Evaluating the Impact of Intercropping Vegetables and Cut Flowers on Yield and Conservation Biological Control

Authors

• Alliance Igiraneza, University of Nebraska-LincolnFollow

First Advisor

Ronald Christian Stephenson

Date of this Version

5-2026

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Horticulture

Under the supervision of Professor Ronald Christian Stephenson

Lincoln, Nebraska, May 2026

Comments

Copyright 2026, Alliance Igiraneza. Used by permission

Abstract

Specialty crops such as vegetables are some of the most susceptible to yield losses and increased management difficulty over time due to pests. One of the potential solutions to this problem, which aims at ensuring the sustainability of the sector, is using conservation biological control practices such as intercropping to increase diversity, while maintaining the economic feasibility and profitability of the system. This study was conducted to evaluate the impact of this management practice using Bell pepper (Capsicum annuum var. King Arthur) as the main crop, intercropped with flowers including zinnia (Zinnia elegans var. Benary’s Giant), sunflower (Helianthus annuus var. Soraya) and dianthus (D. caryophyllus var. Chabaud Benigna). Multiple variables were measured including yield and marketability, economic return from both intercrops, insect and disease damage, and diversity of arthropod populations; to assess the effect of different treatments. The distance of bell pepper planting from treatment row – whether planted in inner or outer row – did not influence their yield and pest damage in all treatments. Dianthus (and sunflower in the second year) treatment produced significantly greater bell pepper yield than zinnia treatment, but it was not significantly different from the pepper monocrop control. Although bell pepper yield was slightly reduced in zinnia intercrop compared to control treatment, the economic return from zinnia flowers was estimated to be much higher, potentially offsetting any loss. Sunflowers, despite the presence of beneficial insects, were found to have most insect and disease damage. Dianthus treatment had the least arthropod activity – in both beneficial insect population and pest damage. Zinnia treatment was found to have the most diverse and beneficial insect proportion with lesser pest and disease damage pressure. Based on these results, it was concluded that cut flower intercropping with vegetable crops such as bell peppers could potentially lead to benefits by boosting economic returns and enhancing conservation biological control. Further research would be useful in assessing the full economic and biological impact in different commercial field settings, while considering real market situation for economic return estimation.

Advisor: Ronald Christian Stephenson