Building Health in the Orchard

Fall 2014

By C.J. Walke

Reactive Remedies

My favorite role in my work with MOFGA is helping growers and gardeners troubleshoot insect pest and disease issues in their fruit trees while developing strategies to keep those pests in check to allow fruit to reach harvest. Most often I am approached or contacted once a pest population has exploded or a disease has become widespread, and typically no immediate remedy exists in our organic toolbox. Once the curculio and codling moth larvae are inside the fruitlet, they are safe and sound, and all you can do is pick the affected fruit or gather the drops, but the fruit is lost and you need to start thinking about next season.

The concept of “remedies” seems to permeate our culture, in which we believe we are smart enough to solve any problem, and most often the problem is one we’ve created or allowed to come into existence. Remedy doesn’t work so well in organic farming. A spray tank of Bt or spinosad might knock back a pest population to a manageable level, but the population will rebound because the spray application did nothing to change the environment we created to host these pests. And they will return.

This is where we need to think about being proactive, a word that makes me a bit queasy and one that we often hear from our dentist or primary care provider or spouse, but they are always right. (Yes, dear.) Planning and education are key to knowing what you are getting involved with and what challenges you may create for yourself when you plant 50 fruit trees. This (education and planning) is where MOFGA staff expend tremendous energy for farmers and gardeners so that they have a solid start and know what lies ahead.

Words into Action

Organic farming starts with the soil – the heart of the practice: a healthy, biologically active soil that will hold nutrients and moisture to nurture the crops we are producing. Orchard plantings will have a far better start in a soil that has been amended and cover cropped for the season before trees are planted. This puts nutrients in place, based on soil tests, and knocks back weeds that will compete with the young trees – weeds that will win the battle for space, especially if you are planting dwarfing rootstock. I often receive photos of struggling young trees with poor growth and weak foliage, and I’ll ask about soil testing and for a photo of the ground around the tree. The most common answer is that no soil test was done, and grass is choking out the root system. Start with the soil.

And young trees shouldn’t stand alone in the field; they should have some company, some companions. When I planted 50 new trees this spring, I didn’t just plant the trees, I planted woody shrubs and perennial herbs in various places. The dwarf trees along the garden edge are spaced 8 feet apart and interplanted with sage, chives, oregano, thyme, sweet cicely, yarrow and other herbs that we use in the kitchen that also provide food and shelter for beneficial insects. We also planted flowering shrubs nearby (viburnum, willow, elderberry, Pieris japonica), some planted by an old fence and others around a rock pile – all to support beneficial insects that will offer some protection to the trees, but mostly to diversify the space with numerous crops and build a different aesthetic than straight rows of trees.

As we move into the canopy of the young tree, gentle pruning and limb spreading to establish structure are essential in the early years, since branch angles cannot be changed easily in future years. Just as we cultivate diversity in the soil below, we should think about diversity within the tree canopy. Numerous fungi, bacteria and yeasts colonize in the canopy, occupy space and feed off each other to create a unique food web in trees. Life abounds on the leaf surface, but not to the naked eye, and we need to encourage diversity there as well.

This is where the term “competitive colonization” comes into play. I’ve been working to understand this concept better. Numerous microbes, mostly bacteria, colonize the leaf surfaces of healthy plants, and this microscopic ecosystem is referred to as the phyllosphere. Dozens of species of bacteria can exist on the leaf surface of a healthy apple tree – emphasis on healthy tree – and take up space so that less room is available for a bacterium such as Erwinia (fire blight) to take hold. If there’s limited space on the leaf surface and we can encourage populations of harmless microbes, then the few harmful microbes have less space to get established.

We can encourage the beneficial microbes by applying various food sources to the tree canopy, such as cold-processed fish and neem oil, while also using cultures of effective microbes to regenerate populations. On the other hand, using mineral fungicides (copper and sulfur) to combat harmful microbes will eliminate these beneficials, creating a clean slate and wide open space for fire blight and apple scab to land and take hold. As organic farmers and gardeners, we understand the importance of the microbial activity in our soil, but a whole new world exists on the leaf surface, be it an apple tree or a dry bean. There is far more to learn in the phyllosphere when we view it as a healthy microbial ecosystem and work to strengthen it, rather than waiting for disease to descend and ailments to establish and then falling back into the rut of remedy.

C.J. Walke is MOFGA’s organic orchardist and librarian. You can address your orcharding questions to him at 568-4142 or [email protected].

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