An Example of the Balanced Organic Systems Approach from Spring in the Apple Orchard

How BOSA works on Fire Blight during Apple Bloom

Bloom in an apple orchard is so beautiful. Apple blossom fragrance permeates the air. The breeze becomes warm. As I walk, I am surrounded by sunshine. There are pink buds and white flowers covering all the branches and the trees. As I walk farther, I hear the honey bees steadily visiting flowers, moving quickly from one to the next. If I look more closely, I also see the native pollinating insects that come in so many shapes and sizes: huge bumble bees, metallic native orchard bees, and some pollinators so small they are hard to see. All are busy, all taking advantage of the bloom and flowers everywhere. The yellow dandelions add beauty to the scene even though they compete with the apple flowers for pollinators. It makes my heart glad to see and remember all the preparation that took place over the last year. Since the orchard was first planned and planted we’ve worked to get to this one moment: bloom. I anticipate a good fruit set and the potential for a good crop. Fruit growers expect that every spring at every bloom. It all comes together.

Although I can enjoy this moment, I must remember that it is not a time to sit back and relax. I turn my attention to what may yet be in store for my orchard in bloom. Although there are a few insect pests and diseases I must give my attention to during this season, I’ll focus on just one for this story: fire blight. This bacterial disease is ever present, waiting for the right conditions during bloom to infect flowers, potentially killing branches and even trees as it spreads. I am confident in my organic fire blight suppression approach. Like every aspect of my approach to growing organic fruit I have prepared for this moment from day one. And yet again, for one more season, my confidence and approach to organic fruit growing will be put to the test with the fruit crop, and the orchard itself, at stake.

BOSA Component: Weather

Today is a good pollination day, sunny and nearly 70° F. But the weather forecast predicts a warm rain tomorrow afternoon. I know conditions are building for high fire blight infection risk in my orchard. All fire blight needs to get started is temperatures above 65° F, rain, and open flowers. Even though I didn’t see much fire blight infection in my apple orchards the previous growing season, I know it can overwinter in wood cankers. I focused on pruning out all potential cankers I found while pruning last winter. But I also know one or two missed cankers can cause a serious epidemic. When I get a warm rain tomorrow afternoon, I know I’ll have the three necessary conditions for fire blight infection in my orchard: open flowers, warm and wet weather, and the fire blight bacteria from old wood cankers that I may have missed during pruning.

BOSA Component: Fruit Variety Selection

Although all apple varieties are susceptible to fire blight blossom infection, in some varieties the disease spreads in the shoot and wood more quickly. Crimson Crisp and Crimson Topaz are more susceptible to spread and I saw some fire blight in these trees during the last growing season. I marked the area where I first found evidence so that I could keep a very close eye on the same trees for this bloom period.

I also planted my apple trees on rootstocks that do not produce excessive, vigorous growth. This will contribute to my fire blight suppression strategy since the fire blight bacteria spreads most rapidly in vigorously growing new shoots. These rootstocks also do not support spread of the blight into the tree roots thus preventing tree death.

BOSA Component: Fertility

In the spring I was careful to not over fertilize my trees. Two years ago, I used organic compost throughout my orchard. I applied the compost in a site specific manner based on soil nutrient analysis and based on tree growth observations. Since compost has a long-term impact, releasing its nutrients slowly over four to five years, I know its positive nutrient effects will still be present this season. I put a half rate of nitrogen fertilizer on the orchard in early spring. I will monitor growth both during and shortly after bloom and I will apply fertilizer a second time in late spring only if absolutely necessary; too much growth following bloom encourages disease to spread in the tree. Knowing we had a late spring, I expect temperatures are more likely to be warm during bloom.

BOSA Component: Fruit Rots and Leaf Blights

I sprayed an organic material earlier in the season to suppress the fire blight bacteria already present in wood cankers, which will then prevent it from spreading onto the branches. I have a few organic materials to spray during bloom if I feel infection risk is high. They only provide about 30 to 40% suppression of flower infection but with all my other control tactics it will aid in preventing extensive flower infection.

BOSA Component: Pruning

Every week I’ll slowly go through the orchard looking out for infected shoots which turn brown from the tip. These shoots are often called shepherd’s hooks because they hook at the tip. I will remove the infected shoots and get them out of the orchard to reduce the available fire blight bacteria that may cause new infections. This orchard practice is called sanitation of the disease tissue. I will make sure to mark any fire blight infection spots in the orchard with a colored ribbon for future scouting trips and next year’s winter pruning.

Controlling fire blight in an organic orchard is more intense than the other fruit disease threats I will face, but my organic strategies have worked in the past and they will work again this season. I’ll watch temperatures and rain events closely. Maybe the fire blight risk won’t occur. Maybe it will be nice and cool. But, if there are infection risks, I know I am prepared to protect my orchard as bloom progresses. I’ll sleep easy tonight knowing my balanced, systematic approach will suppress fire blight, one of the most devastating diseases any orchard can face.