The principal parts of the duster consist of the chamber for holding the dust, the air pump for supplying the air blast, and the delivery tube and nozzle. The dust chamber may be of glass or metal construction. The nozzles on some dusters may be adjusted at various angles to obtain better under-leaf coverage. These dusters sell for 50 cents to 2 or 3 dollars.

Crank and knapsack dusters are designed for use on estates, in large gardens or small acreages of truck crops, and on field crops such as cotton or tobacco. They are also useful for controlling spot infestations in larger fields before making a general treatment with large equipment.

The crank and knapsack dusters are provided with dust hoppers holding from 5 to 25 pounds of dust, an agitator to prevent the dust from packing, and a mechanism to feed the dust uniformly into the outlet. An extension tube may be fitted to this outlet for dusting small fruit trees.

The crank duster is suspended in front of the operator by means of shoulder straps. An air blast is generated by a manually operated rotary fan or blower, which provides a continuous discharge of dust. To treat row crops, the dust may be put out through one or more tubes arranged to cover either one or two rows in front of or behind the operator.

The knapsack duster develops an air blast by means of a bellows rather than by a fan or blower. The dust is therefore discharged intermittently and for this reason the knapsack duster is particularly adapted for treating crops planted in hills or for spot dusting of crops in which the plants are widely spaced in the row. By continuous operation, however, this duster may be used for applying dust to other crops.

Wheelbarrow or traction dusters are intermediate between hand and power equipment. They are used for continuous dusting of small acreages of row crops. Because of their light weight and mobility, they may often supplement power dusters when fields are soft or rough.

These dusters are like the crank dusters but are of heavier construction and are mounted on wheelbarrow frames. Power is derived from the traction wheel of the unit; the fan is driven by a chain or belt. Wheelbarrow dusters are usually designed for two-row coverage and use two discharge nozzles per row. The nozzles are adjustable for crops of different height or for applying dust to the under sides of the leaves. The hoppers hold 15 to 50 Pounds of dust and the discharge rate may be varied from about 5 to 45 Pounds per acre. A clutch is provided for intermittent use in the field. Some larger models have a front hitch for Use in attaching to horse, mule, or garden tractor when larger fields are to be dusted. Crank and knapsack dusters range in price from 20 to 50 dollars and wheelbarrow dusters from about 75 to 125 dollars.

Household sprayers require little maintenance because of their simple design. They should be stored in a dry place. If the pump should lose its compression, a little lubricant should be applied in the air hole at the end of the cylinder to soften the pump leather and keep the seal with the cylinder wall.

Before the beginning of the spraying season, the general utility sprayer should be disassembled and inspected to make sure that it is in good shape. Worn parts, which may interfere with the operation of the unit, should be replaced. Repair or replacement parts can be bought from the local retail dealer or from the manufacturer. The sprayers should be cleaned after each use. After safe disposal of any insecticides remaining in the sprayer, the tank should be rinsed with clean water. Then the nozzle should be disassembled and cleaned and some clean water should be forced from the tank through the discharge line to remove any foreign deposits. The tank should then be dried or inverted for drainage and the whole unit stored in a dry place.

Before dusters are placed in seasonal storage, the dust reservoir should be emptied and thoroughly cleaned. Extension tubes should also be disassembled and all the joints cleaned of any dust deposits. Working parts on the larger dusters should be cared for in the manner prescribed by the manufacturer.

T. E. BRONSON, an entomologist, was associated with the Bureau of Entomology and Plant Quarantine from 1924 until 1951, when he resigned to join n a chemical company. He is a graduate of the University of Wisconsin.

EARL D. ANDERSON is secretary of the National Sprayer and Duster Association. He has degrees in agricultural engineering from Iowa State College.

Strawberry leaf beetle.