The first sign of the infestation of the Plum sawfly, is a small hole in the plum - surrounded by sticky substance on the surface surrounding the hole.
Inside the affected plum, you will find the maggot of the Plum Sawfly - around 1 cm long, creamy in colour.
Commercially, Calypso has been seen to give a degree of protection when sprayed at the end of flower cycle - ie as the petals of the Plum blossom fade and drop.
This interrupts the cycle of the Plum Sawfly larvae entering and surviving in the developing fruit.
Cultivation of the soil - early in the spring, brings the overwintered pupae to the surface. A resident Robin will do the rest for you!
As the last petals drop, then the Plum Sawfly larvae tunnels into the emerging frit of the plum tree. After being fully fed, the larvae then drops to the ground, forming a cocoon - using earth particles so difficult to find!
It remains in the ground at a depth of around 5-6 cms, then pupates in February-March, ready to emerge as an adult Sawfly - in March - April, the female ready to lay its eggs in the Plum Blossom. Affected fruit drop and fall to the ground, where the life cycle of the Plum Sawfly continues as above.
Affected fruit will typically have 2-3 small holes.
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