Precipitation Deficiency Research Articles

Weather, a Factor in Outbreaks of the Hickory Bark Beetle

The contents of this paper indicates that weather has a marked effect on barkbeetle outbreaks. A hickory barkbeetle, Eccoptogaster quadrispinosus , outbreak occurred during the drought period of 1925 in North Carolina. The marked deficiency in precipitation weakened hickory trees by checking growth and rendered them attractive to beetle attacks, favoring brood development. An excess of precipitation during periods of beetle flight resulted in a partial mortality of the adults, thereby considerably reducing the number attacking and also rendered trees unfavorable for brood development.

The Squash Beetle in Arizona, Occurrence and Probable Manner of Introduction

During 1921 the squash beetle ( Epilachna borealis Fab.) appeared in the vicinity of Douglas, Ariz. It slowly extended its range during the period 1921 to 1924 until it covered about 65 square miles. During 1925 the insect was not found within the previously infested area, and it is believed that a deficiency in precipitation, combined with an increase in the mean temperature, may have been responsible for the disappearance of the pest. The beetle differs from the Eastern form in being somewhat smaller in size and in the absence of marking on the prothorax. The dots on the elytra are also smaller.

Three Years of Paradichlorobenzene Experiments in the South

Paradichlorobenzene treatment of peach trees for control of the peach borer, Aegeria exitiosa Say, has become an annual practice in the program of orchard management in Georgia. Five hundred thousand pounds of the material were used in the Southeast during the 1923 season. The results of experiments indicate that under normal conditions the large doses exposed for short periods are not as effective as the smaller doses exposed for four to six weeks. No tree injury resulted from the use of the various doses around three, four and five year old peach trees in Georgia during 1921 and 1922 when normal weather conditions prevailed. However, during the 1923 season a precipitation deficiency occurred accompanied by abnormally high temperatures. These unusual weather conditions caused rapid action from the gas, and as a result some rather severe injury has shown up on three year old trees from the use of the ¾ and one ounce dose. During each of the three years no injury has resulted from the use of the ¾ ounce dose around four and five year old trees for twenty eight days. One and two year old trees have shown, each year, more or less injury from the use of the ½ and ¾ ounce dose. To date no injury has been revealed from allowing the mounds to remain around the trees over winter. Late October and November applications of paradichlorobenzene gave a control of around seventy-five per cent. December applications were worthless. Applications made around April 1st in Georgia gave about seventy pet cent control. Laboratory experiments show that the gas is liberated at about the same rate in both sandy loam and clay soils. Tests in the laboratory have repeatedly shown that the higher the moisture content of the soil and the lower the temperature, the slower is the action of the gason the borer.