42 MASS. EXPERIMENT STATION BULLETIN 441 



At comparable strengths, the DDT emulsions lasted longer than the DDT 

 wettable powder sprays; and as far as the test went, the DDD emulsions seemed 

 to give results somewhat below those obtained with the DDT wettable powders. 



In the early spring ot 1947, several commercial DDT emulsion concentrates 

 were applied while the trees were still dormant, at strengths up to 2.0 percent 

 DDT, and no noticeable injury to the elms was observed. The long-term residual 

 effects of these spray deposits are being studied, as is also the possibility of beetles 

 feeding on the new unsprayed twig growth which appears after the dormant 

 spray application. 



Future studies may reveal whether laboratory feeding tests such as these 

 approximate what might actually happen in the field where the beetles can move 

 about freely, and to what extent the occurrence of Dutch elm disease will be 

 affected by the reduction of this twig feeding. 



Use of a Mist Blower to Apply Concentrated Sprays to Elms to Prevent Twig 

 Feeding by the Smaller European Elm Bark Beetle. (W. B. Becker.*) A new 

 Buffalo turbine blower was used to apply DDT to large elm trees in the forms 

 of concentrated (up to 15 percent) oil solutions and water emulsions. The spray 

 nozzle was altered so two cone-shaped jets of spray were ejected into the high 

 velocity air current in the mouth of the blower. An output of as little as nine 

 gallons of spray per hour could be applied. 



Preliminary experiments with this mist blower resulted in relatively long last- 

 ing prevention of S. niuUistriatns twig feeding in the lower portions of an elm 

 (20 to 25 feet from the ground) when sufficient spray was directed at the tree. 

 However, in the upper portions of medium-sized elms (60 to 65 feet high) pro- 

 tection was often relatively short, even when one and two gallons of a 12 percent 

 spray were applied to one such elm. When dosages were near those used to 

 combat defoliating insects (approximately one quart of a 12 percent DDT spray), 

 long-term protection against 5. multistriatus twig feeding was often not satis- 

 factory even on the low branches 20 feet from the ground. Freshly cut twigs 

 from different heights in the elms were tested in gallon size jars as described under 

 the preceding title. 



Preliminary experiments with this mist blower point out that for reaching the 

 tops of shade trees best results are obtained when there is no wind movement. 

 Naturally, when using such strong insecticides, even in mist form, one must 

 avoid getting too close to the plants, and also avoid putting on an excess of the 

 spray mist; otherwise plant injury may result. 



Experiments are being continued with different types, strengths, and volumes 

 of spray. 



*The author is indebted to entomologists at the Field Headquarters, Gypsy and Browntail Moth 

 Control, of the United States Department of Agriculture, Bureau of Entomology and Plant Qtiar- 

 antine, at Greenfield, Mass., for much helpful information about mist blowers and their operation. 



FEED AND FERTILIZER CONTROL SERVICES 

 John W. Kuzmeski in Charge 



The feed, fertilizer and milk testing laws are administered as one service and 

 the operations of each, with the exception of the milk testing law, are reported 

 in annual bulletins. 



Under the milk testing law 11,089 pieces of Babcock glassware were calibrated 

 and 191 certificates of proficiency in testing were issued. All milk depots and 



