Tips to Be Prepared for Fire Blight

The battle against fire blight can sometimes seem like a never-ending process. According to Washington State University Extension agent Tim Smith, simply taking advice on how to control fire blight does not always work. “Fire blight infection risk evolves much faster than most other pests,” notes Smith. “Advisers can warn you that a high blight risk period is coming, but day-to-day decisions during the time that risk is high are up to you.”

Fortunately, Smith offers a number of important steps that growers can take to minimize both the risk and the damage from fire blight. While it ultimately comes down to personal choice, these strategies can serve as a guide.

– Sanitize. Preparing for fire blight is a year-round process. Cut blight out of your orchard as much as possible during the winter. Cut before you prune, so you may remove the blighted cuttings from the orchard. Once summer hits, cut blight as soon as you see it.

– Manage your orchard environment. For example, the amount of dew in your orchard can determine the risk of infection. If blossoms are present and the weather has been warm, the light wetting that may occur from sprinkler mist can trigger blight. Soil drying can be beneficial, assuming the trees are well watered when the really stressful time of year starts.

– Reduce infection potential of the host. One way to do this in a young block is by hand-removing blossoms. The labor on this is not as bad as it seems. In fact, if a fire blight model says your risk is high, and your young trees have scattered blossoms, pulling the blossoms may save you more than the cost of labor. On larger trees, any caustic blossom thinning sprays that burn off the stigma tips are likely to prevent the continued build-up of the blight bacteria on the treated blossoms. Of course, an obvious step is to plant on fire blight-resistant rootstocks.

– Watch your models. This is where it can get tricky. Controlling this disease is difficult unless you apply an effective control product very close to the infection time. Whenever blossoms are wetted during a time that your model indicates your orchard is in high or extreme risk, infection is likely in your region, but not necessarily in your orchard. The decision on whether to make a treatment application is up to you, but the economic and emotional punishment for being wrong about this decision is far greater than the expense of a properly timed, justified spray.

There are models to help you make this decision. One of the most popular is CougarBlight, available at www.ncw.wsu.edu/tfindex.htm. Refer to the site for specific use instructions.

– Apply preventative sprays when necessary. While a model clearly shows the degree of potential risk of infection caused by temperatures, it cannot predict exact blossom wetting. If the risk is low to moderate, you can relax, or at least keep an eye on the weather forecast. If the risk level gets higher, and you believe blossom wetting in the next 24 hours is a possibility, you may want to apply a pre-emptive preventive spray. Either way, it’s hard to make the wrong choice. If rain does take place, and you haven’t applied anything, you can still spray a recommended rate of an effective antibiotic to wet the interior of all blossoms.

– Scout for and remove strikes. If you have identified a likely infection period, begin scouting the orchard about five to seven days after infection. Symptoms usually show up within this period.

Prevention of infection is a far better approach to controlling fire blight damage than cutting wood (see this article’s Bonus Web Coverage). In fact, the best approach is to work within your own acceptance level.