Indications of a plum moth include;
- Fruits with a caterpillar inside usually ripen early and are often slightly misshapen. This should not be confused with pocket plum, a fungal disease affecting plum fruits
- The caterpillar inside the fruit is up to 12mm long and is pale pink with a brown head
- There will be many light brown excrement pellets near the plum stone where the caterpillar has been feeding
- Infested fruits tend to ripen first, fruits that ripen later on the tree often have a much lower incidence of the caterpillars
A resinous gum around the stone is a physiological disorder and should not be confused with plum moth damage.
Plum sawfly is a less frequent on plums than plum moth. The larvae tunnel into three or four fruitlets before going into the soil to pupate. Unlike plum moth whose caterpillar develop in the mature fruit, fruitlets damaged by plum sawfly fall from the tree at an early stage in June.
The plum cultivars ‘Czar’ and ‘Victoria’ seem to be more susceptible than others to plum sawfly.