RED SPIDER AND POAVDERY MILDEW 287 



Linseed oil emulsion, developed by VinaP, combined a toxic action with the 

 ability to stick the spiders to the leaf when it dried. This spray has been used 

 quite effectively to kill the active and transforming stages of this pest but it 

 has little or no effect on the eggs, and frequently injures cucumber vines. 



Hi(/hly Refined White Mineral Oil Emulsion 



The most effective and satisfactory spraying material for the control of 

 red spider on greenhouse cucumbers is a highly refined white mineral oil 

 emulsion which contains no carbolic or cresylic compounds to aid in emulsi- 

 fication. Experiments with a spray of this type have consistently shown that 

 95 to 100 per cent of the spiders were killed by one application and that a 

 large percentage of the eggs which were thoroughly wet failed to develop. 

 Two thorough applications gave complete control. It was also observed that 

 many newly-hatched spiders were killed by crawling through the oily spray 

 residue several days after the applications. Many cucumber growers have 

 used this emulsion successfully during the past year in eastern Massachusetts. 



This highly refined wiiiLe mineral oil enudsion is a white, shiny, salve-like 

 material. It should be thinned with a little water before pouring into the 

 sprayer. For spraying cucumbers, a one per- cent dilution made by adding 1 

 gallon of the emulsion to 99 gallons of water, or IJ liquid ounces to I gallon, 

 should be used. At this strength it does not injure healthy cucumber vines 

 except when applied during temperatures of 95 °F., or higher, when burning 

 or a gradual hardening, and yellowing of the older leaves may result. Leaves 

 badly injured by red spiders or other pests may develop this condition more 

 quickly following the use of the emulsion, but this injury is much less than 

 if the pests were not controlled. Cucumber vines have maintained normal 

 growth and fruit production after ten applications of this spray at about 

 weekly intervals without evidence of injury. During the summer the spray 

 should be applied in the e\ening or during cloudy weather in order that it 

 may dry before being subjected to bright sun and high temperatures. In the 

 cooler seasons it can be used with safety at any time. If cucumber vines 

 are sprayed twice before they are 7 to 8 feet high, little injury by the red 

 spider will follow. In case later sprayings are necessary two applications 

 about one week apart should be sufficient. If small isolated infestations are 

 discovered before the mites have spread, two thorough sprayings of the in- 

 fested and surrounding area should eradicate the pest and protect the re- 

 mainder of the vines. Although this spray will control red spider on any 

 plants, its use on other greenhouse plants is advisable only when trials have 

 demonstrated that the plants are not injured. A white mineral oil emulsion 

 can be prepared at home for immediate use but it is recommended that the 

 commercial product now available on the market be used. This product is 

 uniform in quality and the diluted spray costs from H to 3 cents per gallon 

 depending on the quantity purchased. 



The spray Is best applied as a fine mist which thoroughly wets the vines, 

 especially the under side of the leaves. Knapsack, wheelbarrow, and com- 

 pressed air sprayers can be used for small areas and young plants, but in 

 spraying a large greenhouse, a power sprayer is desirable. The spray nozzles 

 should be set at an angle of about 60 degrees to the rod. 



^. Loc. dt. 



