Herbert Spencer

EXPERIMENTS IN 1952 FOR CONTROL OF THE CITRUS RED MITE

In 1952 experiments for control of the citrus red mite (Paratetranychus citri [McG.]) were continued in a grove of Temple orange trees at Fort Pierce, Fla. The trees were arranged in 10 blocks with 9 treatments randomized in single-tree plots in each block. The trees had been used in 1949 and 1950 (Spencer and Norman, 1951) and in 1951 (Norman and Spencer, 1952) for earlier experiments. On February 9, 1952, all trees were sprayed by the owner 2 with a mixture containing 2/3 pound of 40-percent dinitro-ocyclohexylphenol (DN Dry Mix No. 1), 3 pounds each of zinc carbonate and manganese oxide, 10 pounds of wettable sulfur, and 16 pounds of urea (Nugreen) per 100 gallons. The dinitro-ocyclohexylphenol was for the control of the citrus red mite. At postbloom spray time, March 31, a mixture containing 2 pounds of basic copper sulfate, 1 pound of 15-percent wettable parathion, and 10 pounds of wettable sulfur per 100 gallons was applied by the owner to all the trees. On May 28 a prespray estimate of infestations was made. One unhatched egg or crawling stage was enough to classify a leaf as being infested. On this basis citrus red mite infestations of 20 percent or less require no control. Infestations on leaves and fruits ranged from 76 to 88 percent, but the differences between treatments were not significant, an indication that the 1951 treatments had no influence on the present infestation, and that the dinitro compound applied in February controlled the red mites only until mid-May. The parathion used in the March postbloom spray, together with the basic copper sulfate, may have had a great deal to do with the reappearance of the red mites in heavy infestation during May. Apparently, winter applications of the dinitro compound cannot be depended upon to control red mites through the year on trees that receive copper, zinc, manganese, and/or parathion in winter or in postbloom applications. A summer miticide should be added to the sulfur rust mite spray in June or July for year-around control.

SAMPLING OF INFESTATIONS OF CITRUS RED MITE

Entomology Research Branch . The citrus red mite,1 known generally in Florida as the purple mite, has become a major pest of citrus, especially in the last ten years. Since 1913 the Subtropical Fruit Insects Laboratory at Orlando has conducted many experiments with insecticides and miticides for control of this pest, and also experiments designed to reveal the causes of infestation increases. Sampling methods have been devised to measure natural infestations and also the control obtained with the many treatments that were tested. Sampling for reliable experimental data is at best a timeconsuming and expensive work. Through the years several methods have been tried in a continuing effort to obtain more reliable data at less cost of time and labor, and to find a simple method that might be useful also to citrus growers in checking their own groves. Experiments involving comparisons of insecticides or miticides for control of red mites are conducted in a single grove of uniform trees to avoid variations between groves. A randomized-block design is used (Spencer and Osburn, 1948). Ten compact blocks of trees are outlined on a map of the grove, each block including a tree for each treatment. By this method all treatments are subjected equally to any variations that may exist between different parts of the grove. Our present method of estimating infestations has several advantages. We use a hand lens in the grove, and so avoid collection and transportation of samples to the laboratory and use of the microscope. We examine only top surfaces of the leaves, since that is where most of the red mite eggs and crawling stages are found. This is simpler than examining upper and lower leaf surfaces and fruits, and gives larger numbers and less variation for equal time spent. The hand lens we use is a linen tester with frame having an opening, or field, one inch square. The opening is placed diagonally over the midrib on the upper surface of the leaf, and records are made of the numbers of crawling mites and unhatched viable eggs in the square. This is done for 25 leaves equally

Parathion for Control of Purple Scales on Early Varieties of Oranges

Control of the purple scale, Lepidos;aphes beckii (Newm.) on early varieties of oranges has been a troublesome problem for citrus growers. Infestations often develop in the fall, and oilemulsion sprays applied for control after mid-July retard coloring of the fruit and delay internal maturity. Many Hamlin oranges so sprayed do not reach maturity standards that permit shipment to the market. In 1947 and 1948 experiments (Spencer et al, 1952) on Valencia (late) oranges showed that purple scales could be controlled as well with parathion as with oil-emulsion sprays. Further, the fruit sprayed in the fall with parathion colored and matured normally, and was of much better quality than that sprayed with oil emulsion. This work suggested the possibility of using parathion to control scales late in the year on early varieties. EXPERIMENTS IN 1949-50 Accordingly, in 1949 six cooperative experiments 2 were set up to compare oil emulsion with parathion for control of scales on early oranges, and to study the effects of these insecticides on coloring, maturity, and internal quality of the fruit. There were five groves of Hamlin oranges and one of Parson Browns (grove 5). In each grove there was a block of 70 trees (7 rows of 10 trees each), where 7 spray programs were compared over a 2-year period, each program being applied to 10 trees. The spray programs are shown in table 1. The oil emulsion, a 90 percent cream-type concentrate, was added to water in the spray tank to give a spray containing 1.25 percent of oil. Two pounds of 15 percent wettable parathion per 100 gallons of water was used with 5 pounds of wettable sulfur added for controlling the citrus rust mite, Phyllocoptruta oleivora (Ashm.). Power sprayers of 500-gallon capacity were

Insecticidal Control for the Sugarcane Borer

The work of three seasons at the Louisiana Experiment Station has yielded consistent results showing that it is possible with a water-soluble dust like sodium silicofluoride to destroy at least half of the sugarcane borer larvae occurring on the exterior or burrowing through the interior of the stalks of corn or sugarcane which are the principal host plants of this species in Louisiana. With many of the more than fifty (50) materials tested thus far there has been a degree of burning of foliage of corn which is serious, but on cane which is much more resistant to chemical burn, a number of materials have been found safe and effective enough to justify extensive field applications which may at least supplement other measures in controlling this pest.