May 23, 2015

1 - Lead coated fencing wire should pose little threat to garden plants, but galvanize wire is better.

Yard and Garden May 23, 2015

Q.

I have a question today related to rabbit wire or 1/2" by 1/2" wire. We use this to keep squirrels, snakes and birds, etc. out of our garden.

While installing this wire I noticed that it is coated with lead. In the past we have used bird netting which worked well but over time breaks down and holes appear, thus letting these pests rob us of our vegetables. The question is, does the lead (toxic material) pose a problem over time breaking down then leaching into the soil? Also will the plants absorb the metal and translocate them to the edible parts of the plant? We grow mostly tomatoes, chiles, and a few types of lettuces.

A.

Are you sure the wire mesh is coated with lead? Most of fencing materials such as what you have described are galvanized - coated with zinc. Lead is indeed toxic if you ingest it in sufficient quantities. Lead paint was banned from household paints many years ago and more recently from paint used for toys and furniture. The problem was mostly from direct ingestion of paint chips or children chewing on painted surfaces. Elemental lead (metallic lead) used to coat wire would be very insoluble in water at pH (acidity / alkalinity) levels common in the garden environment. In this form it has a high affinity for soil particles and will bind to the soil and will not be easily absorbed by plant roots. Since minerals must be dissolved in water to be absorbed by plants, the chances for entering the plants and creating toxicity problems are minimal. Even plant leaves (lettuce) that come into direct contact with elemental lead will probably not absorb the lead, but there would be a very small chance that it could be adsorbed on the leaf surface. Keep lettuce plants and whatever will be eaten from directly contacting the wire, if it is coated with lead.

Check your fencing material again to be sure it is indeed lead that has been used to coat it. It is more likely to be coated with zinc. Zinc is a plant micronutrient, meaning that plants need small quantities of it so you ingest zinc when you eat plant materials all the time. In high concentrations it can be toxic, but that is again very unlikely. Many people actually take zinc dietary supplements. Zinc is also relatively insoluble in water at pH levels common in the garden. We must sometimes treat soil or plants with zinc to overcome deficiencies in the plants.

If the wire proves to be coated with lead you may want to purchase galvanized fencing material. You can tell the difference because lead is quite soft and easily scratched from the surface of the wire. Zinc is much harder and will require steel or some hard material to scratch it from the wire.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

Links:

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