial wintering regimes differing in duration (30, 90, 150, 210, and 270 d) and temperature (0, 4, 7, 10, and 13ºC). For all temperatures, survival was highest at 90 d of wintering. Temperatures of 10ºC and greater were unsuitable for wintering O. lignaria populations even for short periods. At 7ºC, bees showed increased mortality, signs of excessive fat body depletion, and decreased longevity when wintered for greater than 150 d. Wintering periods longer than 210 d required temperatures of less than 4ºC for acceptable survival. Post-emergence longevity was highest when bees were wintered at 0ºC for 210 d. Time to emerge following incubation decreased with increasing wintering duration and wintering temperature, and many bees wintered for long periods at the warmest temperatures emerged before incubation. Managing the activity of O. lignaria to coincide with fruit tree bloom initiation is much more easily accomplished with the use of populations exhibiting short emergence times. Several wintering regimes yielding acceptable survival and longevity (150 d at 0, 4 and 7ºC, and 210-270 d at 0 and 4ºC), produced mean emergence times of 5 d or less. Our results can be used to establish appropriate wintering regimes for O. lignaria populations managed to pollinate orchard crops differing in bloom time (from almonds in February to apples in May), and therefore allowing for shorter or longer wintering periods.