REPORT OF THE ENTOMOLOGIST AND BOTANIST 



235 



SESSIONAL PAPER No. 16 



The Potato-stalk Weevil is a small, slaty-gray, oval beetle about \ inch long, with 

 a black head and beak. There are also three distinct black spots across the shoulders. 



Tbe injury is done by the 

 grubs, of which from one to 

 five may be found during July 

 and August in the stems of 

 infested potatoes, the centre 

 of which they have eaten out. 

 The oval white eggs are laid 

 by the females in slits which 

 they make with their beaks in 

 the base of the stem. The 

 eggs soon hatch, and by about 

 the middle of August the soft, 

 yellowish white, legless and 

 wrinkled grubs with brown, 

 horny heads are full grown. 

 These, like most weevil larvae, 

 lie in the stem in a curved 

 position. Where there are 

 several of these grubs, most 

 of the central part of the 

 stem is eaten, the leaves turn 

 yellow and the stem dies pre- 

 maturely ; but, when only a 

 single larva occurs, little harm 

 is done. When full grown, 

 the grubs usually work their 

 way down to the base of the 

 stalk and form white cocoons 

 of fibres gnawed from the 

 stem. The pupa state is of 

 short duration. The beetles 

 mature in August and Sep- 

 tember, but they pass the 

 winter in the cocoons, and do 

 not emerge until the follow- 

 ing spring. 



The Potato-stalk Weevil 

 has never before been re- 

 corded from Canada as a seri- 



Fig. 11. — Potato vines eaten out by the Potato-stalk Weevil — 

 somewhat reduced. (Kindly lent by Dr. J. li. Smith.) 



ous enemy, but in several of the United States it has occurred intermittently, and has 

 done much harm for a year or two and then suddenly disappeared. It was treated of 

 by Dr. Thaddeus Harris fifty years ago as a potato pest in Pennsylvania. Since that 

 time several of our American practical entomologists have mentioned it in their wri- 

 tings. 



Remedy. — From the fact that the perfect beetle passes the winter in the dead 

 stems of the plants it has attacked during the summer, an easy and effective remedy 

 is to destroy all vines as soon as they are seen to be infested or as soon as the potatoes 

 are dug up. The advantage of promptly destroying with fire all haulms, tops, vines, 

 &c., of such crops as have been taken in, cannot be too strongly advised. Not only is 

 untidy or objectionable litter thus removed and turned into useful fertilizing ele- 

 ments, but many injurious insects and fungous diseases are done away with, which 

 would endanger the crop of the following year. This is particularly the case with the 

 potato, the most destructive disease of which, the Potato Rot, propagates in the leaves 



