Organic Gardening, Part 3: Weed, Insect, and Disease Management Practices
The last two articles have focused on some basics of what organic gardening is and on soil fertility. This one addresses weed, insect, and disease management.
The law that governs certified organic production in the US requires that people use a comprehensive set of practices, including crop rotation, appropriate nutrient management, and good sanitation practices to manage weeds, insects, diseases, and other pests. People must choose appropriate crops and varieties for the location, including ones with resistance to common problems. Beyond this, the law goes on to specify some practices that can be used specifically for managing weeds, insects, and diseases, and other types of pests. Some likely to be applicable in home gardens include using natural mulches (or synthetic ones, if they can be removed completely after harvest), mowing, cultivating, hand-weeding, maintaining habitats for beneficial insects, and using practices that reduce the spread of pathogens.
A focus on good cultural practices and prevention for weed, insect, and disease management should be shared by all gardeners, regardless of whether they care to be “organic” or not.
Crop rotation is one of the simplest, most effective, and most underutilized ways to reduce disease problems caused by pathogens that survive in the soil and on plant debris. Rotating means moving where you plant certain types of vegetables and other plants. Since plants that are more closely related to each other are more likely to be susceptible to the same diseases, it’s often suggested to rotate by plant family. However, oftentimes, a pathogen affects plants in more than one family or only affects certain plants in a given family, so if you’re dealing with a problem, it’s helpful to know what it is and what the plant host range is so that you can rotate more effectively.
Cover crops, which were discussed in the last article, can be part of crop rotation.
You may wonder why nutrient management is mentioned in the context of pest management. Like humans, when plants are healthier overall, they are generally less susceptible to disease. It’s important for plants to have adequate but not excessive nutrients. In some cases, excessively high nutrient levels can predispose plants to disease or insect problems.
Sanitation practices include things like cleaning equipment and tools after using them in weedy areas or ones with soilborne pathogens, working in diseased areas last so that you don’t spread pathogens on hands or clothing, and getting rid of heavily diseased or insect-infested plants.
An easy way to reduce the risk for disease problems is to water in ways that deliver it directly to the soil, such as by using drip irrigation or directing water to the ground when hand-watering. If you don’t have a practical alternative to using a sprinkler, try to water early in the day so that water evaporates more quickly from plant surfaces. Many pathogens spread in droplets of water, and longer periods of wetness increase the chance of infection by most types of plant pathogens.
What species and varieties are appropriate for an area depends on a number of factors, including the local climate and common disease and insect problems. Genetic resistance is most widely available to certain diseases. When a variety has resistance to a disease of that crop, Extension materials and seed catalogs often note this.
Organic regulations prohibit using genetically modified organisms (GMOs). This does limit the use of disease- and insect-resistant varieties to some extent, but few vegetable or fruit varieties that we would grow here in the southeastern US are transgenic, anyway. Some exceptions include sweet corn varieties with one or more Bt (Bacillus thuringiensis) genes for resistance to stem-boring caterpillars and/or tolerance to glyphosate (“Roundup Ready” varieties), as well as a small number of summer squash varieties genetically modified for virus resistance.
There is a lot of biological control that goes on in nature in the absence of insecticides. There are situations – largely when growing plants in greenhouses – in which it makes sense to purchase beneficial insects or mites, but oftentimes what makes the most sense in a home garden is just avoiding killing the beneficials that are already present.
When practices such as those mentioned above have not been effective enough, the law allows use of “a biological or botanical substance” (with a few exceptions) and certain synthetic substances for weed, insect, and disease management. The next and final article in this series will discuss some of these products.
Let me know if you have questions.
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Dr. Mary Helen Ferguson is an Extension Agent with the LSU AgCenter, with horticulture responsibilities in Washington and Tangipahoa Parishes. Contact Mary Helen at mhferguson@agcenter.lsu.edu or 985-277-1850 (Hammond) or 985-839-7855 (Franklinton).
The Tangipahoa Parish Sheriff’s Office (TPSO), in partnership with the Livingston Parish Sheriff’s Office (LPSO) has arrested a wanted suspect following a high-speed pursuit through two parishes.
