Polyphagous Shot Hole Borer and Avocados

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

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.

What’s the Most Squirrel-Proof Fruit?


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: Squirrel Icon by AlephronSquirrel Icon by AlephronSquirrel Icon by AlephronSquirrel Icon by AlephronSquirrel Icon by Alephron
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: Squirrel Icon by AlephronSquirrel Icon by AlephronSquirrel Icon by AlephronSquirrel Icon by AlephronSquirrel Icon by Alephron
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: Squirrel Icon by AlephronSquirrel Icon by AlephronSquirrel Icon by AlephronSquirrel Icon by AlephronSquirrel Icon by Alephron
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: Squirrel Icon by AlephronSquirrel Icon by AlephronSquirrel Icon by AlephronSquirrel Icon by Alephron
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: Squirrel Icon by AlephronSquirrel Icon by Alephron
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: Squirrel Icon by Alephron
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?

How to Squirrel Proof Your Fruit Trees

IMG_7297We’ve been guilty in the past of claiming that growing fruit is labor-free. That’s a lazy blogger’s lie. The truth is that you have to stay on top of pruning, irrigation, fruit thinning, fertilizing and pest prevention if you want to harvest any fruit. After not getting a single peach off our small tree last year due to squirrels, I vowed to do things differently this year.

I considered a number of squirrel prevention techniques:

  • Metal collars on trunks. This doesn’t work, especially in urban areas. Squirrels are superb acrobats and can simply jump from a roof, fence or adjacent tree on to your fruit tree.
  • Trapping, killing, hunting. I don’t have the heart to do this and it’s illegal in urban areas but it is what professional orchardists do.
  • Electronic or visual frightening devices. According to UC Davis, these don’t work. Squirrels aren’t dumb.
  • Dogs. Maybe, but it depends on the dog. Our late doberman was more interested in alerting us to the mail carrier’s rounds. He was more interested but, ultimately, unsuccessful in his 13 year battle against skunks.

Exclusion with plastic bird netting is the most promising technique for urban areas. In order to do this you need to keep the tree pruned to a manageable size. I purchased a 14-foot by 14-foot piece of bird netting and Kelly and I put it on the tree (it’s a two-person job as bird netting is a pain to work with). We secured it with clothes pins. You must be absolutely certain to leave no gaps in the net. If you leave a gap you could trap birds and the squirrels will also work their way in. The next step is to keep a close eye on the fruit and harvest it as soon as you can, perhaps a little sooner than is ideal.

Unfortunately, squirrels can easily chew through bird netting so this method is far from foolproof. According to UC Davis, exclusionary methods will only work if the squirrels have other things to eat. Another argument for biodiversity in our landscapes, I suppose.

If you know of any foolproof squirrel prevention techniques please leave a comment!

Coffee Grounds in the Garden

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According to a handy fact sheet from Washington State University, Coffee grounds will buzz your garden. Coffee grounds build humus, boost nitrogen, phosphorus and zinc, bind pesticides and toxins, prevent bacterial and fungal infections and feed earthworms. Authored by Dr. Linda Chalker-Scott, Extension Urban Horticulturist and Associate Professor, this peer-reviewed pamphlet also provides a set of suggestions for using coffee grounds in the garden:

  • Coffee grounds should be composted before used as a soil amendment but can be used fresh as a mulch.
  • Fresh grounds are phytotoxic, so keep them away from direct contact with roots.
  • Coffee grounds will not necessarily make your soil more acidic.
  • Don’t use coffee grounds where you are starting seeds.
  • Despite rumors, coffee grounds do not repel pests.
  • Let coffee grounds cool before adding to compost bin so you don’t kill beneficial microbes. And don’t let coffee grounds amount to more than 20% of your compost pile.
  • Don’t add coffee grounds to vermicomposting bins.

If you’re using coffee grounds as a mulch Chalker-Scott has two suggestions:

  • Apply a thin layer (no more than half an inch) of coffee grounds. Cover with a thicker layer (four inches) of coarse organic mulch like wood chips (Chalker-Scott 2015). This will protect the coffee grounds from compaction.
  • Don’t apply thick layers of coffee grounds as a standalone mulch. Because they are finely textured and easily compacted, coffee grounds can interfere with moisture and air movement in soils.

How to Rodent Proof a Chicken Coop


One morning I opened the metal trash can I used to keep the chicken feed in and plunged a scoop into the feed. In that cup of feed there was some additional protein in the form of a small, freaked-out mouse. I shrieked and the mouse jumped out of my hand and dashed off. Then I peered into the bag of feed. Like the plot of a rodent horror movie, I found two other mice running around along with a dead and bloody mouse. I’ll leave it to you to fill in the mysterious details of that story. But I knew it was time to deal with the problem.

Thankfully, like Dr. Maurice Pitesky mentioned in the podcast on Wednesday, most chicken pest problems can be taken care of with simple sanitation. In my case that meant putting the food away at night and investing in rodent proof feed containers.

Every night I put the entire feeder within the trash can you can see in the picture on the right (it has a much more secure lid than the larger can I used to keep the feed in). In the morning I put the food out again for our four hens. It means that I have to get up just a few minutes earlier than I usually do but that’s not a big deal as I’m one of those tedious and boring morning persons.

Some folks use rodent proof treadle feeders. These feeders open when the hens step on a small metal platform. I was sent a treadle feeder like the one above but my skittish hens would not get anywhere near it even with the treadle kept open. I probably could have trained them to use it but I’ve found that putting the feed away at night is no big chore. I gave the treadle feeder away to some other chicken enthusiasts whose hens are less afraid of the contraption.

As to rodent-proof feed containers I’m using two Vittle Vaults, one for the feed and the other for scratch. They have a locking, rodent and water proof lid. The small trash can in the picture (that I put the whole feeder in at night) seems to be working.

For more information on controlling mice and rats see UC Davis’ Integrated Pest Management information for rats and house mice. We used to have mice in the house but the cats have taken care of that problem. As to the issue of rodents eating fruit, I’m still working on that problem.