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Intercropping for Insect Pest Management

Companion plants can be planted to attract beneficial insects, including pollinators and natural enemies.

Intercropping Method for Conservation Biocontrol of European Corn Borer Ostrinia nubilalis (Lepidoptera: Crambidae) in Bell Peppers.

Matthew W. Bickerton, George C. Hamilton

Demonstration Design: This study was designed with the goal of enhancing biological control by natural enemies of European corn borer (ECB) in bell pepper. Intercropped plants used were selected to attract predators of ECB. The study was conducted at two research farms in New Jersey (Pittstown and North Brunswick) over the course of three growing seasons.

Pest: European corn borer
European corn borer is the primary insect pest of pepper in New Jersey. Oviposition in peppers occurs during second flight (typically late June through August). Peak adult activity occurs in mid-to-late May, mid-July, and late August-early September.

Predators: Three predators: minute pirate bug (Orius insidiosus), pinkspotted lady beetle (Coleomegilla maculata), and green lacewing larvae (Chrysopa, sp.)

Main Crop: Bell pepper

Intercrops: Dill, Coriander, Buckwheat

Set-up: Dill (Anethum graveolens), coriander (Coriandrum sativum), and buckwheat (Fagopyrum escuelentum) were planted in 5 successive rows on the southern edges of bell pepper plots. Two reps received weekly foliar sprays of spinosad and two were unsprayed.

Planting: Coriander and dill were planted together in double rows. Coriander and dill were planted in the greenhouse in April and transplanted in May-early June and in late June. Buckwheat was planted in single rows on bare ground. There were three plantings of buckwheat: once in early June, once in late June-early July and once in July-early August. Peppers were seeded in the greenhouse in April and transplanted in June in single rows on black plastic.

Findings: Overall, the research establishes intercropping as an effective control method for ECB, particularly at high ECB densities. Intercropping enhanced predation of ECB eggs by minute pirate bug (Orius insidiosus) and pink spotted lady beetle (Coleomegilla maculata). Furthermore, in intercropped plots, percentages of damaged fruit were reduced – this was particularly evident in plots with high ECB density. At low ECB densities, biological control by natural enemies was insignificant.

The benefits of intercropping declined with increasing distance from the flowering plants. Predation by the most important predator (pink spotted lady beetle (Coleomegilla maculata)) was higher in intercropped plots than in non-intercropped plots only in pepper rows < 45 ft from the flowers.

This work also found that, at high ECB densities, the use of selective insecticides (e.g. Spinosad) may disrupt natural enemy activity and thereby decrease the beneficial effects of intercropping.

How does this study apply to my farm?
Variations in insecticide use, alternative prey sources, and natural enemy and ECB populations will impact conservation biocontrol efforts on larger farms.  
Furthermore, weather conditions affect insect behavior. When weather conditions are unfavorable for predators, i.e. cool temperatures and high precipitation, predation may be inhibited and the beneficial effects of intercropping may therefore be insignificant.

What if there are alternative prey species?
Availability of alternative prey can interfere with predation of European corn borer. In this study, when green peach aphids were available, predation of ECB was reduced.

What else can I do to control European corn borer on pepper?
Locate pepper plots as far away as possible from corn.
Incorporate plant residues after harvest.
You can follow the spread of European corn borer throughout New Jersey. Rutgers Cooperative Extension Vegetable IPM Program produces and disseminates European corn borer maps weekly from May through October using data from blacklight traps distributed throughout the state. Maps and accompanying text are published in the Plant and Pest Advisory