46 MASS. EXPERIMENT STATION BULLETIN 249 



Stickers. The addition of stickers or spreaders to the poison has consistent- 

 ly reduced the number of days necessary to kill the beetles as well as the 

 number of punctures made in sprayed fruit. 



Light p)-essed Menhaden Fish Oil (6) proved to be the most effective 

 sticker and its use seems practical. In laboratory experiments the number of 

 punctures in the fruit was generally decreased from one-third to one-half 

 by its use, and the beetles died more quickly than when feeding on lead 

 arsenate alone. In orchard experiments in 1927, the lead arsenate — fish oil com- 

 bination gave 15.52 per cent better control than the lead arsenate — calcium 

 caseinate formula. It is recommended that 4 liquid ounces of fish oil be used 

 for each pound of powdered lead arsenate regardless of the amount of spray 

 solution, but more than 1 pint (16 ounces) is unnecessary in 100 gallons of 

 any spray formula used on orchard trees. The fish oil should always be 

 added after the poison has been thoroughly agitated in the solution for 

 several minutes, and the agitation continued until ' the two materials are 

 thoroughly mixed. This rapidly drying oil is available in most cities and 

 can be purchased in Boston for about 80 cents a gallon, the price varying 

 with the quantity. Raw linseed oil may be satisfactorily substituted but 

 is more expensive. 



A cheap grade of molasses, such as is used for feeding cattle, when added 

 to the spray at the rate of 1 gallon in 100 gallons, increased the effectiveness 

 of the poison by 16.58 per cent in an orchard heavily infested by the plum 

 curculio in 1927, and also made the poison more effective in several labora- 

 tory experiments. The cost is usually greater than that of fish oil, and it 

 is less desirable. 



Cnldnm Caseinate. manufactured under several commercial names, is gener- 

 ally used in all sprays in which lead arsenate and lime-sulfur solution are 

 combined, to reduce undesirable chemical action between these materials. 

 Many experiments throughout the country have failed to show conclusively 

 that it increased the effectiveness of lead arsenate, yet in several laboratory 

 tests on this project it had a slight value. It is used at the rate of 1 pound in 

 each 100 gallons of spray, and when mixed with lead arsenate and lime-sulfur 

 solution should be added to the spray between the active materials. 



A comparison of the value of the various stickers with lead arsenate, under 

 laboratory conditions, for combating the plum curculio is given in Table 14. 



Combination Sprays. Since it is necessary to secure protection from apple 

 scab and other fungous diseases as well as from insect pests, fungicides are 

 combined with the poisons wherever possible. Orchard spraying experiments 

 in 1926 indicated that the lead arsenate-calcium caseinate-lime-sulfur solu- 

 tion formula was not as effective against the plum curculio as when the 

 lime-surfur solution was omitted. Later observations failed to confirm this 

 belief, and any difference in the efficacy of these combinations is not con- 

 sidered significant as is shown in Table 15. Under normal conditions, however, 

 it is believed that the fungicide can be safely omitted from the 7-day spray, 

 at least on varieties other than Mcintosh. 



Orchard Spraj/ing Experiments. 



In conjunction with the laboratory experiments, spraying experiments 

 were conducted in a four-acre orchard at North Littleton, which was isolated 

 from other bearing apple trees. The varieties in this orchard are Mcintosh, 

 Baldwin, and Wealthy, and the count trees included some of each. The 

 control of the plum curcuHo in this orchard by spraying was very good in 

 spite of a heavy infestation, yet indoubtedly the percentage of blemished 



