Termite insecticides can spoil products

Q: We are concerned about what will happen to some plants if our home is treated for underground termites. The imidacloprid insecticide is applied in a 6 inch deep trench around the foundation. We garden organically and grow vegetables, herbs and fruit trees in a raised bed next to the house. Can we safely harvest these plants after treatment?

A: The insecticide label tells you if the product is registered for use in food crops. Ask the pest control company you hire to give you a copy of the label for the product they are using and the product’s Material Safety Data Sheet (MSDS). You should not harvest products from plants growing near treated soil unless listed on the product label. If your plants aren’t listed on the label, the manufacturer may be able to tell you when they can be harvested. If not, you can relocate the plants before the insecticide is applied.

Bayer Advanced Fruit, Citrus and Vegetable Insect Control, and some other products that contain the insecticide imidacloprid are approved for use on some food crops. Other products containing imidacloprid used to control underground termites are likely not. They may contain a higher concentration of the insecticide, stay in the soil longer, or may not have been tested on food crops.

Organic gardeners do not use imidacloprid. It has systemic activity and is usually applied to the floor. Roots absorb the insecticide and it can remain in plants for several months or more. Imidacloprid fights multiple plant pests, but is also poisonous to honeybees and other beneficial insects that extract nectar and pollen from the flowers of treated plants. For this reason, I do not recommend using Imidacloprid when other options are available.

Q: I am interested in planting a couple of deciduous fruit trees. Do you know how many chill hours the Clairemont area gets?

A: The temperature data required to calculate the winter cold was only recorded at a few locations in the district. Over the 2006-2013 period, the total number of cooling hours (32-45 degrees F) between November 1 and late February ranged from a low of just 3 hours (2009) to a high of 98 hours (2012) at The Torrey Pines Golf Course is right on the sea. Not far inland on the Marine Corps Golf Course at Miramar Base, the total cooling time over the same period was 124 to 482 hours. Further inland at Escondido in the San Pasqual Valley (near the valley floor) the cooling time ranged from 510 to 872 hours.

A table of cooling times per year can be found at www.sdedible.org (click on the “More” tab). The amount of cooling varies greatly depending on the location and from year to year. Winter temperatures are colder as you travel inland from the coast and into canyons and valleys as cold air flows downhill like water.

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