Fumigation of greenhouses. — No general formula can be given for fumigating the different kinds of plants grown in greenhouses, as the species and varieties differ greatly in their ability to withstand the effects of the gas. Ferns and roses are very susceptible to injury, and fumigation, if attempted at all, should be performed with great caution. Fumigation will not kill insect eggs, and thus must be repeated when the new brood appears. Fumigate only on dark nights when there is no wind. Have the house as dry as possible, and the temperature as near 60° as practicable.

Fumigation of dormant nursery stock. — Dormant nursery stock may be fumigated in a tight box or fumigating house made especially for the purpose. Fumigating houses are built of two thicknesses of matched boards with building paper between, and are provided with a tight-fitting door and ventilators. The stock should be reasonably dry to avoid injury, and should be piled loosely in the house to permit a free circulation of the gas. Use one ounce of potassium cyanide for each 100 cubic feet of space, and let the fumigation continue forty minutes to one hour.

Fumigation of citrus trees. — In this case the tree is covered with an octagonal sheet tent made of 61/2 ounce special drill or 8 ounce special army duck, and the gas is generated in the ordinary way beneath it. The tent is so marked that when in position it is an easy matter to determine the distance over the tent and the circumference at the ground. When these figures are known, the

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Dosage chart for fumigating citrus trees (Bureau of Entomology, U. S. Dept. Agric.) proper dosage may be obtained from the above chart, which has been prepared for a strength of one ounce of cyanide for each 100 cubic feet of space.

The top line of numbers, beginning at 16 and continuing to 78, represents the distance in feet around the bottom of the tent. The outer vertical columns of larger numbers running from 10 to 59 represent the distance in feet over the top of the tent. The number of ounces of cyanide to use for a tree of known dimensions is found in that square where the vertical column headed by the distance around the tree intersects the horizontal line of figures corresponding to the distance over. Using fungous diseases as insecticides. — Fungous diseases have been successfully employed against the citrus white-fly in Florida. There are seven species of fungus which attack the white-fly, and nearly all are more or less valuable. The object is to introduce some form of the fungus into orchards and on trees where it is absent. This may be accomplished by spraying the under side of the leaves with a mixture of fungus spores in water. The mixture may be made by placing two or three fungus-bearing leaves in a quart of water, and stirring occasionally for fifteen minutes. Strain through cheesecloth, and apply to those parts of the tree most badly infested with the white-fly larvae.

The fungus may be introduced by pinning a dozen or so fungus-bearing leaves to the under side of the leaves of the tree infested with white-fly. The fungus-covered surface should face downward.