85 



THE GOOSEBERRY SAWFLY. 



(Nematus ribesii, Curtis.) 



The Gooseberry Sawfly is a common and destructive pest 

 in most parts of the British Isles. It also occurs in many 

 European countries, in the United States and in Canada, 

 being thought to have reached the two latter countries in 

 soil adhering to the roots of imported gooseberry or currant 

 bushes. 



Plants Attacked and Nature of Damage. The Gooseberry 

 Sawfly occurs most frequently on the gooseberry, but it also 

 attacks red currants, and (more rarely) black currants. The 

 injury is due to the sawfly caterpillars, which devour the 

 leaves (Fig. 1), and in a bad attack strip the bushes completely, 

 with the result that the season's crop may be lost, and the 

 bushes so weakened that they can produce little fruit during the 

 following year. A characteristic feature of the pest is the 

 rapidity with which it increases whenever it is neglected. 

 Too frequently no notice is taken of an attack on one or two 

 bushes when the pest could easily be controlled, and the 

 following year, or even later in the same season, it is found 

 that the whole plantation is attacked, with the consequence 

 that much trouble must be taken and expense incurred in 

 destroying the caterpillars. 



Description and Life-History. The adult sawflies (Fig, 3) 

 first appear in April or May. The female is about one-third of an 

 inch in length, with clear transparent wings, and a body black 

 and yellow in front and yellowish-orange behind. The male 

 is similar but somewhat smaller in size and the upper part of the 

 body behind the wings is black and the size somewhat smaller. 

 Eggs (Fig. 2) are laid by the female on the gooseberry leaves, 

 usually a large number being laid on one leaf (see Fig. 5) ; they 

 are fixed into shallow slits in the surface of the leaf, but are 

 fairly conspicuous. In about a week the caterpillars, which at 

 first are pale green, slightly speckled with black, are hatched 

 from the eggs, and for some days feed together in a colony, 

 first eating the surface of the leaf and then nibbling holes. 

 As they grow older they spread all over the bush, eating the 

 whole of the leaf. They are then sage-green in colour, with a 

 black head and numerous black spots (Fig. 4). When full-grown 

 about four weeks after they have hatched, the caterpillars 

 lose the black spots and are pale green, almost orange behind 

 the head (which is now green) and near the " tail. " At this stage 

 they leave the bushes and make oval brown cocoons (Fig. 5) in 

 the soil, from which, in the summer, the adults emerge in 

 from 10-21 days. There are usually three broods of sawflies 

 in the course* of the season, and if the weather is very 

 favourable (dry and warm) there may even be four. In 

 consequence the pest may increase in numbers enormously 



