Multiple entry holes on avocado trunk. Photo credit: Eskalen Lab, UC Riverside.

Of all the plants in our yard the one I care most about is our avocado tree. I’d be despondent if anything happened to it. Which is why I panicked when I first heard about the Polyphagous Shot Hole Borer (PSHB), a beetle that spreads a fungus Fusarium euwallacea. First noticed in 2003 here in Southern California, the PSHB seems to damage some trees more than others.

Concerned about losing my avocado tree I wrote Akif Eskalen, a plant pathologist at the University of California, Riverside. Dr/ Eskalen’s lab has done a lot of work on the PSHB and what to do about it. I asked him specifically about avocados and here’s what he had to say in an email,

My lab has been conducting a continuous survey on PSHB on infested and non-infested avocados in California since 2012. Based on the preliminary results from our survey the beetle PSHB seems to be attacking and causing damages on primary and secondary branches of avocado only. We have also seen attacks on the trunk of the trees but somehow the beetle is not successful establishing galleries there which could cause of quick death of the tree. I believe with a proper orchard sanitation you can reduce the damage of the beetle and also keep the beetle population down in the orchard . . . we are still continuing experiments with different insecticide and fungicides on avocado against this beetle and their fungi. An insecticide (Hero) has already registered under Section 18 that could be used by growers in CA.

He provided a link to a short publication his lab put out on orchard sanitation best practices as well as a link to information for avocado growers on the use of Hero. Hero is a pyrethroid-based pesticide.

For my own backyard tree I’m going to:

• Make sure pruning tools are disinfected before use. This is one of the main reasons we use a qualified arborist.
• Avoid moving firewood around. I’m going to have to think carefully about the wood I import for my pizza oven.
• Use mulch that has been chipped to less than 1 inch.

I’d sure hate to lose a tree that provides six months worth of free and delicious Fuerte avocados.

Depending on my mood I see our yard either as a sort of groovy, permacultural exercise in “abundance” or as an overpriced rodent feeder. It occurred to me this morning that we’ve been, inadvertently, running an experimental squirrel fruit buffet for ten years.

Perhaps it would be informative to see what trays in the buffet have any fruit left for the resident hominids. Towards that end, I’ve created an annoying, animated emoticon scale ranging from one to five squirrels with five being the most favored fruits and one being the least favored.

In the give up all hope category:

Figs:
Everyone loves figs. Raccoons, squirrels, rats and even Roman emperors. I’ve even seen raccoons, in the middle of the day, feasting on our delicious Mission fig. It’s easy to see why. There’s nothing like a fresh fig. And fig season is so frustratingly short. Kind of like our youth!

Apples:
We have two trees, a Winter Banana and a Fuji. The squirrels are welcome to the mealy Winter Banana apples. But those Fujis are just about the tastiest apple I’ve ever eaten. The squirrels usually manage to get them all.

Persimmons:
We have both the non-astringent and astringent types of persimmons. The squirrels like to take a bite out of them before they are ripe, thus leaving them to rot on the tree. Persimmons take so long to mature that I doubt I’m going to get any this year before the squirrels get to them.

Peaches:
I managed to harvest a few thanks to throwing some netting over the tree. But I was so stressed out by the prospect of finding the tree stripped of fruit that I became unpleasant to live with.

On the more hopeful side:

Avocados:
The damage here is more from rats than squirrels, I think. Typically, I’ll find an avocado with one bite near the stem on the ground. The good news is that those partially chewed avocados are, usually, still edible.

Pomegranates:
I think this is the real winner in the squirrel/human fruit buffet fight. I’ve found squirrels trying to eat them but they have to chew through the thick and unappetizing skin. Plus the tree has hidden, wicked thorns. The downside is that these two qualities also make them difficult to harvest and eat. I use what we call the pomegranate spanking method to release the seeds. Squirrels have not yet figured this out.

What fruits do you manage to wrestle from the squirrels? What have you noticed in your garden?