Arugula, a peppery and fast-growing leafy green, is a popular choice for home gardeners, but its quick growth cycle and bright foliage make it a prime target for a variety of garden pests. As a member of the Brassicaceae family, arugula shares characteristics with cabbage, broccoli, and mustard greens, which are highly attractive to specific insect species. This genetic relationship means the plant is susceptible to a predictable cast of characters. Understanding these common invaders and employing a layered defense strategy is the most effective approach to ensuring a healthy harvest.
Identifying Common Arugula Invaders
The first step in pest management involves accurately identifying the culprit by the specific damage it leaves behind.
Flea Beetles
One of the most common issues is caused by flea beetles, small, dark-colored beetles named for their habit of jumping away quickly when disturbed. Their feeding activity leaves behind a distinctive pattern of tiny, round holes scattered across the leaf surface, often described as a “shotgun” effect.
Aphids
Aphids present a different, yet equally damaging, problem by congregating in dense colonies on stems and the undersides of leaves. These minute, pear-shaped insects are sap-suckers, which results in stunted growth, yellowing, and leaf curling. As they feed, they excrete a sticky, sugary substance known as “honeydew,” which can then lead to the growth of black sooty mold on the leaves.
Cabbage Worms and Loopers
The larger, more visible damage is often the work of cabbage worms and loopers, which are the larval stages of various moths and butterflies. These caterpillars consume entire portions of the leaf, leaving behind large, irregular holes and ragged edges. This damage is often accompanied by visible dark green or brown fecal pellets, called frass.
Non-Chemical Prevention Strategies
Proactively protecting the crop is the most effective way to avoid the need for reactive treatments.
Physical Barriers
One of the best physical barriers is the use of floating row covers, which are lightweight fabrics draped over the plants and secured at the edges. This netting allows light and water to pass through but physically prevents adult insects, like the Cabbage White butterfly and flea beetles, from landing to feed or lay eggs.
Cultural Practices
A long-term strategy is practicing crop rotation, which involves avoiding planting arugula or other Brassica family members in the same spot for two to three years. This disruption helps break the life cycle of soil-borne pests and those that overwinter in the garden bed. Additionally, ensuring proper plant spacing and consistent watering reduces plant stress, making the plants less susceptible to colonization.
Companion Planting
Companion planting works as a deterrent, using strong-smelling aromatic plants to confuse or repel pests. Planting herbs like dill, basil, or thyme near arugula can help mask the scent of the susceptible crop. Similarly, planting trap crops, such as radishes or certain mustard varieties, can attract pests away from the arugula, concentrating the infestation on a plant intended for sacrifice.
Organic Pest Management and Treatment
When a pest infestation is discovered, reactive organic treatments can be employed to manage the population and salvage the harvest.
Manual Removal
For larger pests, like cabbage worms and loopers, the most direct method is hand-picking them off the leaves and stems. This manual removal should be done regularly, especially in the morning, and can be paired with removing any visible egg clusters found on the undersides of leaves.
Organic Sprays
For smaller, soft-bodied insects like aphids, treatment often involves the application of organic sprays. Insecticidal soap works by breaking down the insect’s protective outer layer, leading to dehydration and death, but it only kills the pests it directly contacts.
Neem oil, derived from the seeds of the neem tree, is another widely used organic insecticide that acts as a repellent and disrupts the hormonal systems of insects. It must be applied in the evening or early morning to avoid leaf burn.
Diatomaceous Earth (DE)
Diatomaceous earth (DE), specifically the food-grade variety, is a powdery substance made from the fossilized remains of diatoms. When dusted around the base of plants or lightly over the foliage, its microscopic sharp edges cut the exoskeletons of crawling insects, causing them to dehydrate. For this method to remain effective, it must be reapplied after any rain or overhead watering.