We’ve had a reduced crop of gooseberries this year but it could have been far worse. The reason for this is the voracious appetite of the gooseberry sawfly (Nematus ribesii). Do not be misled by their small, innocuous appearance. The gooseberry sawfly caterpillar is a monster. Its a major pest. It can strip a gooseberry bush of its foliage in a day. There is a place in the world for all of creation but so there is also the unfettered enjoyment of home grown gooseberries.
One of my gooseberry bushes was on the way to being stripped bare. Luckily the two neighbouring bushes appeared unaffected. Closer inspection revealed a small luminous green caterpillar with small brown spots, about one centimetre in length, happily munching away on the underside of a leaf. Then I spotted another, and another, and another... .
The adult sawfly lays its eggs on the underside of the leaves usually at the base of the plant. This means they are likely to be unnoticed until the damage to foliage becomes overt.
Never one to use chemical interventions, the first step was to meticulously pick off each of the intruders I could find. Prickly work! Next a solution of soapy water was applied in a fine spray. I repeated this for the next four or five days (tedious but essential). The result was that after a week I could see no further sign of them. To my relief none of the neighbouring bushes had been affected. I gave it a good watering and feed in the form of pelleted chicken manure and although it looks a poor specimen new foliage has started to appear.
You have to remain vigilant as the sawfly reproduces rapidly and three generations can be produced during the course of the summer with the consequent risk of a re-infestation. Watch out for currant bushes also, as they like those too.