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Marin IJ Articles

What’s nibbling my vegetables at night?

  • Karen Gideon
  • After spending hours raising seedlings, preparing soil, and planting your vegetable garden it’s disheartening to discover that your plants have been chewed up or removed at night. You can inspect your young plants in the daylight, but by then the pest is long gone. If you know what to look for, you can find some remnant of the night visitors and put together a plan for pest deterrence and elimination.

    Arm yourself with a magnifying glass or loupe and bring your camera to record evidence. Upon inspection of young plant leaves, the most common find is holes or missing leaves. Note the size of holes and look for black crumb-like material on the leaves.  The edges of the leaves might have ragged chunks missing. The night raiders that leave this type of damage are slugs, earwigs, caterpillars and beetles.

    Daytime investigations might reveal a silvery slime trail left behind by a slug or snail. Ragged leaf edges are a common trait of earwigs.  Beetles may leave behind a cluster of eggs, or tiny larvae as they drop off the leaf and scurry out of sight. Round holes and black crumbs on the leaves may indicate that caterpillars are present.  Look for black fecal material and run your fingers through the soil – you may find a caterpillar curled up in the soil.

    To identify your pest directly, inspect your plants after dark and bring your headlamp and camera with you. This is when most of the invertebrates munch your plants and lay their eggs. Flip the leaves over to reveal the slugs and insects. Recording their presence with your camera will give you the most accurate record for your research.

    One of the most destructive caterpillars is the hornworm.  The eggs are laid on the leaves of the tomato plant and grow into caterpillars that can be four inches long. In the caterpillar stage they consume leaves, branches and fruit.  After feasting on your plants, they fall to the ground and dig into the soil to begin pupating.

    If the damage on your plants is round holes and yellow spots, more than likely the culprit has sucking mouthparts.  Common aphids and whiteflies leave this type of damage and may be seen during the day.  Look for the tiny insects and the sweet honeydew they leave behind.

    As we move up the pest food chain the damage gets more pronounced.  Stems may be severed, whole leaves missing or your plants may disappear altogether. If the plants were bearing fruit, it might have big bites or be missing completely. Common garden pests that leave this type of damage include rabbits, voles, rats, squirrels, chipmunks or deer. 

    Look for evidence.  In the case of rabbits, they leave pea-sized poop on the surface. Rabbits’ large front teeth make straight, clean cuts. Voles are voracious eaters of leaves and stems. Their tunnels and trails can be seen leading to the damage. Deer leave hoof prints in the soil and may rip the plants completely out of the ground.  They leave larger poop balls behind.  Rats, squirrels and chipmunks like to eat the fruits like tomatoes and strawberries – nibbling on each piece of fruit so you can’t.

    After you’ve identified some suspects, head to the Integrated Pest Management website http://ipm.ucanr.edu/index.html for help. You can search for your pest by vegetable or the pest’s name. There you will find ways to manage your problem.  Some safe options might include hand removal of pests, washing off predators with soapy water, trapping or allowing natural enemies to control the pest. Some invertebrates enjoy the plants when they are young and tender and eschew them as the plants grow older. 

    For vertebrates, building a fence into the design your garden is a good first step. Fencing needs to be structured with the height of the prowler in mind. Some gardeners use repellents that might include animal urine, cayenne, garlic or hot pepper.  Read labels carefully and follow directions to keep your vegetables safe and edible.