Apple dimpling bug
Commonly known as the apple dimpling bug (ADB) on mainland Australia, Campylomma liebknechti is primarily a pest of apples. It is a small sap‑feeding insect that damages young fruitlets, causing dimples and deformities that can significantly reduce marketable yield.
Pest identification
Adult ADBs are greenish-brown and about 3 mm long. They have spiny legs, shield-shaped wing covers and dark bands at the base of the antennae.
Damage
Apple dimpling bugs feed by inserting their needle-like sucking mouthpart (proboscis) into the developing ovary of the flower or fruitlet and sucking the sap. The scarring at the feeding site fails to grow as the surrounding flesh expands, resulting in a typical dimple, reducing the fruit's saleability.
Monitoring
The main risk period for ADB is between early pink and petal fall. The danger is increased if fruit tree flowering coincides with, or immediately follows, the flowering of native trees in the surrounding bush, especially tree lucerne (Figure 41), wattle (Figure 42) and Geraldton wax. Monitoring ADB activity in these species in the lead-up to apple flowering can indicate the likely level of seasonal risk.
Monitor ADB numbers at least twice weekly from late spur burst through to complete petal fall by tapping bud and flower clusters over a 4 L white ice cream container (or equivalent). The bugs are very active so the container needs to be inspected quickly to see the bugs before they escape. For most of the risk period (until 100% petal fall), the potential for significant ADB damage is high, even if bugs are present in only low numbers (i.e. 2 to 5 bugs per 250 flower clusters). Be aware that population numbers can quickly escalate to significant levels with weather changes. Experience has shown that ADB numbers often increase following the arrival of warm, northerly winds.
Management
Cultural and physical: maintain vigilance on blocks or rows that neighbour native trees and shrubs. Consider removing nearby host species, particularly lucerne and wattle trees.
Hand-thinning for crop load from late November to early December is a good opportunity to remove any apples with signs of dimpling damage. Some damaged fruit will drop naturally between petal fall and harvest.
Biological: there are no known biological control agents for ADB. Interestingly, after complete petal fall, ADB might actually be a beneficial insect in the orchard, feeding on Helicoverpa spp. moth eggs and pest mites.
Chemical: refer to the Orchard plant protection guide for chemical suggestions.
