Trap Crops, Intercropping and Companion Planting - University of Tennessee
W235-F TA IN A BLE US Trap Crops, Intercropping and S O R G A NIC & C TIO N Companion Planting DU R O CR OP P Annette Wszelaki, Associate Professor and Commercial Vegetable Extension Specialist Sarah Broughton, Former Graduate Research Assistant Department of Plant Sciences Benefits of trap crops and intercropping: Reduce damage to cash crops Attract beneficial organisms Decrease the use of external inputs (e.g., insecticides, herbicides, fungicides) Enhance biodiversity Increase productivityTrap CropsTrap crops are grown as a control measure to lurepests away from the cash crop to protect it fromattack. Pests are either prevented from reachingthe crop or concentrated in certain parts of thefield away from the main crop. The principle oftrap cropping relies on pest preference for certainplant species, cultivars or a certain stage of cropdevelopment. Plants produce chemicals, or volatiles,that attract insects for pollination and repel pestinsects. Different species and cultivars producevarying degrees of unique volatiles, allowing certainspecies or varieties to repel insect pests more stronglythan others, making them suitable for selection as is limited; therefore, main crops seldom requirea trap crop. The two primary techniques utilized in treatment with insecticides. When insect pests are attrap cropping are: 1) selection of a more preferred high concentrations in trap crops, they can be treatedplant species or cultivar grown at the same time as in a localized area instead of treating the entire field.the main crop; 2) planting of the same species and Savings resulting from reduced pest attack andcultivar as the main crop timed to be at the most insecticide use may substantially outweigh the costpreferred stage of development before the main crop. of maintaining crops that do not provide economicWhether using the same or different species, it is income. Reduced damage to main crops alsoessential that the trap crop be more attractive than the increases their expected marketable yield. Further, amain crop. variety of plantings and increased concentration of insect pests may attract natural enemies, enhancingTrap cropping offers several benefits in a pest naturally occurring biocontrol.management system. When trap crops successfullyattract pest populations, damage to the main crops
The design and arrangement of trap and main crops → Row intercropping refers to two or more cropsdepends largely upon the target pest. Knowledge of grown together at the same time with at leasttarget insect behavior is therefore necessary when one crop planted in rows.creating a field design. For example, a perimeter trap → Strip intercropping refers to growing two orcrop may be sufficient for reducing damage of the more crops together in strips wide enoughmain crop by Colorado potato beetle, but intermittent to permit separate crop production usingplantings may be required for more mobile species machines but close enough for the crops tosuch as the striped cucumber beetle. Trap crops may interact.also be designed for nematodes and fungi that cause → Mixed intercropping has no distinct row orplant diseases. The required size of the trap crop is strip arrangements.a function of the number of pests expected and the → Relay intercropping is used for planting inmobility of the species, but the proportion of the succession, where a second crop is plantedtrap crop is typically 10-20 percent of the main crop. into a standing crop at the reproductive stageThe primary key for effective trap cropping is the before harvesting.successful establishment and management of thetrap crop stand; more desirable plants within the trap Seeding rates are often reduced to avoidcrop stand will have a greater impact on luring pests overcrowding. Rates should also reflect the desiredaway from the main crop. For enhanced control, the yield for each crop. Staggering planting / harvestinguse of trap crops can be combined with other pest dates takes advantage of peak resource demands,management strategies, such as crop rotations, to reducing competition between crops. Including plantsreduce the number of expected pests, and pheromone with a variety of heights and growth patterns alsotraps, to attract pests to desired areas away from the ensures reduced competition. For example, a tall cornmain crop. plant can capture sunlight and create a beneficial understory environment for a low-growing, shade-Despite the benefits of using trap crops, there tolerant species.are several concerns. First, trap cropping is onlybeneficial when fields are likely to be invaded with The use of intercropping can provide benefits tohigh numbers of pests. Improper management of a management system, including decreased insectpests on trap crops may create “pest nurseries,” pest pressure, reduced need for external inputs,facilitating a more rapid or widespread pest outbreak increases in biodiversity, enhanced production andthan may otherwise have occurred. Treatment of lower economic risk. Separating susceptible plantstrap crops with insecticide may lead to increased with non-host species provides a physical barrier toevolution of pesticide resistance and destruction of insect pest movement, limiting spread and decreasingnatural enemies. Further complications may arise likelihood of damage to susceptible varieties. Forwhen trying to manage multiple pests with different example, separating plantings of solanaceous crops,behaviors. Application may be limited for certain such as tomatoes and potatoes, that are susceptible tocrops.IntercroppingIntercropping is the growing of two or more cropsin close proximity to promote beneficial interactionsbetween them. The principle of trap cropping relieson combining plants in such a way that they occupydifferent ecological niches. Plants that occupydifferent niches are more likely to complement eachother as they use different resources and carry outdifferent functions.When designing an intercropping scheme, there arefour components to consider: spatial arrangement,plant density, maturity date and plant architecture.Intercropping may be used in several spatialarrangements:
Colorado potato beetle, with a non-host crop, such ascorn, can reduce the movement of Colorado potatobeetles from one solanaceous crop to another. Theaddition of multiple species enhances biodiversityand encourages beneficial insect populations, offeringnatural biocontrol. Resulting beneficial interactionsbetween plants can confuse insects, lowering insectpest levels, lessening the extent of damage andreducing the need for external inputs. Inclusion ofmultiple crops utilizing different environmentalniches increases the productivity per unit of land,allowing for financial diversification, as well as areduced financial risk in the event of crop failure.Companion PlantingCompanion planting refers to the establishment oftwo or more species in close proximity so that somecultural benefit, such as pest control or increased interact with other organisms. Some plants repelyield, may be achieved. Companion planting is a pests; for example, onions and leeks grown alongsidemethod of mixed intercropping most often used carrots can act as a repellant to the carrot fly. Otherin small gardens; other methods of intercropping, plants attract beneficial insects that help managesuch as row or strip intercropping, are intended for pest populations or enhance pollination; flowersagricultural production at a larger scale, allowing for and perennial plants may provide habitat and fooduse of machinery. Interactions between plants can sources to predatory beetles and attract bees andtake several forms; they may be either beneficial or butterflies.detrimental. Growing basil and tomatoes togethermay improve the health, flavor or yield of tomatoes. For more resources on trap crops, intercropping andPlants that exhibit allelopathy interfere with companion planting, visit http://organics.utk.edu/neighboring plants (allelopathy refers to release of growers.htm#Companion.chemicals by one plant that inhibit the growth ofanother plant). For example, using ryegrasses as amulch can suppress weeds, but may also suppressthe growth of neighboring plants. Plants may also
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