Aerial powdering of bees inside mobile cages and the extent of neonicotinoid cloud surrounding corn drillers

Abstract

Sudden losses of bees have been observed in spring during maize sowing. The death of bees has been correlated with the use of neonicotinoid-coated seed and the toxic particulates emitted by pneumatic drilling machines. The contamination of foragers in flight over the ploughed fields has been hypothesized. The airborne contamination has been proven, both with bees inside fixed cages around the field and in free flight near the driller. A new trial involving mobile cages has been established and consists of making rapid passes with single bees inside cages fixed to an aluminium bar. The bar was moved by two operators at different distances from the working drilling machine. A single pass was shown as sufficient to kill all the bees exposed to exhaust air on the emission side of the drill, when bees were subsequently held in high relative humidity. The extent of toxic cloud around driller was evaluated at the height of 0.5, 1.8 and 3.5 m and proved to be about 20 m in diameter, with an ellipsoidal shape. The shape may be influenced by working speed of the drill and environmental parameters, and is easily shown by adding talc powder to the seed in the machine hopper. A new driller equipment was evaluated consisting of two tubes inclined towards the soil that direct the exhaust air towards the ground. The survival rate of the bees was not substantially increased using the modified drill and was lower than 50%. Chemical analyses show up to 4000 ng of insecticide in single bees with an average content around 300 ng. Similar quantities were observed at increased distances from the modified or unmodified drillers. This new evaluation of bee mortality in the field is an innovative biological test to verify the hypothetical efficiency (or not) of driller modifications

UHPLC-DAD method for the determination of neonicotinoid insecticides in single bees and its relevance in honeybee colony loss investigations

“…Corn sowing using pneumatic drilling machines and seeds coated with neonicotinoids (an agricultural practice used worldwide) release into the atmosphere large amounts of coating particles that are efficiently intercepted by foraging bees flying over the sowing fields [11,12,21,25,26]. Bees exposed to these toxic particles show characteristically acute effects, with a short-term mortality which compares well with the colony loss phenomena observed by beekeepers in spring, and associated with corn sowing.…”

“…In this connection, Girolami and coworkers have recently proposed two novel routes of exposure to and intoxication with neonicotinoids which may justify such a sudden spring mortality: the translocation of a significant amount of neonicotinoids from the coated seed to the guttation drops of young corn plants [6,24] and the direct powdering with neonicotinoid-containing particles of foraging bees in free flight accidentally crossing the sowing fields [11,21,25,26].…”

Potential external contamination of pneumatic seed drills during sowing of dressed maize seeds

“…These last results are in line with those obtained in other studies using the same tracer 10 and using the chemical product (seeds treated with neonicotinoids). 15,17,22 When a seed drill is used in its standard configuration, an important role is played by the direction in which the air exits the fan. In fact, in this experiment, greater tracer deposits on drill frames were obtained with a lateral air direction.…”

“…17 Some of the dust particles released in the airstream from the fan may also be deposited on the machine's external surface, becoming dangerous for the environment (point-source pollution) and for operators, similar to those dangers present when pesticides are applied with sprayers. 18 In fact, potential point-source environmental contamination can be observed in the area used to wash the seed drill at the end of the sowing season before its storage or in the outdoor parking area on account of rainfall.…”

An update of the Worldwide Integrated Assessment (WIA) on systemic insecticides. Part 1: new molecules, metabolism, fate, and transport

“…The release into the atmosphere of particulate matter containing insecticides causes the contamination of vegetation surrounding the field, with the consequent exposure of nontarget animals to sublethal dose of insecticides (Greatti et al 2006;Stewart et al 2014). Furthermore, these abraded particles pose a serious risk to insects (in particular foraging bees and other pollinators) flying across the field during sowing operations (Girolami et al , 2013Marzaro et al 2011). Since then, attention has been paid to the reduction of particulate matter expulsion using modified drilling machines fitted with devices in order to reduce particulate emissions and proper handling of coated seeds (Biocca et al 2017;Manzone et al 2015;Manzone and Tamagnone 2016;Pochi et al 2015a, b).…”