There’s slugs on my fruit trees!

Have you seen these critters on your fruit trees?

Pear and cherry slug
Pear and cherry slug

These are pear and cherry slugs, and as you can see, they eat the leaves on pear and cherry trees.

The first question to ask yourself when you see these creepy looking slugs (as with all pests and diseases on our fruit trees) is, how much damage are they really doing?

One of the advantages of keeping a close eye on your trees is that you will often notice problems as soon as they occur, and can then take simple action, like squashing the slugs between a folded leaf.

Getting rid of Pear and cherry slug the manual way - by squashing them in a leaf
Getting rid of Pear and cherry slug the manual way – by squashing them in a leaf

In a normal season, this particular pest will go through at least two life cycles, so the more of them you squash as soon as you see them, the more you interfere with their natural life cycle and can prevent numbers building up.

Squashing Pear and cherry slug without damaging the tree
Squashing Pear and cherry slug without damaging the tree

Fruit trees can actually tolerate quite a bit of damage without losing function or growth – our rule of thumb with pear and cherry slug is that if a tree has lost more than 30% of its leaves, that will be our trigger to treat them, and in all our years of growing, we’ve closely monitored every year, and never had to take action against them.

Ewwww .... squashed slugs
Ewwww …. squashed slugs

Usually what we find is that if we are patient, a predator insect will come along and do our work for us, leaving behind a dry, parasitised slug as you can see on the leaf below.

A Pear and cherry slug that's been parasitised
A Pear and cherry slug that’s been parasitised

So pear and cherry slug is a great example of learning how to watch our trees and learn what’s really going on, rather than assuming that if there’s a bug, there’s a problem!

If you want to find out more about the life cycle of the Pear and cherry slug, as well as how to treat and prevent them, check out “What’s Bugging My Fruit?“.

Why you should pick up fruit from the ground (yes, all of it!)

One of the easiest—but most important—things you can do to control both pests and diseases in your fruit trees is to pick up all (yes ALL) the fruit that falls during the season.

We call this practice “orchard hygiene”.

Apricots rotting on the ground under the tree
Apricots rotting on the ground under the tree

This is a common sight under apricot trees — fruit that has fallen because it’s damaged by birds, or overripe. Once on the ground, it will usually then develop Brown rot.

This is normal—fungal diseases like Brown rot are incredibly useful in the ecosystem in returning organic waste to the soil. It may seem counter-intuitive to remove this great source of organic matter for the soil, and seems to go against the ‘closed loop’ principles that permaculture teaches (which we practice here on the farm as much as possible).

However, we don’t want the Brown rot to spread to healthy fruit on the tree this year, or to infect our trees next year, so it’s important to pick the fruit up and completely remove fallen fruit from the area.

Where permaculture principles come into play is what happens next.

We collect ours and feed it to animals, either on the farm or nearby farms (and the farmers are always very happy to get some supplementary organic feed for their animals).

Other options like putting the fruit through a worm farm or hot compost system will also ‘clean’ the fruit and allow the organic matter to be returned to the soil.

If you want to learn more about how to use permaculture to increase the amount of food you grow, check out Permaculture in Action.

Here’s some other reasons not to leave fruit under your trees. It provides the perfect breeding ground for the following pests:

(a) carpophilus beetle – a tiny beetle that puts tiny holes in fruit, and is also a carrier of the Brown rot fungal spores.

Tiny carpophilus beetle on an apricot
Tiny carpophilus beetle on an apricot

(b) earwigs – fruit on the ground provides a good food source and breeding ground for earwigs, which are one of the worst pests of stone fruit:

A cluster of earwigs inside an apricot
A cluster of earwigs inside an apricot

(c) Queensland fruit fly – we don’t have these in our district (yet), but it’s a terrible problem in many fruit growing areas, and relies on fruit and vegetables for its food source.

A lemon that's been infected by Queensland Fruit Fly
A lemon that’s been infected by Queensland Fruit Fly

They won’t infect fallen fruit, but if they’ve already laid eggs in the fruit before it falls, the fruit on the ground provides the perfect nursery habitat for the next generation.

Did you get the thinning right?

As we go about picking in the orchard during the apricot season, we see the end result of the thinning that was done a couple of months ago – where it worked, and where it didn’t.

Here’s a bunch of apricots that were missed in the thinning, and you can clearly see the outcome.

Bebeco apricots that were missed in the thinning
Bebeco apricots that were missed in the thinning

Out of this bunch of four, two apricots have grown normally, and two are stunted, slightly shrivelled, and not really edible – these are the ones that should have been removed when we were doing the thinning.

Apricots that have been thinned properly
Apricots that have been thinned properly

When they’re removed, you can see that we’re left with two reasonably sized, delicious looking apricots. But…how much bigger could they have been?

The energy that the tree has put into the two discarded fruit would have been better put into growing just two pieces of fruit in the bunch to a larger size.

This is just one reason why it’s a good idea to do thinning early, hard, and thoroughly! We’re aiming to always maximise the ratio of usable, edible fruit to core/stone that the tree produces.

It’s also distressing to see broken laterals like this in your fruit tree.

Broken laterals in apricot tree due to under-thinning
Broken laterals in apricot tree due to under-thinning

This is another problem caused by leaving too much fruit on a branch that isn’t big enough to carry the weight. Unfortunately once the lateral is broken, not only have you lost an important part of the fruit-bearing part of the tree, but the fruit growing on that lateral is usually wasted as well.

Thinning has so many benefits for your tree, and your crop, but a lot of people are scared to do it for fear of taking off too much fruit, too little, or just generally getting it wrong. The Fruit Thinning Chart (unit 4a out of the 12 units in the Fruit Tree Thinning short course) will guide you through this.

Having put all your care and attention into growing and pruning the tree, it’s then such a pity to damage the tree just by leave more fruit on any one branch or lateral than it can carry.

Sorry, tree…