If I can tag on a question of my own: My books say that gooseberries
don't need pruning, but in recent years I've had a dramatic downturn
in quantity of fruit, with or without caterpillars, and the bushes are
straggling a bit. Does the panel thing that pruning would improve
yield, or at least not reduce it any more?

From what I've read, they fruit better on younger wood, so you could try
cutting out some of the old gnarly branches.
--
Kay