Why Have My Currant Leaves Been Completely Stripped?

A currant bush that appears to lose its leaves almost overnight — going from fully leafy to bare stems in just a few days — has been attacked by currant sawfly larvae (Nematus ribesii and related species). This is one of the most destructive pests of currants in temperate gardens, and the speed of the damage frequently catches growers off guard. The larvae are voracious feeders that can completely defoliate a bush before most people notice they are present, because they start feeding in the interior of the plant where they are initially hidden from view.

Identifying currant sawfly larvae

The larvae are pale green with black spots along the body, roughly 2 cm long when fully grown, and they move in groups on young leaves. The adult sawfly is a small yellow and black wasp-like insect that is rarely noticed — it is the larvae that cause all the visible damage. Look inside the bush at the central branches and lower leaves in mid-spring; this is where eggs are laid and where the first infestation typically begins before spreading outward.

Hand-picking

For small to medium-sized infestations, hand-picking is effective and avoids any pesticide use. Wearing gloves, check the bush thoroughly two or three times per week from late April. Remove groups of larvae — they are often clustered on a single leaf — and drop them into a bucket of soapy water. Repeat checks are essential because new batches of eggs can hatch throughout the season, with up to three generations per year in warm climates.

Organic and conventional controls

Where hand-picking is insufficient, a pyrethrin-based insecticide or spinosad product applied directly to the larvae is effective and has a relatively short environmental persistence. Apply in the evening when pollinator activity is lowest, and do not spray open flowers. Conventional synthetic pyrethroids are also highly effective but more harmful to beneficial insects — reserve these for severe infestations. Always read the product label and observe any pre-harvest intervals.

Recovery after defoliation

A healthy, well-fed currant bush will usually recover from one complete defoliation in a season — new leaves will emerge within two to three weeks. However, a bush that is defoliated twice in the same year, or one that was already under stress, may be severely weakened with poor bud formation for the following year. After an attack, water and feed the bush generously to support recovery. Apply a mulch to conserve moisture and provide a slow nutrient top-up over the remainder of the season.