Evaluating a filtering and recirculating system to reduce dust drift in simulated sowing of dressed seed and abraded dust particle characteristics.

BACKGROUND: The pneumatic precision drills used in maize sowing can release dust owing to abrasion of dressed seed; the drift of dust containing insecticide active ingredients is harmful to honey bees. Therefore, we developed a device for drills that uses partial recirculation and filtration of the air by means of an antipollen and an electrostatic filter. RESULTS: Tests were carried out by simulating the sowing of seed treated with imidacloprid, thiamethoxam, clothianidin and fipronil. Dust released by the drill in different configurations was analysed to assess its mass and active ingredient concentration, size distribution and particle number concentration. In general, particles with a diameter smaller than 2.5 and 10 µm represent about 40 and 75% of the total dust mass respectively. The finest size fraction (<1 µm) contains a higher content of active ingredient. The prototype equipped with both antipollen and electrostatic filters always showed a reduction in dust emission greater than 90% in terms of both total mass and active ingredient amount, with a greater efficiency in the reduction in particles below 4 µm. CONCLUSION: This study presents an engineering solution addressing dust losses during sowing, contributes to the description of abrasion dust fractions and provides suggestions for further development of the prototype. © 2016 Society of Chemical Industry.

Potential exposure of bees, Apis mellifera L., to particulate matter and pesticides derived from seed dressing during maize sowing.

This paper assessed the potential exposure of bees (Apis mellifera L.) to pesticides during maize (Zea mays L.) sowing with pneumatic drills. Data were derived from tests carried out in field tests, comparing two configurations of a pneumatic precision drill: conventional drill; drill with air deflectors. In addition, static tests simulating the sowing under controlled conditions, were performed on the drill equipped with an innovative system developed at CRA-ING. During the field tests, the concentrations in the air of the active ingredients of four insecticides used in maize seed dressing (imidacloprid, clothianidin, thiamethoxam and fipronil) were recorded. The concentrations of active ingredients in the air were used for assessing the quantities of active ingredients that a bee might intercept as it flies in a sort of virtual tunnel, the dimensions of which were dependent upon the bee body cross-section and the length of flight. The results of the field tests show that the air deflectors were not completely effective in reducing the amount of active ingredients dispersed in the air. The results of the static tests with drill equipped with the prototype indicated reductions of the active ingredient air concentrations ranging from 72 % up to 95 %, with reference to the conventional drill. Such ratios were applied to the amounts of active ingredients intercepted by the bees in the virtual tunnel contributing to a consistent reduction of the probability that sub-lethal effects can occur.

Sowing simulation tests of a pneumatic drill equipped with systems aimed at reducing the emission of abrasion dust from maize dressed seed.

The utilization of dressed seed for spring sowing is a widespread practice to control some pests with reduced doses of chemical products. However some insecticides employed in maize seed dressing, namely belonging to the neonicotinoid family and fipronil, have been claimed to play a role in the decline of honeybees (Apis mellifera L.). Pneumatic drills used in maize sowing are charged with contributing to the dispersion of the abrasion dust produced by dressed seeds, favoring the contamination of the honeybee habitat. Different devices similar to air deflectors have been introduced on pneumatic drills in order to reduce dust drift. During previous field tests carried out by the authors during recent years reduction of dust concentration both in the air and at soil surface has been shown as a consequence of their application. As field tests are affected by the variability of environmental parameters (namely wind speed and direction) the results are not always reliable, comparable and of a general validity. This paper refers to a sowing simulation test system in which pneumatic drills can be tested at a fixed point under controlled conditions of the main environmental parameters. In the test area, protected by external influences, artificial wind conditions are created by means of a fan. The drill, suitably placed in the test area, operates the seed distribution "sur place" by means of an electric engine connected to the drill's driving wheel. A 22.5 m long sampling area, leeward with respect to the drill position, has been identified. Along the sampling area a series of Petri dishes has been placed, with the aim of capturing the depositing dust and providing the concentration of the active ingredients (a.i.) at ground level. At the same time, three air samplers with PTFE diskette filters have been used for the detection of the a.i. The test system has been used for the test of a pneumatic drill, equipped with and without air deflectors, using maize seed dressed with four a. i. (imidacloprid, clothianidin, thiametoxam, fipronil). The results showed regularly decreasing of the concentrations as distance increased, both in the air and at ground level. Moreover, the difference determined by the adoption of the drift reducing device (air deflectors) resulted clear and it can be quantified at around 50 % of the a.i. amounts observed without deflectors. Finally, the paper proposes a data processing method that, from the values observed at fixed point, provides the theoretical a.i. concentration behavior that would occur in field, under the same conditions of wind speed and direction and working speed. The obtained results are coherent with previous field test.

Preliminary study on persistence in soil and residues in maize of imidacloprid.

The aim of this work was to study the distribution of imidacloprid in soil and its translocation to roots and aerial parts of maize plant. The main objective was to assess imidacloprid residues in field environment, in order to provide data on honeybees exposure level to such an active substance. Imidacloprid has been detected and quantified by Triple Quadrupole HPLC-MS-MS. Pesticide persistence in the soil and its residues in pollen and in maize plants have been evaluated during the growing of maize plants developed from seeds dressed with Gaucho 350 FS (imidacloprid: 1.0 mg/seed). The sowing has been performed by means of a pneumatic precision drill. Samples have been collected at 30, 45, 60, 80, 130 days after the sowing, as pollen samples have been collected at the tasseling. Imidacloprid presence in aerial part of maize plant declined to 2-3 µg/kg 80 days after the sowing, while concentration in kernel at harvest was <1 µg/kg. Maize pollen represents an important part of protein supply of beehives, and it is of critical importance to bee foraging. The values detected (imidacloprid residues <1 µg/kg) showed that maize pollen source should not be relevant for acute toxicity impact on honey bees.