Ambrosia beetles are not supposed to use Citrus as a host! This is crazy. If I injected as many holes as I could find with Spinosad do you think it would help?

If memory serves, isn't there a " pin-hole borer" that attacks peaches and apples? I think they are not fatal like peach or flat head borers. Could be anything; I had problem with "pacific flat head borers "in my apple trees a few years back, and I'm in NC. I used the Bayer systemic, but now they say not to on fruit trees.

I don't see how spraying could hurt. I have heard of people digging them out but not sure that helps either. I hate to make preventive sprays because of the damage to beneficials but prevention is the only way to not have an ambrosia beetle problem. They say healthy trees are less likely to have a problem. No guaranty on that either. Sorry about your problem. I'm guessing it's much worse on smaller trees. Systemics are thought to have no effect because no poison gets in the woody trunk and stems. The systemic poison goes to the leaves only I guess. I think the pin head borer is very similar. Tom

If the product is a true systemic, and not a locally systemic insecticide, then it should be found in the xylem and phloem of the tree. Once the borer eats through the phloem he should get a dose of the insecticide. Since the phloem is just under the bark, and transfers nutrients from the leaves and other green tissue to the roots and other parts of the plant, a foliar spray should be good enough to control the borer. If they are already present and feeding deeper into the plant, then a soil application should be more effective than a foliar spray since the xylem is deeper in the trunk than the phloem and transports from the roots to the top of the plant.

I just read that the only class of insecticide that seems to work are the pyrethroids, like bifenthrin. They would need to be applied as a foliar spray with a sticker, and must be applied before they begin to bore.

I hope it is the Pin Head Borer as they seem to do less damage to the tree. The frass pile was small and the PHB bores out of the tree leaving a small frass pile. I cannot find any beetles anywhere so I am going to tape up some sections of bark. If a hole appears in the tape it should mean it is the PHB. The good news is that it has a one year life cycle and I should be able too get it under control.

From my research the Ambrosia beetle does not attack Citrus BUT neither does any of the other borers!!!

The frass left does not look like a beetle that has burrowed in but one that has burrowed out. Small frass verses long string of frass. The Pin hole beetle does that and it is generally not fatal to trees. It has a one year life cycle which means I can prevent the next generation if I'm right. I will treat for all beetles and hope I'm not to late.

I also wanted to add that all this grief is directly attributed to me not finishing my cold protection irrigation. This will not happen again. I am installing it now and have 50% of the trenches dug. If I had of used a trunk spray and a canopy mist my trees would not be dead.