The Challenge of Disease Control in Organic Crops

December 03, 2010

People buy organic for many reasons. find out why?

People buy organic for many reasons. A recent Lempert Report quick poll found that 62% of consumers associate organics with being hormone free, made with no artificial flavors and color and grown with no pesticides. Many will buy organics, despite the cost, in order to purchase what they perceive to be a kinder, gentler, healthier product – both for their bodies and for the planet. However, the business of raising organic crops is one filled with many challenges, not the least of which has to do with providing disease control under government approved organic standards. 

Although organic farmers do not have the large selection of insecticides that are used in conventional agriculture, they do have some to choose from. Approved methods run the gamut. For example, to control spider mites, an organic farmer might use finely ground dusting sulfur, or, to control worms and thrips, an organic farmer might use spinosad, which is an insecticide derived from a naturally occurring, soil dwelling bacterium. 

For more complicated pests, like lepodoptria (moths, butterflies), there are many bacillus thuringiensis insecticides available. Aphids are treated with the natural form of pyrethroid insectide, called pyrethum, derived from the chrysanthemum family of plants. And to disrupt the mating cycle of for other insects that attract crops, pheromones are applied.

Fungus provides a particular challenge, because there are few fungicides available that are approved for organic farming in this area. Sulfur dust is used to control powdery mildew, and various forms of copper can be sprayed for control of bacterial spec, blight, or other diseases. For weed control, many organic farmers use propane fueled burners. Interestingly, organic farming has an exemption in using labor to hand weed in organic fields. This means that laborers are allowed to spend the day on their hands and knees for some crops removing weeds from organic fields – a practice that is not allowed in conventional crops. 

Don Cameron, 58, grows organic tomatoes, as well a large variety of other organic and conventional crops, on his 5,500-acre Terranova Ranch in Helm, California. Farming since 1981, Cameron started growing organic tomatoes in 1993. His efforts in the field have contributed greatly to the expanding organic market. Cameron says that, in many cases, organic farms employ fewer disease control measures than on conventional farms, and that an organic grower may benefit from a conventional neighbor’s spray or insect control measure as it keeps down the pressure, insect or disease for the organic field.

“Conversely, an organic grower’s field may become infested with an insect, disease, or weed problem that may easily spread to a conventionally grown field nearby. Mildew spores can be spread by wind from an organic vineyard to neighboring conventional vineyards, causing the conventional farmer to increase his fungicide applications to prevent disease outbreaks from increased pressure. Insect infestations can move quickly from organic fields to neighboring fields, thus increasing the use of insecticides on these fields,” he says.

Yet another challenge is insecticide resistance, says Cameron. For many crops that Cameron grows organically, losing a key insecticide could mean either incurring a greater loss of his crop, or abandoning a susceptible crop from his crop rotation. In fact, in his organic walnut orchard that is 10 years old – and has been producing walnuts organically for five years – the scale insect has become prevalent. Cameron is going to have to convert the trees back to conventional production to gain control of the insect before the trees are permanently damaged. This means that the orchard will no longer be certified organic.

“This is the only choice I have, or lose an investment in the trees that took five years just to get into production and has a life of at least 25 years,” says Cameron. “Many times there are no choices left as an organic grower. This is why we only have 10% of our farm certified as organic. The risk is too great to do more.”

Cameron says he is a strong proponent of biotech crops being allowed in organic production for this very reason. First of all, the advantageous presence of minute amounts of a GMO trait in an organic field does not disqualify the organic crop from being organic. Secondly, the same bacillus thuringiensis genes that help fight lepodoptria are implanted into Biotech crops, and yet organic farmers are not allowed to use bacillus thuringiensis if it is within the plant itself. Cameron says there is no logic for this type of reasoning. Also, he points out that with the advent of genetically modified drought resistant crops, organic production with non-biotech crops is becoming even more unsustainable. 

“Most organic crops yield less than conventional and biotech now; with the introduction of drought resistant traits, not only will the biotech crop produce more on the same acre of land, but it will now be using less water to produce more. This speaks to the heart of sustainability. The decision not to adopt this technology in organics was not based on sound science, but rather on emotion, and will, in the future, cripple the organic industry when looking at true sustainable metrics,” Cameron adds.  

The National Organics Program defines the organic system as the way in which agricultural products are grown, harvested and processed, and products bearing the organic label must be made without the use of toxic, and persistent pesticides and synthetic nitrogen based fertilizers, antibiotics, synthetic hormones, genetic engineering, sewage sludge, or irradiation. As such, organics are the part of the most heavily regulated and closely monitored production system in the U.S.

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