14 



NATTTRAL CHECKS. 



The blackhead worms are little, if any at all, subject to parasitic 

 attack. The check for these seems to come in the mortality among 

 hibernating eggs. Only a small fraction of those that are on the plants 

 in midsummer survive to hatch during the following spring. But 

 while the blackheads are kept within certain bounds by these natural 

 conditions, they do very serious injury to the cranberry crop. 



The " yellowhead " (Teras) is much more subject to parasites, though 

 the first brood of worms is but little attacked. In the second brood 

 matters have changed, and out of a given number of worms collected 

 near maturity less than 50 per cent became adult. In the third brood 

 conditions are yet further modified and not over 25 per cent of the 

 worms develop to the adult stage, leaving, however, a goodly number 

 to go into the winter. During this season many others die off because 

 of adverse weather conditions, but still enough remain. 



In general, on any given infested area, both of these cranberry worms 

 will hold their own and even increase under natural conditions. The 

 grower has nothing to hope for from the ordinary checks provided by 

 nature. 



REMEDIAL. MEASURES. 



Flowing the bog. — The application of insecticides on large bog areas 

 where the plants cover the ground as densely as do the cranberry vines 

 is a task no grower likes to contemplate; and provided he has control of 

 a satisfactory amount of water there is no necessit}^ for it. As against 

 the "yellowhead" (Teras), it will suffice if the water be held on the 

 bogs until the middle of May, or perhaps a little later in cold seasons. 

 By this time the huckleberr}^ and heath plants have made a good 

 growth and have tempted the hibernating moths to lay their eggs. 

 Unless, therefore, the vines are uncovered at the edges or on knolls 

 above water, the plants will be free from the first brood of worms. 

 In the woods and on the upland plants the worms and even the moths 

 are exposed to the attacks of birds and many predatory insects that 

 never go upon the bogs; hence the adults of the first summer brood 

 will not be nearly as plentiful as if they had bred on the vines. 

 Only a few, comparatively, of the moths will fl}^ upon the bogs, and 

 even then do not usually get very far from the edges; so the heavy, 

 ver}^ injurious middle brood will be reduced to practically harmless 

 numbers. The third brood, even if it does spread over a greater area, 

 is not likely to prove troublesome, for reasons already stated. Hence, 

 care and attention to the drawing of the water in spring will of itself 

 suffice to keep this insect in check. If to this we add the destruction 

 of the heath and huckleberry plants immediately surrounding the 



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