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Organic Gardening: On the front lines of natural pest control

Brian Allnutt
Special to The Detroit News
Hornworms can do a lot of damage to tomatoes.

              Bugs – or the possibility thereof – are often one of the things that new growers worry about the most. But while many backyard growers may be seeing some damage from insects or disease by this point in the year, in most cases garden pests are not a big deal.

              Among other things, organic growers need to appreciate the concept of acceptable losses. Not every chewed leaf or nibbled tomato demands an immediate, chemical response. In fact, many growers believe that some pressure from pests or other stressors help produce more hardy, resilient crops.

              But if you see pests in larger numbers and plants seem to be growing less well than usual, it’s time for action. Organic principles dictate that gardeners always use preventative tactics and physical controls before moving on to any form of spraying or other organic, chemical treatment. This is one reason why organic growers sometimes refer to it as a “knowledge-intensive rather than product-intensive” form of growing. The growers’ own observations and planning are the most important tool in the organic garden.

              In terms of prevention, watering and harvesting at the right times are important for preventing disease. Watering early in the day is best because water left to sit overnight can breed pathogens. Harvest summer fruits like tomatoes, peppers eggplants, squash and cucumbers in the afternoon after the dew has dried. This limits the spreading of pathogens–like powdery mildew–from plant to plant. If you have multiple plantings of cucumbers, pick the youngest first to avoid transmitting diseases from the older ones.

              For insects, physical controls are often the first and best line of defense. Generally, I use no pesticides in my home garden and keep bugs in check with two simple methods: “water-blasting” and “hand-squishing”. These are both rather self-explanatory, but water can used to knock aphids off plants and they usually won’t find their way back on. A quarter turn valve on the end of a hose can be especially useful for this, open it slightly to produce an intense spray of water and simply blast the aphids off.

              “Hand-squishing” is not for the squeamish. Yet, it’s much better for the overall ecosystem than spraying even organic pesticides, which can kill beneficial insects. I’ve used this to control slugs, cabbage worms and tomato hornworms. It also works for Colorado potato beetles, although I’ve found the best technique is to put a bit of soapy water in the bottom of a five-gallon bucket and shake the potato vines over it to dislodge the bugs. This isn’t perfect, but it works well enough to keep the population in check.

              If aphids get really out of control, use Safer soap as a first line of defense. Occasionally, I’ve had to use neem-oil–which is slightly stronger than safer soap–on the grey aphids that feed on kale, cabbage and Brussels sprouts, especially in fall.

              Bt–a bacteria that feeds on caterpillars–can be used for cabbage worms and tomato horn worms, but I’ve never had to use this in a non-commercial setting where hand control seems to work just fine.

              If snails or slugs are causing a major problem in the vegetable or perennial garden, the organic product Sluggo deals with them well. I have never had any luck using beer for this and consider it a waste of an otherwise noble liquid.

              Powdery mildew and the more serious downy mildew can be problems for squash and other plants. However, most squash will get powdery mildew at some point in the season and succeed in producing a crop in spite of it. Neem offers some measure of control against these diseases, but perhaps the best way to keep fungal diseases in check on squash, tomatoes or other plants is Actinovate. This is a biologically active fungicide that colonizes leaf surface to prevent pathogens from spreading and it has become an important tool for organic growers.

              All the products discussed here are organic. When shopping, look for the OMRI label that indicates a pesticide is acceptable for organic use. It’s also–of course–very important to know that you are spraying for the right thing. The beauty of organic controls is that they’re much more pest-specific than their conventional counterparts, so they do less damage to the broader ecosystem. However, this also means it’s very important to use the correct product. Cornell’s entomology department has a great online resource to help you make the right identification: http://idl.entomology.cornell.edu/factsheets/#Vegetables. Samples of diseased, vegetable material can be sent to Michigan State University Extension for diagnosis.

You can reach freelance writer at Brian Allnutt at brian.allnutt@gmail.com.