38 MASS. EXPERIMENT STATION BULLETIN 398 



mercial neutral copper fungicide, the plants were badly riddled by flea beetle, 

 began to die down in late July, and a large proportion were dead by late August. 

 The yields in all the bordeaux-treated plots were very satisfactory. 



The results in the plots treated with 23^-2 J^-50 bordeaux were very satisfactory 

 and encourage the hope that, during the present emergency at least, reasonable 

 protection from disease and insect pests may be secured with a considerable 

 saving in materials. 



Investigations on the Effect of Insecticides on Honeybees. (A. I. Bourne and 

 F. R. Shaw). The investigations during 1942 were conducted along two main 

 lines: 



L The use of materials that might be added to spray or dust mixtures to 

 repel bees. Of those used, creosote appeared to be the most effect've m repelling 

 the bees but Injured apple foliage. Tests are being continued to try to find some 

 material that will be effective as a repellent and yet be safe on plant foliage. 



2. The effect on bees of materials used as ant poisons, together with an in- 

 vestigation of the danger of bee poisoning resulting from the use of commercial 

 ant baits. The ant poisons tested contained either thallium sulfate or some 

 arsenical, most commonly sodium arsenite. Because the arsenical compounds 

 killed the bees so quickly, there was less danger of the poison being carried back 

 to the hive than in the case of the slower acting thallium compounds. 



Experiments with commercial ant traps, used as directed by the manufacturer, 

 indicate that very slight danger to bees will result if the ant poisons are in salve 

 boxes or similar types of containers. The use of sweetened ant baits exposed 

 openly would appear questionable, not only from the danger to bees but also 

 from the aspect of safety to man and other animals. 



Naphthalene and Similar Compounds as Greenhouse Fumigants. (W. D. 



Whitcomb and \Vm. Garland, Waltham.) Experimental fumigations using a 

 mixture of monochlor naphthalene 3 parts and flake naphthalene 1 part were con- 

 tinued at various relative humidities. Satisfactory control of the common red 

 spider mite occurred only after ^ ounce of the fumigant was vaporized in 1,000 

 cubic feet and the mites had been exposed for 3 hours. Fumigations at 50, 60, 

 70, and 80 percent relative humidity and 60°F. showed no significant differences 

 as the relative humidity was increased, indicating that this factor Is less important 

 than temperature, which has shown increased mortality at the higher tempera- 

 tures. 



Biology and Control of the Apple Leaf Curling Midge. (W. D. Whitcomb, 

 Waltham.) In emergence cages in the insectary no midge flies emerged in 1942 

 from maggots collected in June and July 1941, while 67 percent of the maggots 

 collected In August transformed to flies in 1942. 



Emergence of the first generation flies at Waltham was about two weeks later 

 than in 1941 and oviposltlon was negligible on the trees under observation. 

 Emergence of flies again occurred July 20-25 and August 8-15, and the greatest 

 oviposition of the season occurred August 18-27. Larvae were collected In bands 

 in large numbers on July 28 and on September 10, and precipitation exceeding 1 

 inch was recorded at each time. The influence of rain in causing the maggots 

 to leave the rolled leaves was very noticeable. 



Treatment of the soil under lightly infested trees with naphthalene flakes at 

 the rate of 2 pounds per 100 square feet gave almost complete control of midge 

 flies for both the first and the second generations. Spraying during the height 

 of the oviposition period of the second generation, caused a measurable reduction 

 in the number of infested tips where a rotenone or a DN spray was used but no 

 reduction where a pyrethrum spray was used. 



