TY - JOUR AU - Long, Rachael AU - Morandin, Lora TI - Low hybrid onion seed yields relate to honey bee visits and insecticide use JF - California Agriculture JO - Calif Agr Y1 - 2011/07/01 VL - 65 IS - 3 SP - 155 EP - 159 PB - University of California Agriculture and Nature Resources SN - 0008-0845 UR - http://dx.doi.org/10.3733/ca.v065n03p155 L3 - 10.3733/ca.v065n03p155 AB - Onion thrips, previously considered of minor importance to hybrid onion seed production in California, vector the newly introduced iris yellow spot virus, a serious pathogen of onions that can cause significant yield losses. Insecticide use to control onion thrips has increased in onion seed fields, coincident with a steep decrease in yields, especially in Colusa County. We examined a number of possible contributing factors and found a strong positive correlation between honey bee activity and onion seed set, indicating that a lack of pollination may be contributing to the reduced yields. In addition, honey bee visits to onion flowers were negatively correlated with the number of insecticides applied per field and field size. Reduced onion seed yields in recent years could be associated with the increase in insecticide use, which may be repelling or killing honey bees, important pollinators of this crop.