1130 



The Turnip Gall Weevil. 



[Mar., 



manure highly contaminated with vegetable refuse there is no 

 reason to expect further serious outbreaks. Where Pink Rot 

 has occurred diseased haulms and tubers should on no account 

 be left lying about and especially not allowed to reach the 

 manure heap. 



Irish and Scotch growers should take steps to eliminate the 

 disease as far as possible, both from seed and ware crops. 

 The great lesson to be learned is the importance of accurate 

 knowledge with regard to all these diseases both on the part of 

 those whose duty it is to undertake research and of those who 

 grow the crops. Any doubtful cases of this or other diseases will 

 be reported on if specimens are sent either to the Adviser in 

 Plant Pathology at the local Agricultural College or to the 

 Ministry's Pathological Laboratory at Harpenden. 



THE TURNIP GALL WEEVIL. 



P. V. Isaac, M.Sc, F.E.S. 

 Imperial College of Science and Technology. 



The turnip gall weevil (Ceuthorrhynchus pleuro stigma, 

 Marsh.) is a small beetle injurious to turnips and cabbages, 

 being the cause of the smooth rounded outgrowths, known as 

 galls, on these plants. The galls are the abode of the young of 

 these insects. These bear no resemblance to their parents and 

 are known as grubs or larvae. The insect is distributed through- 

 out the United Kingdom and is also found on the Continent. 



Description and Habits. — The weevil is about J in. in length, 

 and is black above and greyish below. During summer and 

 autumn they may be seen in numbers, but one has to look for 

 them carefully as, in addition to being very small, they always 

 attempt to remain concealed and when disturbed drop into the 

 soil and lie motionless on their backs. They generally feed on 

 the leaves, tender bark, young pods and flowers of turnips and 

 cabbages, and the foliage and flowers of charlock and hedge 

 mustard. They rarely expose themselves and are usually found 

 on the lower surface of the leaves of the plants mentioned above 

 or in the soil at or close to the roots of the plants in the roots of 

 which they lay their eggs. 



The egg is a very minute, soft, almost transparent object, 

 and is laid in a cavity drilled by the parent beetle in the bark 

 on the root of the host plant, see Fig. 2. One female beetle lays 



