We often get questions from growers about reusing wooden or other stakes for tomato and pepper production, particularly if diseases like Phytophthora blight, Pythium root rot or bacterial canker were present where the stakes were used the previous year. The pathogens that cause these and other diseases can survive over the winter in soil and plant debris on stakes. We recommend power-washing or brushing stakes to remove all of the soil and plant sap, followed by disinfecting. This may be a big logistical headache for growers with a lot of stakes. In the Midwest Vegetable Production Guide for Commercial Growers (pages 80-81), we recommend soaking stakes in 10% bleach or quaternary ammonium disinfectants, followed by rinsing and drying.
There is more information on disinfecting stakes in the Mid-Atlantic Commercial Vegetable Recommendations (page 12): “The preferred (and most expensive) method of stake disinfestation is heat treatment. Pathogens are completely eliminated from wooden stakes with exposure to ≥ 220°F for ≥ 15 minutes. This can be accomplished in a large capacity autoclave, or seed dryer. It is unlikely that most growers will have access to such equipment. Alternatively, therefore, stakes may be exposed to disinfectants such as commercial chlorine solutions (sodium hypochlorite) or Oxidate® (hydrogen dioxide; see below). Research has shown that a 20-minute soak in a solution made of 5 to 20 parts by volume sodium hypochlorite (commercial bleach) to 80 to 95 parts by volume water is effective in eliminating pathogens only from the surface of wooden stakes. It is crucial to maintain the pH of the bleach solution within the 6.0 to 6.5 range, as effectiveness decreases at lower and higher pH levels.”
“Studies on stakes treated with bleach solutions show that pathogens may still be present beneath the surface at depths ≥ 1/16th inch. Pathogens embedded within the stake may be able to migrate back to the surface and re-infest plants, although this has not yet been demonstrated. To improve the effectiveness of procedures for removing microbial pathogens from stakes, consider the following: Add a non-ionic surfactant to the disinfesting solution; increase the soaking time to ≥ 1 h; apply a vacuum during the stake soak; use a higher concentration or more potent source of hypochlorite (such as “heavy duty” or swimming pool grade chlorine); or use stakes comprised of nonabsorbent stake materials (such as plastic or metal). Many growers have successfully used the commercial product Oxidate® or chlorine dioxide to disinfest stakes. Oxidate® is OMRI certified and had been demonstrated to be an effective control agent for several important plant pathogens. However, data on the efficacy of this treatment as compared to using heat or commercial chlorine solutions are not available.”
All disinfectants are quickly inactivated by organic matter, so getting as much of the soil off the stakes as possible before sanitizing would improve the results.