ANNUAL REPORT, 1933 29 



The effectiveness of this material compared very favorably with that of mag- 

 nesium arsenate, the standard treatment; furthermore, reinfestation was very 

 slow following the application of Dutox. Manganar, a manganese arsenate, 

 diluted with hydrated lime at the rate of 1 part to 4 and applied as a dust, caused 

 very severe burn. Nicotine sulfate (1-800) and Red Arrow, a pyrethrum com- 

 pound, (1-400) proved effective as contact sprays. They reduced the numbers 

 of bean beetle larvae but reinfestation was rapid, and consequently with such 

 sprays frequent applications are necessary. Tests with pyrethrum dust and a 

 rotenone dust showed these materials to have an excellent initial effect upon 

 bean beetle larvae but neither of them appeared to have the residual effect of the 

 fluosilicate compound mentioned above nor did they furnish protection over as 

 long a period as the standard treatment with magnesium arsenate. 



In most of the plantings of gladiolus, where the corms had been given the dor- 

 mant treatment with either hydrocyanic acid gas or naphthalene, the gladiolus 

 thrips did not develop to serious numbers until comparatively late in the season; 

 and in many fields well isolated from other plantings, thrips were relatively 

 scarce throughout the season and caused practically no damage — another dem- 

 onstration of the effectiveness of these dormant treatments. Collections during 

 this season showed that undoubtedly more than one species of thrips attack 

 gladiolus. This explains why, in some fields where the corms were treated during 

 the dormant period and consequently were free from thrips when planted, a 

 serious infestation developed during the early season. This strengthens the rec- 

 ommendation that all crop remnants, chaff, etc., be destroyed after the bulbs 

 are pulled in the fall and that, so far as possible, weeds and grass on the margin 

 of plantings be burned over to kill thrips hibernating there. Of the spray mate- 

 rials and combinations tested, the Paris green-molasses spray showed to best 

 advantage based on the appearance of the florets as well as on the effect upon 

 thrips. A pyrethrum dust also gave good results. Derrisol (1-600), p\Tethrum 

 spray (1-600), and a combination of nicotine sulfate (1-800) and Penetrol (J^ of 1 

 per cent) proved to be about equal in value but were slightly less effective than 

 the Paris green-molasses spray. Dusting sulfur proved to be unsatisfactory. 



The studies of various substitutes for lime-sulfur, carried on in cooperation 

 with the Pomology Department, were confined chiefly to those materials which 

 had proved outstanding in previous tests, with the addition of two new materials 

 recently developed which appeared to be especially promising. All of these 

 were used in combination with lead arsenate, and the complete schedule of seven 

 sprays was followed. The efficiency of each material was measured in com- 

 parison with the standard lead arsenate and lime-sulfur combination. 



The wettable sulfurs were applied in the sprays after the special curculio fol- 

 lowing the use of lime-sulfur as a fungicide up to and including the calyx. In 

 all cases the special curculio application comprised lead arsenate and fish oil 

 without any fungicide. 



Further studies were made on the effectiveness of Kolofog and of flotation 

 sulfur when used throughout the season as compared with the results secured 

 when these materials were used following lime-sulfur in the pre-blossom sprays. 



A combination of magnetic sulfur and lime-sulfur with lead arsenate was also 

 applied in a complete schedule. It was hoped such a combination would give 

 effective control against scab, avoid the burning that usually follows lime-sulfur 

 in summer applications, and at the same time provide a spray more economical 

 than the commercial brands of wettable sulfurs. 



The lime-sulfur-lead arsenate combination again caused more or less burn 



