ANNUAL REPORT, 1936 47 



aphid was a problem, and satisfactory results were reported. For the most part, 

 however, growers continued to apply the conventional types of oil sprays and 

 confined themselves to old and well-established brands. 



Outstanding among the new types was Ready Mix Kleenup manufactured 

 by the California Spray Chemical Company, a light-bodied product of the 

 miscible type, very stable, with a high percentage of active oil. It consisted of 

 95 percent petroleum oil, 4 percent cresol compounds and but 1 percent inert 

 ingredients (chiefly water). This product required a special method of prepa- 

 ration for spraying and more time for final dilution than does the usual type 

 of oil sprays. In the course of mixing, whether the material was simply run 

 through the pump or whether the spray nozzles were opened and turned back 

 into the tank, considerable froth was developed. This was believed to be due 

 to hard or chlorinated water. (The manufacturer furnishes a "conditioner" 

 to remedy this.) It was noted that when this froth was allowed to stand, a 

 considerable amount of free oil quickly separated out. This separation would 

 make it difficult to determine the strength of the oil in the spray applied and 

 might also be a source of danger to the trees. The material, however, proved 

 very effective against overwintering eggs of the European red mite and com- 

 pared very favorably with the standard type of Kleenup, as shown in the 

 following table. 



Number of Percentage Average 



Dosage per mites per 100 of clusters number of Percentage 



Treatment 100 gals. leaf clusters free from mites per of control 



mites leaf 



Ready Mix Kleenup 3 y 2 gals. 76 85 0.13 98 



Flowable Kleenup 4 gals. 189 83 0.3 95 



Check — 3,786 6 6.3 



Spray Materials for the Control of Gladiolus Thrips. The experiments con- 

 ducted in 1936 were of two types. 



1. Comparison of effectiveness of derris and a thiocyanate in control of the 

 gladiolus thrips. In these experiments Derrisol, Ku-ba-tox and Lethane 420 

 were used as spray materials at dilutions of 1-600. Four applications were 

 made at weekly intervals when the infestation began to develop, and the 

 comparative effectiveness was determined by the amount of injury to the 

 plants and blossoms. The derris sprays were superior to the thiocyanate 

 compound. These tests again demonstrated that if spraying is delayed until 

 a heavy infestation has developed, and particularly after the flower spikes have 

 appeared, no spray can be depended upon to give satisfactory control. 



2. Comparison of the effect of certain contact sprays and stomach poisons 

 upon corm production. In 1935 observations on corms of mixed varieties in- 

 dicated that in the absence of a heavy thrips infestation certain stomach poisons 

 reduced the average weight per corm of the corms produced. In 1936 experi- 

 ments in which various insecticides were applied to plots of the same variety 

 substantiated this belief. All stomach poisons reduced the average weight per 

 corm below that of the unsprayed checks. 



Substitutes for Lime-Sulfur in Summer Sprays for Orchards. Tests of these 

 materials were continued in cooperation with the Department of Pomology. A 

 period of unseasonably high temperature in late March which caused fruit 

 buds to unfold much earlier than usual was followed by cold weather and 

 frequent rains during April that slowed down further development. As a 

 result, new growth was exposed to scab infection for a long period. The test 

 blocks in the college orchard were given an emergency pre-pre-pink application 



