Cultural Control

The goal of cultural control is to make the crop environment less suitable for insect pests. Most of the time, cultural control is used as a preventative measure. By anticipating insect problems before they occur, the control techniques avoid or minimize the pest’s impact on the crop. Cultural control techniques are most effective when the target insect pests have few suitable host plants, do not disperse far or frequently, and/or have complex nutritional or environmental requirements during their life cycle.

When using cultural control techniques, it is important to be aware of the environmental context of the field. Production efficiency, yields, soil conservation, natural enemy habitat need to be taken into account for each crop/pest complex, climate, and surrounding environment. This is because cultural control techniques that maximize insect control may at times be impractical in particular contexts. For instance, the practice of tilling to disrupt an underground life stage of an insect pest may not be practical for a no-till farmer trying to reduce erosion on his or her field.

Habitat disruption and sanitation

Field and facility sanitation: Insect pest habitat can include crop residue, spilled seed, weeds along crop edges, volunteer plants, and soil. One technique to reduce or disrupt these habitat is sanitation. Sanitation is important both in the field as well as in storage and processing. Destroying or removing crop residue from the field by plowing, shredding, chopping, burning, or feeding it to livestock can remove or kill insect pests that are inhabiting the residue. This technique can compromise soil conservation, however, as crop residue is a source of soil nutrients and erosion control. Sanitation in storage and processing can be achieved by keeping facilities clean and eliminating spillage. These practices can reduce the spread and population growth of insect pests.

Physical removal: Roguing is the practice of identifying and physically removing infected, infested, or abnormal plants from a crop field. Its primary utility is to reduce the amount of inoculum of insect-vectored plant pathogens such as viruses, phytoplasmas, and bacteria in a field and stop the spread of diseases caused by these agents. Examples include removing potato plants from a seed field that show symptoms of potato virus Y, or removing carrots showing symptoms of Aster Yellows, to prevent subsequent spread by aphid or leafhopper vectors to additional plants in the field.

Tillage: Tillage can reduce some pest populations while attracting others, so it is important to know how your target species responds to tillage and what other pests tillage might put you at risk of attracting. If tillage is timed with a stage of the pest’s life cycle that is underground, it can be used to directly control insect pest populations. For pests that overwinter in the soil, mortality is increased when tillage occurs before a cold winter. The soil disturbance exposes the insect to harsher temperature and soil moisture conditions, reducing the likelihood of survival through the winter.

Non-crop habitat and edge management: Destroying or modifying non-crop pest habitat is another technique to reduce or disrupt pest habitat. In Wisconsin, some insect pests overwinter in plants growing around field edges. Burning or plowing these plants disrupts the habitat for these insects and can reduce the number of pests that overwinter. It is important to note that destroying this field-edge vegetation removes habitat for natural enemies, and so it is recommended to survey these areas for beneficial insects to determine the value of the vegetation.

Spatial and layout modifications

Planting density: Planting densely so that the crop forms a closed canopy reduces the amount of contrast within a field. Some migrating insect pests are attracted to areas of contrast, so reducing contrast will reduce the attractiveness of a field to these insects. Additionally, dense planting increases humidity, creating a less favorable environment for some pests, but may increase the risk of some diseases.

Landscape context and spatial isolation: At the multi-field scale, locating dissimilar crops next to each other can limit pest and disease movement from field to field. Crops ideal for sharing field borders are those that are susceptible to different pests. In potato seed production, spatial isolation is a critical component of potato virus Y management, by reducing the amount of inoculum present in the landscape that aphid vectors can move into a field. In potato pest management, Colorado potato beetles overwinter in field edge habitats and will colonize fields the following year from those habitats. Knowing where previous potato was planted can help direct scouting and early-season pest management.

Intercropping and companion planting: Alternating crop rows or mix-planting non-host or repellent crops can reduce pest discovery and colonization of crops. Intercropping can also have significant nutrient management effects by intercepting nitrogen that would otherwise leach into groundwater resources.

Mulching: Using reflective plastic mulches can disorient flying pests like aphids, thrips, and whiteflies. Mulches can also increase the temperature of the soil, improving early-season plant growth, while reducing soil-borne disease transmission. Organic/straw mulches can also be used to reduce soil erosion and drying while also providing habitat for soil-dwelling natural enemies.

Avoidance in time

Crop rotation and sequencing: Disease and insect lifecycles can be disrupted by rotating to a different crop that is not a suitable host in the following season. Planting the same crop in successive years will often lead to increasing disease and pest pressure and should be avoided if possible. Be sure to rotate to a different plant family because crops in the same family will often be susceptible to the same pests and diseases. For example, tomatoes or peppers should not follow potatoes, because they are all nightshades (family Solanaceae). Crop rotation can also significantly improve soil health and nutrient management.

Planting timing: Adjusting crop planting in time means planting a crop at a time when the likelihood of damage from a key pest is reduced. This can be done by adjusting the date of planting or other field operations around an insect pest’s lifecycle. Planting around a pest’s lifecycle can reduce insect damage by avoidance or tolerance. Planting or harvesting a crop before (or after) a pest is present reduces insect damage by avoidance. Trapping and calculating an insect’s growing degree days can assist with planning around a pest’s lifecycle. Damage tolerance can sometimes be achieved by planting a crop early so that the plants are stronger, more resistant, and more tolerant to damage by the time insect pests are present.

Harvest timing: Risks from some pests, insect-vectored diseases, or adverse weather events can be reduced by harvesting a crop early. In potato seed production, several factors interact at the end of the production season to complicate this choice. Yields can be increased by delaying vine kill, but aphid populations increase significantly towards the end of the season, increasing the risk of potato virus Y transmission and seed lot rejection.

Diversion and attraction

While crops are often suitable hosts for insect pests, they are not always the best host. By creating a small, controlled space that the pests prefer, it is possible to divert pests away from the primary crop. Two techniques for this are trap cropping and strip harvesting.

Trap cropping is planting a preferred host plant of an insect pest near the primary crop that is to be protected. The pest then infests the preferred or “trap” crop instead of the primary crop. If necessary, the pests can then be killed in the trap crop. Trap crops can be any species that the pest prefers—even be the same species as the primary crop. If the trap crop is the same species as the primary crop, it should be planted at a time that will best lure the pest away from the primary crop.

Strip harvesting is the practice of harvesting a crop in sections over time. This practice is useful when harvesting a trap crop because it maintains some habitat for the pest. As a result, the pest does not move to find new habitat in an adjacent higher value or more susceptible crop.

Non-crop habitat management

Buffer strips: Conservation buffer strips are narrow areas of permanent vegetation – such as grasses, wildflowers, shrubs, or trees – planted alongside farm fields, streams, or lakes. They trap pollutants, slow storm water runoff, stop topsoil erosion, and provide safe homes for wildlife and pollinators.

Pollinator plantings: A form of buffer strip, these plantings focus on establishing native perennial wildflowers along field margins as an alternative to tilled or mown grass field margins. Pollinator plantings provide habitat for bees and natural enemies that provide valuable ecosystem services and can improve public perception of agricultural land use.

Beetle banks: A beetle bank is a raised earth ridge planted with perennial bunch grasses running through a crop field. It provides a safe winter home for beneficial predators like ground beetles and spiders, which naturally control pests like aphids and slugs without chemical pesticides

Agronomic practices

Fertility management: Matching fertilizer applications to crop needs prevents runoff and maximizes yields, while keeping plants from becoming stressed and attracting pests.

Cultivar selection: Choosing to plant cultivars that are resistant to pests and diseases can result in better outcomes while saving time and money. Similarly, for vegetatively-propagated crops such as potatoes, select high-quality seed free from diseases and imperfections.

Cultivar-specific management: Some crops and cultivars are more tolerant of insect damage or more resistant to diseases and so can be managed less intensively without incurring yield losses. Review the scouting recommendations and economic injury thresholds for your particular cropping system and pest to determine when further interventions such as chemical sprays are warranted.