Apples may seem like the last bastion of pesticide-dependent gardening. In many commercial orchards, apples are sprayed 10 to 20 times per year. It's not hard to find organic home gardeners who still believe it's nearly impossible to grow good fruit without pesticides. Furthermore, most people probably expect organic fruit to come with a few spots or chew marks. I used to rely on insect traps and biological sprays, and I would still have fruit that was covered with disease and infested with worms. Then I found a way to grow pristine apples without using any kind of spray.
Successful organic fruit-growing starts with selecting varieties that are inherently disease resistant. This important first step eliminates half the problem.
The major apple diseases are apple scab, powdery mildew, and fire blight. Of these, only apple scab really affects the fruit. More than 50 years ago, Purdue University, Rutgers University, and the University of Illinois established a cooperative breeding program. Since then, at least 53 scab-resistant apples have been released.
Selecting apple varieties
Of course, just being disease resistant is not enough. An apple must also taste good. As far as I am concerned, many of the recent introductions lack flavor. Two new varieties I like are 'Liberty' and 'Enterprise'. Luckily, you're not limited to recent introductions. Nature has produced plenty of heirloom apples that have excellent flavor, as well as good pie, sauce, and drying qualities. Among them are literally hundreds of disease-resistant apples to choose from.
How rootstock selection affects tree size, years to fruiting, and sturdiness
Just as important as selecting disease-resistant varieties is rootstock selection. I recommend a tree no taller than you can reach. But don't expect anything labeled "dwarf" to be small enough. To the fruit tree industry, that term means anything from 4 to 16 feet. You will know how big you can expect your tree to get only if you know the name of the rootstock.
The most dwarfing rootstocks are M27 and P16, yielding trees of 4 to 7 feet. Next are P22, Bud 146, and Bud 491, which produce trees 5 to 10 feet tall. Bud 9 and M9 create trees 6 to 12 feet tall. The largest I recommend are 8- to 16-foot trees, which you'll get with P2, O3, and the virus-resistant M9 EMLA. In addition to the rootstock, the vigor of the apple variety and soil fertility also affect the size of the tree.
Generally the more dwarfing the rootstock, the sooner the tree will fruit (often two to three years from planting) and the larger the fruit will be. Rootstocks also help adapt an apple tree to climate and soil conditions.
The root systems of dwarfing rootstocks are relatively small or they are brittle. Either way, they cannot adequately anchor the tree, nor do they have access to moisture deep in the ground. Therefore, all dwarf trees must be staked and regularly irrigated.
Thinning increases the size of the remaining fruitThin apples within 35 to 40 days of fruit set. The sooner you do it, the better the results. All things being equal, fruit size should increase, along with next year's bloom potential.
Why so early? Once the apple blossom has been pollinated, the fruit begins to form the seed. The endosperm in the developing seed starts producing the plant hormone gibberellic acid, which promotes enlargement of the fruit. But gibberellic acid also inhibits the development of next year's flower buds, so the more seeds produced, the more gibberellic acid and the fewer flowers and fruit next year. Many apples tend to bear heavily every other year, with little to no fruiting in between. Thinning shortly after blossoms fall helps reduce this tendency and results in more even harvests every year.
I thin to the biggest fruit, leaving one about every 6 inches. In every cluster of apple blossoms, there's one in the center that's slightly bigger and slightly earlier than the others. Orchardists call this flower the king blossom. Because it opens a day or two before the others, the king blossom usually gets pollinated first and therefore produces the largest fruit. However, if the largest fruit is blemished, remove it and choose another. If there's no appreciable difference in size among the fruits, select the one with the thickest stem.
Successful organic fruit-growing starts with selecting varieties that are inherently disease resistant. This important first step eliminates half the problem.
The major apple diseases are apple scab, powdery mildew, and fire blight. Of these, only apple scab really affects the fruit. More than 50 years ago, Purdue University, Rutgers University, and the University of Illinois established a cooperative breeding program. Since then, at least 53 scab-resistant apples have been released.
Selecting apple varieties
Of course, just being disease resistant is not enough. An apple must also taste good. As far as I am concerned, many of the recent introductions lack flavor. Two new varieties I like are 'Liberty' and 'Enterprise'. Luckily, you're not limited to recent introductions. Nature has produced plenty of heirloom apples that have excellent flavor, as well as good pie, sauce, and drying qualities. Among them are literally hundreds of disease-resistant apples to choose from.
How rootstock selection affects tree size, years to fruiting, and sturdiness
Just as important as selecting disease-resistant varieties is rootstock selection. I recommend a tree no taller than you can reach. But don't expect anything labeled "dwarf" to be small enough. To the fruit tree industry, that term means anything from 4 to 16 feet. You will know how big you can expect your tree to get only if you know the name of the rootstock.
The most dwarfing rootstocks are M27 and P16, yielding trees of 4 to 7 feet. Next are P22, Bud 146, and Bud 491, which produce trees 5 to 10 feet tall. Bud 9 and M9 create trees 6 to 12 feet tall. The largest I recommend are 8- to 16-foot trees, which you'll get with P2, O3, and the virus-resistant M9 EMLA. In addition to the rootstock, the vigor of the apple variety and soil fertility also affect the size of the tree.
Generally the more dwarfing the rootstock, the sooner the tree will fruit (often two to three years from planting) and the larger the fruit will be. Rootstocks also help adapt an apple tree to climate and soil conditions.
The root systems of dwarfing rootstocks are relatively small or they are brittle. Either way, they cannot adequately anchor the tree, nor do they have access to moisture deep in the ground. Therefore, all dwarf trees must be staked and regularly irrigated.
Thinning increases the size of the remaining fruitThin apples within 35 to 40 days of fruit set. The sooner you do it, the better the results. All things being equal, fruit size should increase, along with next year's bloom potential.
Why so early? Once the apple blossom has been pollinated, the fruit begins to form the seed. The endosperm in the developing seed starts producing the plant hormone gibberellic acid, which promotes enlargement of the fruit. But gibberellic acid also inhibits the development of next year's flower buds, so the more seeds produced, the more gibberellic acid and the fewer flowers and fruit next year. Many apples tend to bear heavily every other year, with little to no fruiting in between. Thinning shortly after blossoms fall helps reduce this tendency and results in more even harvests every year.
I thin to the biggest fruit, leaving one about every 6 inches. In every cluster of apple blossoms, there's one in the center that's slightly bigger and slightly earlier than the others. Orchardists call this flower the king blossom. Because it opens a day or two before the others, the king blossom usually gets pollinated first and therefore produces the largest fruit. However, if the largest fruit is blemished, remove it and choose another. If there's no appreciable difference in size among the fruits, select the one with the thickest stem.
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| Thin fruit five or six weeks after blossoms drop; the tiny apples will be 3/4 to 1 inch in diameter. |
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| Thin to the largest fruit. If there is no discernible difference, choose the one with the thickest stem. |
Bagging the fruit eliminates the need for sprayed pesticidesEven though there are biological pesticides considered safe for spraying on fruit trees, getting the task done at the right moment can be difficult. Timing is critical. The temperature must be within the correct range, the air must be calm, and you must catch the target insects at the right stage. The window of opportunity is usually narrow and often occurs at inconvenient times -- like when you're at work.
My solution is to enclose the fruit in brown paper bags to keep insect pests from getting at them. Not only is this technique more environmentally friendly than spraying (even with an organic pesticide), but it also gives surer results. Bagging results in fruit that is 100 percent pest free. And if you get the bags on before diseases show up, you can exclude those problems, too.
I like to bag the fruit when it's 3/4 to 1 inch in diameter, usually 35 to 40 days after the blossoms drop. This is a convenient time because I'm already working my trees then, thinning the clusters to a single fruit (see Thinning apples). To be effective, bagging must be accomplished before the pests arrive to infest your fruit. You can use traps to let you know when the pests begin showing up, then hustle. There are pheromone traps for most of the universal apple pests -- codling moth, apple maggot, and leaf rollers.
The materials needed are plain old #4 brown paper lunch bags, a stapler, and a good supply of staples (I use four or five per bag). To prepare the bags, I staple the top together in four places -- just to either side of the little thumb cutout in the middle and also at either corner. If your apples are on the large size, it may help to cut a slit down the middle of each side, about 1 inch down from the top. Outdoors, slip a bag over the little apple and stem, slide the bag so the stem is snug up against one of the central staples, and put in a final staple close to the center so the bag won't fall off. Be careful not to damage the apple or the stem.
Once you get the hang of it, you can bag three or four apples a minute. About a hundred fruits is a reasonable number to let develop on a mature dwarf tree. Remove all unbagged apples to prevent pest populations from increasing. That's all you need to do. Your fruit is now fully protected from both diseases and insects.
As harvest time approaches, I begin checking on the apples. If the variety is one that reddens even slightly when ripe, the bags do interfere with the fruit achieving its full color, so I remove them about two weeks before harvest. If the fruit is one that is fully green when ripe, I leave the bags on until harvest.
Occasionally bags fall off due to rain and wind. When that happens, I simply go out and put on another bag. If any bagged fruit falls, I pick it up right away and compost it, bag and all, so it doesn't become a magnet for diseases and insects.
The only potential insect problem on bagged apples is earwigs. Earwigs are omnivores; they feed on aphids and other small insects, plus plant materials. If earwigs take up residence in the apple bags, they may eat a bit of the apple. The way to counter that is to give them a better place to live. The easy solution is to stuff a clay flowerpot with straw and hang it in the tree. The nocturnal earwigs will go into the flowerpot to hide during the day. Gently pull the straw to see if you have any captive earwigs and move them to a location where you need aphid control.
Tips for keeping your apple trees healthy and productiveJust as a healthy human baby usually grows into a healthy adult, so it is for plants. I maintain good soil fertility and adequate soil moisture levels by keeping the trees permanently mulched. All plant health starts with the soil. Since apples, like most fruit trees, require mycorrhizal fungi in, on, or around their roots, I aim for a soil that has a lot more fungi than bacteria in it. You can enhance fungus dominance by adding brown organic matter, such as leaf mold, sawdust, and woody materials, to the soil.
The spores of apple scab live on fallen leaves and reproduce during the winter. To minimize the opportunities for scab, I rake up and remove leaves as soon as they've all fallen.
I also try to increase insect predators on my trees by planting a ground cover specially designed to attract beneficial insects. You can achieve a similar effect by scattering plants within your garden or orchard. Select plants for a succession of blooms from spring through fall and include ones of different heights. Low-growing plants offer ground beetles a place to hide and lacewings a place to lay eggs. Taller plants provide nectar and pollen for hover flies and predatory wasps.
Before I started bagging, I relied on biological sprays and insect traps, but I still had fruit covered with disease and infested with worms. Now I harvest gorgeous fruit that is safe to eat and is produced in an environmentally sound manner. In other words, fruit I simply cannot buy.
by Ted L. Swensen
this first appeared in Prevent Disease
