311 



increase the degree of iniury. Sudden changes of temperature over 

 a wide range during exposure to the gas tend to increase plant injury 

 considerably. The optimum environment for safety to plants is 

 diffused light or darkness at uniform temperatures below 80° F. before, 

 during, and after fumigation ; the lowest temperature tried, 55° F., 

 was within the optimum range. Fumigation at temperatures upward 

 of 80° F. is safest under cool pre- and post-fumigation environments. 

 The maximum of injury follows high temperatures for all three 

 environments. 



The phvsical and chemical conditions of the soil influence injury 

 from fumigation. Trees in a wet soil tend to suffer more than healthy 

 trees in a drv soil. Trees weakened by drought are, however, more 

 susceptible to injury than if grown under optimum moisture conditions. 

 Irrigation should follow fumigation, not precede it. 



The physiological condition of the plants is a most important factor, 

 and a condition of hardiness is the optimum for gas resistance ; 

 it is brought about by dryness of soil, cold weather, and possibly by 

 continued verv hot drv weather. 



IxGERsoN (H. G.). Life-history of the Grape-herry Moth in Northern 



Ohio.— U'.S. Dept. Agric, Washington, D.C., Buh. 911, 13th 

 December 1920, 38 pp., 5 figs. [Received 20th April 1921.] 



In northern Ohio there is one full brood of Polychrosis viteana, 

 Clem., and a partial second in the year, the second brood of cater- 

 pillars being much larger and more destructive. P. viteana hibernates 

 in the pupal stage in cocoons in old grape leaves under the grape trellis. 

 The mortality of such pupae was from 76 to 80 per cent. The first 

 moths emerge in spring about 10 days before the grapes begin to bloom, 

 but the greatest emergence was during and immediately after 

 the bloom. Oviposition begins about four days after emergence ; 

 incubation takes 3-10 days, with an average of 5 days. 



The first brood larvae feed in the j^oung grapes for 14-37 days 

 — with an average of 20-6 days in 1917. They then spin their 

 cocoons on the tender leaves. The prepupal stage lasted 1-3 days 

 in 1917, and the pupal 11-16. The hfe-cycle of the first generation, 

 taken as a total of the separate stages, was 39-79 days, with a 

 maximum total of 76 and a minimum of 23. 



The second brood egg-stage varied from 4 to 10 days. The feeding 

 period was from 16 to 36 days in 1916, with an average of 24-18, 

 but all other records have given 40 days, which is probably more 

 accurate. Second-brood caterpillars begin to leave the fruit early 

 in the autumn. In each brood the females predominate, there being 

 three or more females to one male. A small part of the first brood 

 caterpillars hibernate and yield moths in the following spring. Notes 

 are given on mating and oviposition. The habit of the caterpillars 

 of feeding on the leaf-galls of the grape-vine Phylloxera was observed. 

 The caterpillars can resist extremely low temperatures, such as 17° F. 

 Parasitism was very low and of no value as a check. The measures 

 advised are cultural methods that will expose the hibernating pupae 

 to the elements. Satisfactory results were obtained by two appli- 

 cations of spray by the " trailer " or hand method of spraying. The 

 first application should be made 3-5 daj's after the young grapes set, 

 and the second when the grapes first touch in clusters. 



