THE MONTHLY BULLETIN. 557 



THE USE OF FLOUR PASTE IN LIME-SULPHUR SOLUTIONS 

 IN THE CONTROL OF THE CITRUS RED SPIDER. 



By J. D. Neuls^ Expert, U. S. Dept. of Agriculture, El Centre, Cal. 



At the writer's suggestion, a few tests, using commercial lime-sulphur 

 Math the addition of flour paste made according to the directions in 

 Circular No. 166 of the Bureau of Entomology by Mr. W. B. Parker, 

 were made by Mr. Sweigert, the inspector at Whittier, against the 

 citrus red spider {Tetranychus mytilaspidis). In all the plots treated, 

 a few trees were sprayed with lime-sulphur solution without the flour 

 paste added, as a check. Although the experiments were few and 

 owing to the departure of the writer to other fields, were not carried 

 through to the desired completion, the results were so satisfactory 

 that the writer was requested by Mr. Essig to publish a brief account 

 of the results. 



No difficulty was encountered in picking out the trees that were 

 sprayed Avitli the lime-sulphur alone. The spotting of the leaves and 

 fruit, familiar to all who have had occasion to use the lime-sulphur 

 solution, was not to be found on the trees where the flour paste had 

 been added. So even was the distribution that only by a close examina- 

 tion could one tell that the tree had been treated. Conversation with 

 the sprayer brought out the fact that hereafter, even if the grower 

 refused to sanction the small additional expense of the flour paste, 

 the sprayer would add it himself because the pumps worked much 

 better. There was no clogging either in the pumps or at the nozzle 

 and a two hundred gallon tank of the spray with the flour paste added 

 would cover more trees than with the lime-sulphur alone. 



The chief objection to the lime-sulphur solution has been that it 

 spotted the fruit, particularly oranges, necessitating washing. These 

 experiments point to the fact that with the additional flour paste the 

 washing of the fruit may not be necessary. The distribution of the 

 lime-sulphur is so even when the flour paste is added that it spreads 

 over the surface of the leaves and fruit in a thin film so that very little 

 spotting occurs. The few spots that do occur and which are generally 

 formed where the solution drops off the leaves or fruit, are of such a 

 character (because of the flour paste) that they dry and crack, so 

 that if they do not fall off of their own accord in the field they are 

 very easily brushed or rubbed off in picking. It was the intention of 

 the writer to follow up the fruit that had been sprayed with the lime- 

 sulphur and flour paste to the packing-house to see whether or not it 

 had to be washed, but circumstances prevented. 



The effectiveness of the commercial lime-sulphur solution with the 

 flour paste added in the right proportion is increased owing solely to 

 the fact that the distribution is much greater. The insecticidal value 

 of the lime-sulphur solution against red spiders is the best known of 

 any remedy and the addition of the flour paste seems to bring this 

 solution to the highest point of efficiency. 



.The purpose of this article is to bring these points and suggestions 

 before the minds of those interested in the control of the citrus red 

 spider with the hope that it may stimulate others to experiment along 

 this line and thus develop a thorough and efficient method in con- 

 trolling this serious pest. 



