Effects of eco-friendly flower thinning formulations on a pollination insect, apis mellifera

Flower thinning is necessary for crop production in various orchards. The effects of various ingredients of Koduri-Plus, an eco-friendly flower thinning formulation (FTF), were determined on the major pollination insect Apis mellifera. Three different FTFs, a mixture of 0.7% zinc and 1.5% manganese (A), a mixture of 0.7% zinc and 2.0% boron (B), a mixture of 2.0% seaweed extract (C), and lime sulfur solution were examined by measuring the contact and oral toxicities against adult worker bees. Both direct spray and oral ingestion of all three 1% FTF solutions did not cause any lethal effects for workers based on 72 h observation, but treatment with 1% lime sulfur solution increased worker mortality. Oral ingestion of FTF A and FTF C did not inhibit acetylcholinesterase (AChE) activity of workers at 24 h after treatment, but was slightly decreased by FTF B treatment. However, oral ingestion of the organophosphate pesticide dichlorvos or lime sulfur solutions significantly inhibited AChE activities. Our results suggest that manganese and seaweed extract of FTFs were not toxic for honeybees, in terms of contact and ingestion. Therefore, newly developed FTFs can be used to improve flower thinning activity without any detrimental effects on pollinating insects.