Common Arugula Pests and Diseases and Their Natural Controls

Arugula is a fast-growing leafy green with a peppery flavor, but like many leafy crops, it can attract pests and diseases. Over decades of growing arugula in both raised beds and containers, I’ve found that early prevention and natural control methods are key to keeping plants vigorous and harvest-ready. Here’s a detailed guide to the most common problems you may encounter and how to handle them without synthetic chemicals.

Table of Contents

Common Arugula Pests

Flea Beetles

Symptoms: Tiny round holes scattered across leaves. Damage is most severe on young seedlings.
Natural Control: Cover seedlings with floating row covers, interplant with strong-scented herbs (like basil or dill), and apply neem oil or insecticidal soap if infestations are heavy.

Aphids

Symptoms: Clusters of tiny green, black, or gray insects on stems and leaf undersides; leaves curl or become sticky.
Natural Control: Rinse plants with a strong jet of water, introduce ladybugs, or spray with a mild solution of neem or insecticidal soap.

Cabbage Loopers and Caterpillars

Symptoms: Ragged leaf edges and frass (caterpillar droppings) on leaves.
Natural Control: Handpick caterpillars early in the morning, encourage predatory wasps, and use Bacillus thuringiensis (Bt) as an organic spray.

Slugs and Snails

Symptoms: Irregular holes in leaves, often with slimy trails on soil and plants.
Natural Control: Set beer traps, use copper tape around beds, and mulch with sharp sand or diatomaceous earth to deter movement.

Common Arugula Diseases

Downy Mildew

Symptoms: Yellow patches on upper leaf surfaces and gray, fuzzy growth on undersides.
Natural Control: Improve air circulation, avoid overhead watering, and plant disease-resistant arugula varieties. Remove infected leaves promptly.

Powdery Mildew

Symptoms: White, powdery coating on leaves that can stunt growth.
Natural Control: Water early in the day to reduce humidity, thin crowded plants, and spray with a homemade milk solution (1 part milk to 9 parts water).

Leaf Spot (Alternaria or Cercospora)

Symptoms: Dark, round spots with yellow halos that can lead to leaf drop.
Natural Control: Rotate crops yearly, keep leaves dry, and remove affected plant material immediately.

General Prevention Tips

Crop Rotation: Avoid planting arugula or other brassicas in the same spot for at least 2–3 years.
Healthy Soil: Add compost to promote strong, pest-resistant growth.
Watering Practices: Water at the base of plants to keep foliage dry and reduce fungal risk.
Companion Planting: Grow arugula near onions, garlic, or nasturtiums to repel pests naturally.

Gardener’s Insight

By combining these organic pest and disease controls with careful crop rotation and healthy soil practices, you can enjoy a long season of clean, peppery arugula without relying on chemical sprays.