10 UNIV. OF N. H. AGR. EXPERIMENT STATION [Bulletin 250 



vicinity of the new growth and tender buds before moving down the leader 

 to feed and oviposit. They are found on the leader until the middle of 

 July, at which time they either die or go to other parts of the tree. The 

 eggs, inserted in the cambium, hatch in from 6 to 20 days. The larvae 

 work their way down the leader, feeding on the inner bark and cambium. 

 After they have fed for three or four weeks each one enters the wood and 

 constructs a pupal cell where it remains for a varying length of time before 

 pupating. The larval stage occupies about 36 days. The pupal stage 

 lasts about two weeks and is followed by the eclosion of the adult. The 

 adults remain within the leader for two or more weeks. After emerging 

 the adults are found feeding on the branches of the white pine in increas- 

 ing numbers from the middle of September until the middle of October. 

 On the advent of cold weather they hibernate in the duff. Some adults 

 do not die after completing egg-laying but remain alive until a second sea- 

 son when they again lay eggs. 



No methods of complete control were developed, although several satis- 

 factory measures for materially reducing infestation in ornamental or 

 commercial plantations were found applicable. 



In small plantations the removal of infested leaders just below the 

 farthest point reached by the larvae, a common method of control, must 

 be practiced successively for several years in order to be effective. A 

 marked decrease in the number of weevils may not be noticed until the 

 third year. 



Silvicultural control may be brought about (1) by planting white pine 

 in mixed stands with hardwoods or other species of conifers; (2) by 

 planting white pine densely. 



In planting white pine in mixed stands the principle involved is to shade 

 the trees sufficiently to reduce weevil attack and at the same time not 

 interfere with the growth of the white pine. The fact that the weevil is a 

 sun-loving insect makes some measure of control by this method possible. 

 The hardwoods or conifers used in the mixture should slightly overtop the 

 white pine during the most susceptible period to weevil attack, that is, 

 until the trees are about 20 feet high. If this practice is followed care 

 must be taken not to let the shade trees overtop the white pine to such an 

 extent that growth of the latter is retarded and the trees become dwarfed 

 and weakened from competition. 



Many predators and parasites were found which keep the weevils rea- 

 sonably well under control. Lonchoea corticis, a dipteron predator, is the 

 most important natural control factor in New Hampshire. {Purnell 

 Fund.) 



KAINIT KILLS MUSTARD IN OATS 



Possibilities that mustard, a serious weed in oat fields in New Hamp- 

 shire, may be controlled by broadcasting finely ground kainit are indi- 

 cated by experiments conducted by O. Butler and Russell Bissey. Cyana- 

 mide proved even more effective, but its nitrogenous quality tends to 

 cause the oats to lodge. Both kainit and cyanamide must be applied 

 when the fields are wet. 



Several liquid sprays have also been found effective. When chemicals 

 were used at the following strengths, 90 per cent of the mustard was 

 destroyed: copper nitrate, 1 per cent; sodium bichromate, 1.8 per cent; 



