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Aug 06

Wildlife Wednesday: Invasion of the Plum Moth

Whilst a big fan of the natural world, as an enthusiastic gardener there are occasions when wildlife comes into conflict with my green fingered efforts.

The gardener in me has been getting very excited this year. For the first time since we planted them, three years ago, our pear and plum trees have blossomed and developed fruit. It does take time for plants to fruit when introduced as maiden whips (otherwise known as a one year old tree with no side shoots to three-years-ago-me) but I had just about given up on them.

As the summer has gone on, both pears and plums have got larger and we have eagerly anticipated our first taste of their fruit. About a month ago, I noticed some of the plums seemed to be ripening prematurely and then going bad and dropping off. I put this down to them dropping due to overcrowding on the branches – our juvenile tree is quite literally dripping with fruit and I really should have thinned them out earlier.

Last week, the first few plums ripened up properly and we prepared to pig out. Biting in to the first of our juicy, purple crop though brought discovery of a coffee granule residue around the stone and fruit damage. Plum after plum was the same and despite nibbling a few lesser affected ones, mainly our precious haul headed for the compost heap. Today, biting into yet another plum I came nose to nose with a tiny pink, brown headed caterpillar. I was not impressed.

Plum Moth Caterpillar

Our Pink Peril caught red-handed (or pink footed).

Looking up this pink peril, it turns out our plum tree has been infested with Plum Moth. An increasingly common pest for reasons scientists are yet to fathom, the Plum Moth lays its eggs inside the young plums and the caterpillars subsequently hatch and munch their way through the fruit during early summer. They then drop off and pupate over winter in bark and the soil below the tree before emerging as moths with the warm weather the following year.

I’ve had a good hunt for ways to tackle our Plum Moth problem. Disappointingly there is not much we can do for this year’s crop. As the Plum Moth usually only has one hatching cycle a year there is a good chance our later ripening fruit will be less affected although in warm summers the Plum Moths can have time to lay more eggs.

To prevent a re-infestation of Plum Moth next year there are a few things I’m going to try. With young children and an appreciation of the natural world I don’t want to go down the route of sprays or chemicals but there are a few ideas I’ve found to try and prevent such a serious re-infestation next year:

  • Remove all bad fruit, including windfalls, and destroy or dispose of well away from the tree. This helps to reduce the number of caterpillars emerging as moths near the tree to continue the cycle next year;
  • Dig lightly to disturb the soil round the base of the tree in early spring next year. The theory goes that this might disturb the ground that the pupating Plum Moths are cocooned in and make them more accessible to birds and other predators, reducing numbers of caterpillars emerging;
  • Hang up pheromone traps in early summer. These release the pheromone scent that is attractive to the male moths. It won’t get rid of all the moths but will give you an indication of how serious your infestation is and hopefully reduce the number of breeding moths a little;
  • Apply a horticultural glue band around the base of the tree from spring into winter. This can help stop female moths who reportedly sometimes prefer climbing to flying into the tree and can also help reduce any caterpillars heading for the ground to overwinter. I’m a little sceptical on the science behind this one but who knows, maybe it could help?
  • Befriend wasps. Yes, I know, the same wasps that plague the garden picnic… they, along with bats and birds are actually a natural predator of the Plum Moth. They also prey on other garden pests too so tolerating wasps is actually good for the garden.

If you have any other ideas for controlling the Plum Moth in an environmentally friendly way then please send them my way. Maybe next year we might finally get to enjoy a plum or two!

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