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Don’t Panic, It’s Organic: Organic controls for ambrosia beetles

Andy Lopez, Contributing Columnist/Invisible Gardener
9:50 am PDT June 24, 2014

In my previous article on the Polyphagous shot hole borer ambrosia beetle I covered the basics of how the beetle decides where to start a fungus crop and to lay its eggs. The long term prevention is to get the Brix level of the tree to it’s maximum, keeping in mind that the higher the Brix level, the higher the minerals and carbohydrates. 

The over all protective ingredient is the high carbohydrates, which will keep the beetle from succeeding in this process. The fungus will not grow if the mineral levels and carbohydrate levels are high enough. 

It is important to use natural sources of these minerals and not to attempt to be a chemist and supply it directly, as this will lead to over use and it will kill the tree.

When checking for Brix level use the leaves or flowers of the tree. Measure the Brix level of the tree and not of the fruit or juice.

Here are some organic controls that can be applied to the tree to kill the beetle and to prevent the fungus from growing, which will kill the beetle on contact: 

• Caffeine — Caffeine can be applied in several ways. If you only have a few trees, you can place three tree vents around the base of the tree, approximately three feet out from the trunk. A tree vent is what I call it, but it is either a four inch-wide clay drain pipe or a simple pvc pipe, four inches wide and 18 inches long. Put a grate on top and place a drip line around the trunk so that you can place a one gallon per hour drip head on top of the vent. Inside the vent place the following mixture:

1 part tobacco

1 part compost

1 part rock dust

1 part organic tree fertilizer 

1 part microbes 

Mix this combination well and place approximately one pound in each vent, to be replaced every six months. This mixture will not only kill any pests attacking the tree but will also act as a preventative measure.

• Garlic — One part garlic can be added to the above mix to really make it effective, especially if you think your tree is already infested with the beetle. Garlic can also be planted at the base of the tree for control. This will also destroy the fungus on contact.!

• Orange TKO — This is an organic product that will kill the beetle and destroy the fungus on contact. You can make a mixture by adding one part mineral oil and 1 part OTKO. Use straight and paint it onto the areas that show the small hole bored. This should be done once a month as needed.

Some foliar applications that will raise the Brix levels of your trees include compost tea, rock dust tea or microbial sprays like Superseaweed, Nitron A-35 or Agrigro. All of the above will slowly raise the Brix levels of any plant and work best if they’re applied during late spring or early summer. 

Compost tea will also provide a sort of inoculation against most fungus.

Never spray your trees with a chemical fertilizer. There are many excellent organic fertilizers available which also have all the needed microbes

To avoid stressing out the tree, regularly apply rock dust, compost and mulch and avoid over watering.

Email your gardening questions to Andy at andy@invisiblegardener.com and he will answer them in his next column.