Study shows that intercropped planting helps control pests

Research compiled results from 44 field studies on six continents

09.04.2023 | 09:57 (UTC -3)

Study reveals that intercropped planting can be an efficient pest control tool around the world, according to research from the University of Florida, published in the Journal of Applied Ecology. The study analyzed 44 field studies carried out on six continents, focusing on four types of crops - cabbage, pumpkin, cotton and onion - planted alone or together with other companion plant species.

Scientists recorded 272 occurrences of 35 different species of plant-eating insects in crops, representing one of the most comprehensive assessments of the effectiveness of intercropping anywhere in the world.

"Overall, intercropping proved to be very effective against pests, but it varied based on the dietary preferences of each pest," said Philip Hahn, assistant professor in the UF/IFAS department of entomology and nematology, who led the study.

Intercropping is the technique of planting crops together so that companion plants can help repel or intercept pests before they damage the main crop. Scientists have observed that streak planting, such as "Three Brothers" (corn, squash and beans), makes it harder for pests to locate their preferred host plant and is more effective than border plantings.

Regarding the type of crop, the researchers noted that cabbage and pumpkin showed greater resistance to pests, while resistance was lower for onions and cotton. The researchers also observed that intercropping was more effective for generalist pests that feed on a variety of crops. Specialized pests, which attack only one type of crop, were less affected.

The research provides recommendations for the most effective companion plant combinations, while highlighting pairs that appear less effective. The results of this study will likely influence future investigations, as selections from neighboring plants may be key to the success of intercropping systems. Overall, for growers interested in organic methods, intercropping appears to be a very effective pest control tool.

At the conclusion of the study, the scientists pointed out that:

"Our meta-analysis reinforces the use of bicultures as a pest management tool, albeit with several contingencies. Most agricultural crops have well-resolved relationships between pest abundance and damage levels that are used as 'economic thresholds' for when to apply management actions. Although our meta-analysis clearly shows strong benefits of neighboring plants in reducing pest abundance, the variability we found suggests that incorporating EA into economic decision-making tools such as economic thresholds will require site- and crop-specific information. For example, only two of our four focal crops benefited strongly from pest reduction in bicultures. Techniques in which the neighboring plant was planted within the plot boundaries were more effective than neighboring plants planted around the perimeter of the focal crop. Plot size did not affect AE strength, suggesting that the benefits of bicultures are scalable, at least given the contingencies described above. Our use of herbivore traits and phylogenetic distance from neighboring plants provides a generalizable framework that can aid in decision-making to assess the potential ecological-economic trade-offs of crop diversification. "

The full article can be read here.

What is allelopathy

When considering the data from the research described above, one should also keep in mind allelopathic effects.

Allelopathy is a biological interaction between plants or other organisms, in which chemical compounds produced by one organism affect the growth, development and reproduction of another organism. These chemical compounds are known as allelochemicals and can be produced by the roots, leaves, flowers, fruits and other organs of plants.

In allelopathy, allelochemicals released by a plant can have positive or negative effects on other plants and organisms, depending on concentrations and environmental conditions. For example, some plants may produce allelochemicals that inhibit the growth of other competing plants, while others may produce allelochemicals that promote the growth of nearby plants.

Allelopathy can have important implications in ecology, agriculture and the natural medicine industry, since many bioactive substances can be found in plants and other organisms.

The noun allelopathy was created by Austrian researcher Hans Molisch. It is the union of the Greek words "allélon" (mutual) and "pathos" (harm). Despite the original meaning of the Greek terms, the term allelopathy is used to refer to both negative and positive effects caused by organisms.

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