Before beautiful butterflies or delicate moths flutter in a summer breeze, they must live part of their lives as caterpillars. Unfortunately, caterpillars can do a lot of damage to plants, devouring roots to fruit, bark to leaves. The deeper a caterpillar can bore, like into wood or inside fruit, the harder it is to control. Leaf-eating caterpillars are easier to manage with hand-picking, topical treatments and natural predators. Many plants can handle a few caterpillars.
Leaf-eating caterpillars are obviously drawn to leafy vegetables like lettuce, cabbage, spinach and chard, but they aren’t picky. Leaf-eating caterpillars have big appetites and feast on many vegetable plants. Cole crops, which include broccoli, radish, turnips, cabbage and collards, are attractive to cabbageworm and cabbage looper caterpillars. Beets, peas, potatoes, peppers, onions, asparagus and tomatoes feed and shelter several varieties of leaf-eating caterpillars like tobacco hookworms and beet armyworms.
Caterpillars are common in flower gardens because butterflies are common in flower gardens. Although butterflies don’t hurt plants by collecting nectar, their caterpillar larvae can damage almost every type of flower. Gardeners who want to attract butterflies but avoid damage caused by caterpillars should locate plants that attract butterflies away from those they want to spare from their ravenous larvae. Common host plants for butterflies include bee balm, sunflowers, marigolds, zinnias, asters, cosmos, butterfly bush, sweet peas and verbenas.
Ornamental and fruit trees are often plagued by the larvae of tortricid moths, called leafrollers because they feed and shelter inside rolled-up leaves. Regions with cool, humid summers, such as the San Francisco Bay Area, can attract the light brown apple moth. Ornamental trees targeted by leaf-eating caterpillars include maple, elm, ash, poplar, birch, willow, and live and deciduous oaks, which are particularly vulnerable to damage by leafrollers. Fruit and nut trees can also be infested by caterpillars, with apple, pear, plum, cherry, walnut and almond trees among the most common victims.
Identification and Control
Suspect leaf-eating caterpillars are responsible for the rampant leaf damage in your garden? There are telltale signs. Look for feeding damage ranging from small holes to loss of entire leaves, pellet-like droppings on or under leaves in the damaged areas, rolled leaves and sometimes a thick web. Many caterpillars are night-feeders, hiding below the soil during the day. Control them in an environmentally friendly way by cutting out webs and pruning rolled leaves, and picking caterpillars off plants and dropping them into a bucket of soapy water. Caterpillars also have numerous natural enemies, from birds to wasps to spiders. Attract these beneficial predators to your garden by limiting pesticide use and providing food, water and shelter. For insects, that means planting flowers to provide pollen and nectar. Give spiders mulch to protect them and somewhere to build webs, like between taller plants. Provide birds with birdhouses, a bird bath and, in the winter, seed-filled feeders.
- University of California IPM Online: Pests in Gardens and Landscapes: Leaf-Eating Caterpillars.
- UMass Extension Center for Agriculture: What’s Eating My Vegetables? Page 1
- Washington State University King County Extension: Organic Pest Control in the Vegetable Garden, page 2, Cabbage Worms and Cutworms)
- University of California IPM Online: Leafrollers on Ornamental and Fruit Trees
- University of California IPM Online: Pests in Gardens and Landscapes: Foilage-Feeding Caterpillars.
- Colorado State University Extension: Attracting Butterflies to the Garden
- North Carolina Agricultural Extension Service: Insect Pests of Vegetables: Moths, Butterflies and Their Young (Caterpillars)
- University of Minnesota Extension: Caterpillar Pests of Cole Crops in Home Gardens
- University of Colorado: Pest Control: Growing Plants to Attract Beneficial Insects
- Colorado State University: How to Increase the Number of Spiders in Your Garden
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