Imported currant worm

damaging

Red currants and gooseberries can be bothered by imported currant worm (Nematus ribesii), a type of sawfly.
The adult emerges from the soil in June and lays eggs on the underside of the leaves. The eggs hatch into larvae which feed on leaves - fortunately they leave the fruit alone. The larvae are voracious eaters and can defoliate a plant if the numbers are high. After gorging, the larvae drop to the ground and burrow into the soil to pupate and overwinter. These pests are actually quite simple to control.
Control:
  • Install row covers in early June to prevent adult sawflies from laying eggs.
  • Check the underside of the leaves for eggs in mid-June (if no row covers used) and squish them before they hatch. The small, elongated, opaque white eggs are laid in rows along the ribs of the underside of the leaf.
  • Hand pick and/or knock large off the larvae with a strong spray of plain water. Destroy and put in the garbage.
  • Place a tarp under the shrub to catch the larvae as soon as you notice them. Sweep them up with a dustpan and destroy. This interference prevents the larvae from burrowing into the soil where they pupate and overwinter.

 

Source:

Williams, S.; Skinner, H. (2011). Gardening, naturally: A chemical-free handbook for the Prairies. Regina, Saskatchewan: Coteau Books.