Theresa L Pitts-Singer1, James D Barbour2. 1. USDA ARS Pollinating Insects Research Unit, Logan, UT, USA. 2. University of Idaho, Parma Research and Extension Center, Parma, ID, USA.
Abstract
BACKGROUND: The chitin synthesis inhibitor novaluron can suppress pests that affect alfalfa seed production, but can negatively affect reproductive success in the alfalfa pollinator Megachile rotundata. Novaluron is considered to be a reduced-risk insecticide because it disrupts ecdysis and is non-lethal to adult insects, but some exposed adults have fewer eggs and suppressed egg hatch. For this experiment, bees nested in field cages where they were exposed to alfalfa that had never been treated with novaluron, alfalfa that had recently been sprayed or alfalfa that had been sprayed 1 and 2 weeks earlier. RESULTS: Compared with the control, greater proportions of dead eggs and larvae and lower proportions of live prepupae occurred when bees were exposed to recent novaluron sprays as well as one- or two-week old spray residues. Two possible routes of residual pesticide exposure were revealed. Mother bees become contaminated through ingestion or direct contact, or pollen-nectar provisions become contaminated with novaluron (1) on or within leaf pieces that surround provisions or (2) transferred from mother bees' bodies to provisions. CONCLUSION: We found strong immature mortality effects of novaluron and its residues on M. rotundata. Understanding all possible pesticide exposure routes for pollinating bees enhances decision-making for maintaining bee populations while protecting crops.
BACKGROUND: The chitin synthesis inhibitor novaluron can suppress pests that affect alfalfa seed production, but can negatively affect reproductive success in the alfalfa pollinator Megachile rotundata. Novaluron is considered to be a reduced-risk insecticide because it disrupts ecdysis and is non-lethal to adult insects, but some exposed adults have fewer eggs and suppressed egg hatch. For this experiment, bees nested in field cages where they were exposed to alfalfa that had never been treated with novaluron, alfalfa that had recently been sprayed or alfalfa that had been sprayed 1 and 2 weeks earlier. RESULTS: Compared with the control, greater proportions of dead eggs and larvae and lower proportions of live prepupae occurred when bees were exposed to recent novaluron sprays as well as one- or two-week old spray residues. Two possible routes of residual pesticide exposure were revealed. Mother bees become contaminated through ingestion or direct contact, or pollen-nectar provisions become contaminated with novaluron (1) on or within leaf pieces that surround provisions or (2) transferred from mother bees' bodies to provisions. CONCLUSION: We found strong immature mortality effects of novaluron and its residues on M. rotundata. Understanding all possible pesticide exposure routes for pollinating bees enhances decision-making for maintaining bee populations while protecting crops.
Authors: Ju-Mi Hwang; Jeong-Won Bae; Eun-Ju Jung; Woo-Jin Lee; Woo-Sung Kwon Journal: Int J Environ Res Public Health Date: 2021-12-22 Impact factor: 3.390