858 EXPERIMENTAL FARMS 



5 GEORGE v., A. 1915 

 NOVA SCOTIA. 



Mr. G. E. Sanders had charge of the scouting work in this province 

 during the winter of 1912-13. It was found that the infestation had spread in 

 an easterly direction, single winter webs being found at ShefRelds Mills, Kings county, 

 and Falmouth, Hants county. The number of new infestations, however, was less 

 than the previous season. There was an increase in the number of winter webs 

 collected, 11,054 webs being found in an area which included portions of the five 

 counties from Yarmouth to Hants. 



The distribution of the winter webs according to food plants in Nova Scotia was 

 as follows : — 



Apple 9,755 White Birch 9 



Pear 359 Beech 4 



Thorn • 338 Wild Cherrv 2 



Plum 327 Elder 1 



Wild Pear 122 Poplar 1 



Oak SO Prune 1 



Maple IG RasplDcrry . ..." 1 



Wild Rose 14 Alder • 1 



Elm 11 Quince 1 



Sweet Cherry 11 



Mr. Sanders continued his investigations on the bionomics of the Brown-tail 

 Moth under I^ova Scotia conditions. One of the most serious problems is the drop- 

 ping of the winter webs on to the ground, thus they escape collection. This " winter- 

 drop " is being carefully studied in all its aspects. Winter webs were placed on the 

 ground in different localities and left from December, 1912 to April, 1913. The 

 greatest winter-kill in any of the lots of 25 webs was 7-57 per cent, practically a 

 negligible quantity. Having demonstrated the ability of larva? in dropped nests to 

 survive the winter on the ground practically unharmed, experiments were carried out 

 with a view to ascertaining! whether such larvse could find food on the ground, and 

 whether or not they could successfully reach suitable trees. It was found that they 

 would thrive on the ordinary lierl^age such as clover, timothy, dandelion, wild straw- 

 berry, etc., for forty-four days, which was a sufficient length of time to enable them 

 to travel 300 feet or more on the ground and reach suitable trees. Altogether, 3,529 

 young caterpillars out of 5,365 used in the experiments, or 65-7 per cent., found the 

 trees under conditions which unusually occur in the field. 



This ability to survive in winter webs which drop to the ground before winter 

 explains many cases of re-infection that are otherwise inexplicable. Field observations 

 showed that the percentage of nests hanging by a single thread and readv to drop 

 would sometimes be as high as 20 per cent. The results of our scouting work from 

 year to year indicate that the successful control of the Brown-tail Moth is possible 

 by our present methods of thorough scouting were it not for the re-infestations which 

 take place by moths being carried over by the wind from the New England States, 

 and our present inability to deal with the problem of the dropped nests to which 

 we are giving our attention. 



It is satisfactory to find from our scouting work that the infestation of the Brown- 

 tail ]\roth in the orchards is leas't in those orchards v.'here spraying is regularly prac- 

 tised. The occurrence of unsprayed orf^hard", thorn thickets and wild apple, etc., in 

 various infested localities serves to supply a nermanent breedings place where artificial 

 control is difficult. 



Importatiox of Parasites of the Bhown-tail and Gipsy Moths. 



The ultimate control of the Brown-tail Moth must necessarily be a natural one, 

 and while we have, so far, successfully held the insect in check by thorough scouting 

 work and the collection of the winter web?, the natiiviil spread of the moth from the 



Ottawa. 



