April 1951: Curtailing drifting pesticides

Among them are pesticides, which were becoming widespread in a post-war economy that continued food rationing until 1953.

Since their introduction, however, pesticides have been linked with a decline in biodiversity, notably bee populations; for having negative impacts on air, soil and water, and for being detrimental to human health.

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Less than a decade after the war, it was becoming clear that pesticides had to be applied in a more controlled and targeted manner because they would sometimes drift from their intended target and cause damage to different crops nearby. The Ministry of Agriculture also raised concerns about protections afforded to agricultural workers who were applying these chemicals.

Current regulations from the Health and Safety Executive state: ‘Users of pesticides must ensure that all reasonable precautions are taken to prevent spray drift. Reasonable precautions include using the right spraying techniques and equipment, taking account of weather conditions and the need to protect neighbours’ interests and other members of the public, wildlife and the environment.’

Pest Control Ltd, from Harston, Cambridgeshire, were among the first to pay close attention to the problem of drift in crop spraying and in April 1951 The Engineer reported on field trials of ‘Nodrif’, an engineered solution to the problem.

Led by managing director Dr WE Ripper, the Nodrif boom was employed on the company’s standard ‘Cambridge’ sprayers which had a spray bar 40ft wide and an arrangement that enabled the height of the spray bar to be accurately adjusted.

“The spray bar consists of three sections, each of which has its individual cowl,” said The Engineer. “Both the side booms are supported by castor wheels, which keep the spray bar at a constant distance from the ground and also to prevent the wind shields from digging into the ground. The wind shields themselves are arranged to form a large obtuse angle with the field, so that the wind may be more easily deflected over them. To guard against side winds, folding triangular deflectors have been provided and there is a serrated rubber curtain along the lower edges of the deflectors, which is an additional aid in preventing wind from getting underneath the shield.”

According to the company’s test results 63 to 100 per cent of the spray drift could be prevented by the Nodrif boom. Furthermore, at a wind velocity above 12mph, 18 to 28 per cent of the spray was blown away when ordinary spray booms were used.

Pest Control’s solution also paid attention to protecting the workers applying toxic sprays. In 1950, a working party set up by the Ministry of Agriculture was invited to make recommendations for the promotion of the safety of workers using toxic substances in agriculture. By 1951 the group had put forward suggestions that included protective clothing and arrangements for decontamination.

Pest Control said additional protection was given by the use of a Nodrif boom ‘as it helps to ensure that operators are not smothered by the chemical when spraying operations in wind are carried out.’

“But the firm has also made improvements in the gasproof air-conditioned tractor cabs which it produces for its contracting plant,” said The Engineer. “The improved cab…is an almost air-tight cabin, into which air is passed through a compressor driven from the power take-off of the tractor. On the intake side of the compressor there is a large charcoal filter which absorbs gases and in front of it is a filter for collecting fine smoke and dusts.

“A pressure, rather higher than the atmospheric pressure, is maintained, and the air escapes through the gaps in the cab structure through which the tractor controls pass. A parasol-like sunscreen has been fitted over the cab so that a large part of the glass side-panels is shaded from the sun.”

The ministry’s working party stipulated also that spraying operations should cease if the temperature rose above 80^oF, a point heeded by Pest Control whose air-conditioned cabs were kept below 76^oF.

“This is effected by heat insulation and by trickling water over the cab - a method often used in greenhouses in tropical countries,” said The Engineer. “The spraying machine has to be frequently refilled with water and it is therefore a simple matter to refill the tank on the air-conditioned cab at the same time.

“As soon as the thermometer inside the cab registers a temperature above 70^oF, the operator turns on a tap, which sets the water-cooling device in action.”