1132 



The Turnip Gall Weevil. 



[Mar., 



out of the gall to pupate except after the soil around has been 

 well moistened by rains. About five to six months are spent 

 in the larval stage. The pupal period varies and is short for 

 those that cocoon late owing to the warmer conditions. The 

 adults emerge late in May or early in June. 



Host Plants. — The cultivated plants known to be attacked 

 include turnip, mustard, rape, cabbage, Brussels sprouts, cauli- 

 flower, kale, and kohl-rabi. 



Natural Enemies. — This insect has various natural enemies. 

 The common garden slug may bore into the galls and feed on 

 the grubs along with the plant tissues. The grub of the turnip 

 mud beetle (Ilelophorus rugosus, 01.) preys on the weevil larvae 

 and will bore into the galls to get at them. A small parasitic 

 wasp (Diosjnlus oleraceus, Hal.) lays its egg through the gall 

 into the grub and its larva lives inside it, ultimately killing 

 it, Certain birds pick the grubs out of the galls and feed on 

 them. 



Methods of Control.— (1) Root out all infested stalks that have 

 been wintered over by the beginning of March, and of spring 

 cabbages as early as possible, and immediately stack them up in 

 large loose heaps. This is the time when the grubs are nearly 

 full-grown and begin to bore out into the soil to pupate. They 

 go into the soil, however, only when it is quite moist and by 

 stacking the stems as advised above the full-grown larvae are 

 kept back in the first place and as the bark dries quickly they 

 find it impossible to bite through the hard bark to go into the 

 soil. The rest are half grown larva? and these slowly shrivel up 

 in the bark as it dries. Never leave infested stalks in small 

 lots or scattered about for any length of time. 



(2) Plough the land deeoly immediately the infested crop 

 has been removed. This operation will crush and destroy 

 numbers of cocoons with the pupa? within. This is very neces- 

 sary where such crops could not be removed at the early date 

 suggested. 



(3) Avoid in the next autumn planting another crop that is 

 likely to be attacked. The summer race lays its eggs from 

 about the end of August through the autumn. 



(4) Destroy all charlock and hedge-mustard, as the adult wee- 

 vils feed on these, and as it may be possible that some of the 

 beetles emerging early from the spring race that breeds in 

 charlock may lay eggs in the cultivated plants in autumn. 



