Black Stem Borer

Folks may be aware that in the northeast - at least - we're dealing with a relatively new apple pest called the black stem borer. The BSB is a small ambrosia beetle that bores into the trunk of the tree, lays its eggs, brings in fungi to feed the kids, and then back half way out and dies. The BSB is attracted to trees that are under stress (the trees emit ethanol when under stress) and is particularly attracted to high density dwarf trees that are under stress. And as you can imagine trees with smaller root systems can come under stress a lot easier than larger trees. There are not many good controls even for conventional growers, much less organic or holistic growers. The best advice is to not allow your trees to become stressed. However, with no way to measure that - how much stress it too much? - and that growers are generally working to not stress their trees (at least not too much), my questions are: does anyone have any novel ideas for measuring stress and/or controlling boring ambrosia beetles (specifically black stem borer) and/or reducing the pathogenicity of the fungi the young feed on? Here's an article about the pest: Black Stem Borer

Mike Biltonen, Know Your Roots
Zone 5b in New York

I've lost 5 or 6 trees to this pest so far. Last year I started doing the neem oil trunk spray every two weeks. From April to October. That worked very well, however this season I got a late start and two trees were hit. One died and one is in recovery.

I've read that you can make traps for these guys with a large water bottle and some ethanol. I have yet to try it, maybe next spring.

Opening this thread back up again as we've trapped higher levels of this new (to us) insect this past growing season. Anyone else have advice? What have people tried in the past few years?

Thanks in advance.

Door Creek Orchard
Zone 5a in Wisconsin

Hi Liz,
Can you give us a little more information?

- How are you trapping them?
- How many individuals are you trapping and how often?
- Are you identifying them to species? There are other ambrosia beetles that are non-pest species in apples.
- Where are finding them in the trees?
- Variety, rootstock, tree age, etc.?
- Lastly: have you done anything to date to try and control them either pre- or post-damage?

There isn't a whole lot of new information in general about them, but the specifics of your situation might help better understand a forward path.

Thanks, Mike

Mike Biltonen, Know Your Roots
Zone 5b in New York

Mike -

We participate in a monitoring program through DATCP and IPM Pathways; they do monitor trapping for new invasives at our place and several other orchards in the area. I don't have the answers to some of your questions but I could inquire.

Here are the numbers for the two traps on our property this past year (one each in our two biggest blocks):

Trap set 05/15/20, Trap down 09/15/20: 726 BSB
Trap set 05/15/20, Trap down 09/15/20: 320 BSB

They were pheromone-baited traps. The insects were identified by DATCP entomologist at the Plant Industry Lab in Madison. Any suspects were sent to a USDA identifier for official confirmation. They did not give me a breakdown on how many times they checked the traps during the period the traps were up, but they did mention that most were collected in the two weeks from June 1-15. They also mentioned that there appears to be a second emergence in August.

I have not ever noticed BSM myself on our trees, but I have not been actively scouting for them. This goes for confirmed damage from them as well. And so I have not actively tried to treat for them.

Based on this new information I had planned to start specifically looking for them this year, especially on our dwarf trees. We are a small (about 9 acres currently planted), well established, very diverse orchard - our trees range greatly in age, rootstock, variety, density, system etc.

Age: oldest trees planted in the 1970s, bulk of trees planted between 1986 and 1995, continued various planting from 1995 through 2020.
Rootstocks: seedling, MM111, B118, MM106, M7, Mark, M26, B9, G30, G11, G16, G41, G935, G890, G202
Varieties: about 90 - there is a list on our website if you feel that would be helpful.

Door Creek Orchard
Zone 5a in Wisconsin