Fruit growers are warned to be on the alert for a new pest spreading through New Zealand. The fruit driller caterpillar (FDC), Coscinoptycha improbana, also known as the guava moth caterpillar, burrows into and spoils a wide range of fruits.
In New Zealand, it has so far been identified in citrus, macadamias, feijoas, nashi pears, guavas, loquats plums, peaches and possibly apples. An infestation is virtually undetectable from the outside. The only sign is a 1mm hole left by the caterpillar when it leaves the fruit to pupate in the ground.
First identified in Kaitaia in 1997, FDC has been spreading south and now NZ Tree Crops Association (NZTCA) has reports of infections in the Waikato. In 2001, MAF decided not to try and control this pest. By then, it had already spread over an area it considered too large to target. It was also thought possible it could have arrived by wind from Australia and could do so again. It is not considered a pest there, presumab;y because it has a natural predator there. However, NZ growers are concerned and the multiple lifecycles each year and wide variety of fruits affected means control needs to be year round.
At this time, it is not known if this pest can be killed by spraying, but with a life-stage inside and protected by the fruit, it is thought this will not be very effective.
NZTCA has commissioned research to develop a pheromone to attract, and therefore trap, male moths, but this is not ready for commercial production yet.
President Murray Redpath says it is very easy for this pest to move throughout the country when unsuspecting people carry infected fruit. For further information see www.treecrops.org
Sheryn Clothier, NZTCA publicity officer.
Our Plant Doctor Andrew Maloy has had several quest-ions from readers about this pest, suggesting it is becoming a significant problem for gardeners. He recommends picking up all fallen fruit very regularly and also removing any other litter under trees where the moth pupates. If anyone has suggestions about ways to combat it, I’m sure other readers would love to hear them – Susie.
