Borers on Torrey Pines

Question from Allen: i have a boring insect on my torrey pines, not sure what it is but the trees are dying, is there something i can do to save them?

Answer from Pat: Several types of boring insects attack Torrey pine. Once borers have gone all the way around the trunk of a tree girdling the cambium layer this will kill the tree and nothing you can do will save it. The best defense is to water and care for the tree so that it can drown out the pests itself with sap.

The first line of attack is to have a healthy tree in the first place. If you are living in a place with very poor soil or no water and a dry interior climate this is not good for Torrey pine trees. They prefer a coastal climate. However, we have had good rains this year so it stands to reason your trees have had adequate water this winter. My guess is that the trees have been suffering from borers for a long time and now is when the problem rears its ugly head. Is it also possible that they suffer from poor drainage in heavy clay soil? If so, apply gypsum to the soil as if a light snow had fallen and water it in. This might help but takes time to work. Also make sure the trees are well mulched and allow the needles to stay on the ground where they fall. Given good drainage Torrey pines can accept more water than is commonly supposed. Adequate water and good drainage makes them grow healthy and green. Too much shallow water causes shallow roots and can tip them over in wind.

If I were you I would attempt to save the trees by spraying the trunks with a homemade mix of fertilizer and earthworm castings. For example you could mix up a bucket of fish emulsion according to package directions and mix in a cup of earthworm castings and spray that on. If some reaches the borers the earthworm castings might cut down their numbers. The fish emulsion could reach the cambium layer and feed the tree. Additionally I would soak the ground under the drip line (branch tips) with humic acid and liquid kelp mixed with alfalfa tea. Alfalfa tea seems to be a remarkable tonic for plants and humic acid releases the nutrients already in soil while kelp provides trace elements. Look in my book on page for a recipe for alfalfa tea on page 119. All this might give your trees the oomph to pull through.

One time years ago a neighbor of mine said she feared her Torrey pines were going to die. I went to look and they were fine. All they were doing was dropping their old needles as they put on a whole lot of healthy new ones. This made her trees look temporarily a bit yellow and sick. This does not occur, however, until early summer. In April, which is now, the trees should look very green and healthy.