Extension Utah State University

Applying Organic Pest Management Techniques in the Garden

By Nick Volesky, USU Extension

Organic is a broad term that refers to or derives from living matter. In chemistry, it denotes compounds containing carbon. In agriculture and horticulture, organic relates to production practices that avoid the use of artificial agents in soil media, composts, seeds, plants, fertilizers, or pesticides. Gardeners who apply organic practices do so for a variety of reasons, including concerns for personal health, preservation of their local environment, along with promoting biodiversity. When it comes to dealing with insect, arthropod, or plant disease problems in vegetable gardens, many organic gardeners will turn to the integrated pest management concept. This is both a sustainable and evidence-based approach to managing pests by combining biological, cultural, physical, and chemical tools in a way that minimizes economic, health, and environmental risks.

Biological pest control harnesses the adverse effects of one living organism on another, which may include predation, parasitism, or pathogen infection of pest populations. While gardeners often rely on well-known beneficial insects such as lady beetles, lacewings, or mantids for pest control, there are many other lesser-known allies in our gardens. These include very small parasitic wasps, predatory mites and beetles, true bugs, nematodes, and more. Beneficial insects can be purchased and released through garden centers and online retailers, offering immediate but sometimes short-lived control due to competition and diminished prey populations. Gardeners can encourage their own beneficial insect populations by providing suitable habitats. Planting flowers and grasses, especially native species, can offer supplemental food and nesting options. For specific recommendations, reference resources such as the Xerces Society’s "Habitat Planning for Beneficial Insects" guidebook.

Cultural pest control utilizes production practices in the garden over a longer period to mitigate pest pressure. Gardeners often implement techniques that already serve this purpose. For example, following proper plant spacing recommendations is crucial not only for a plant’s growth and development, but also for mitigating disease pressure by increasing canopy airflow, thus preventing the spread of foliar fungal or bacterial pathogens (i.e. blights and leaf spots). Using drip irrigation instead of overhead watering can reduce canopy humidity which is optimal for plant pathogen development (i.e. powdery mildew). Working the soil, whether through tillage or turning, can disrupt any overwintering life stage of insects, such as pupae. The timing of planting can also have an impact; planting later or earlier can prevent overlap with peak pest pressure. At the end of a season, removing plant residue or debris eliminates overwintering habitats for some insects or fungal spore structures. Applying appropriate cultural pest control techniques requires an understanding of the identification and biology of different arthropods and plant diseases.

Physical pest control involves various mechanisms that can immediately stop or prevent pests. One of the most effective methods is physical exclusion, such as applying row covers over desired plants. Row covers can be purchased in varying sizes or grades from garden centers or online retailers. In early spring, they can serve as a method of frost protection, while thinner grades can function as pest control in warmer months. Row covers are available as woven spunbond polyester or mesh netting. Sometimes, specific fruits or flowers can be protected by a single organza bag. When using row covers, ensure they are applied early in the season before adult life stages can access the plant and lay eggs. Also, ensure that appropriate-sized support structures (such as hoops) are used to support the weight of the cover and the continued growth of the plant. For some plant species, like cucurbits, row covers should be removed to allow pollination.

For chemical control, there are multiple pesticide options available for organic gardening, including fungicides and insecticides. These products use primary active ingredients derived from plants, minerals, bacteria, fungi, or other natural sources. Popular products, for example, often utilize neem oil or insecticidal soaps, which can effectively target soft-bodied insects (aphids and thrips). Products containing the bacteria Bacillus thuringiensis are effective on young caterpillar stages. It is important to note that despite being organic and marketed as “safer”, these products are not inherently less risky than synthetic-based insect products. Harm to the user, plants, or other non-target insects can still occur if the product label is not followed or if the product is misapplied.

For gardeners interested in learning more about integrated pest management and organic production techniques, they can find valuable resources and information on the USU Extension Plant Health website. For specific questions and recommendations please reach out to Nick Volesky (USU Extension Integrated Pest Management program).