Got Holes in Your Rhubarb Leaves? How to Identify the Culprit

Rhubarb is a hardy perennial vegetable that produces tasty tart stalks ideal for pies, jams, and more. The large rhubarb leaves provide an energy boost for the plant through photosynthesis. But sometimes, gardeners notice damage to the leaves – holes chewed right through them! If you’ve got a rhubarb leaf nibbler in your garden, read on to learn how to identify the pest and protect your rhubarb crop.

Common Rhubarb Leaf Eaters

A wide range of bugs, critters, and diseases can take bites out of rhubarb leaves. Here are some of the most likely suspects to check for:

Slugs and Snails

The ragged holes chewed in rhubarb leaves are a telltale sign of slug and snail damage. These slimy pests feed at night and hide in moist, shady spots during the day. Check under boards, rocks, or debris around the rhubarb for these nighttime nibblers.

Insects

Many insect pests are attracted to the succulent foliage of rhubarb plants. Watch for signs of:

• Caterpillars – Look for green worms on the leaves and the presence of black frass (caterpillar poop).

• Earwigs – Inspect leaves closely for small jagged bites along the edges

• Beetles – Scan for adult beetles like flea beetles, as well as leaf mining larvae.

• Leafhoppers – Check the undersides of leaves for small sap-sucking insects

Diseases

Fungal diseases like leaf spot can also cause small holes or spots in rhubarb leaves Inspect the spots closely – are they brown/grey with defined edges? This points to a fungal infection

Environmental Damage

Abiotic factors can sometimes damage rhubarb leaves too. Consider if:

• Hail or heavy rain caused punctures and tears.

• Sunscald created brown lesion-like spots on leaves.

• Wind tattered and shredded the leaf edges.

• Chemical sprays or fertilizer burn made holes.

Inspection Tips: How to Find the Culprit

Finding the exact pest or problem damaging your rhubarb requires some sleuthing. Follow these tips:

• Inspect leaves closely using a magnifying glass to identify clues like insects, eggs, frass, etc.

• Check under leaves for pests like aphids. Shake leaves over paper to dislodge insects.

• Search for slugs and snails on night patrols with a flashlight.

• Monitor for patterns – new hole formations indicate active feeding.

• Consider weather factors like hail or environmental causes.

• Send samples to a lab for diagnosis of diseases.

• Take photos to show garden center staff for identification.

Common Rhubarb Leaf Nibblers and How to Control Them

Once you’ve identified the culprit eating your rhubarb leaves, you can take targeted steps to control the pest or disease. Here are some common rhubarb nibblers and tips to stop them:

Slugs & Snails

• Remove hiding spots like boards and debris around the plants.

• Use diatomaceous earth sprinkled around the rhubarb to deter and dehydrate slugs and snails.

• Set out shallow dishes of beer to attract and trap them.

• Apply slug and snail baits or treat with iron phosphate. Reapply after rain.

Caterpillars

• Manually pick off any caterpillars you see and drop them in soapy water.

• Spray plants with Bacillus thuringiensis (Bt), a natural bacteria that targets caterpillars but is safe for humans.

• Use lightweight row cover over plants to form a barrier.

Earwigs

• Trap earwigs in overturned pots stuffed with damp straw placed near plants.

• Apply insecticidal soap sprays to deter earwigs and other insects.

• Encourage natural predators like birds that eat earwigs.

Beetles

• Cover young plants with floating row cover to exclude beetles.

• Apply neem oil, which repels many beetle species naturally.

• Dust diatomaceous earth on leaves to deter and dehydrate beetles.

Leafhoppers

• Blast plants with water to knock leafhoppers off leaves.

• Apply sticky barriers like Tanglefoot around plant stems to trap them.

• Use aluminum mulch to deter leafhoppers. The reflection confuses them.

Leaf Spot Fungal Disease

• Improve air circulation and avoid wetting foliage when watering.

• Apply fungicidal sprays containing chlorothalonil or copper early in the season.

• Remove and destroy severely infected leaves and plants to prevent spread.

Prevent Rhubarb Leaf Damage in the First Place

A little prevention goes a long way to keeping rhubarb leaves pest and disease-free. Try these proactive tips:

• Cover young plants with row cover to exclude early insect pests.

• Keep the rhubarb patch weed-free to eliminate hiding spots.

• Clean up and destroy rhubarb leaves and stalks after harvest.

• Use drip irrigation instead of sprinklers to keep foliage dry.

• Rotate rhubarb plantings to new beds every 3-5 years to prevent disease buildup.

• Apply a thick mulch layer to discourage slugs and snails.

• Fertilize plants as needed to promote vigorous, healthy growth.

Don’t Worry About a Few Holes

A small amount of rhubarb leaf damage is not cause for alarm. The large leaves can tolerate some nibbling without harming the overall plant or crop. Focus on identifying the pest and taking simple steps to prevent major leaf loss. As long as the rhubarb stalks remain healthy, your crop will still thrive and deliver a delicious harvest!

With their bold size and succulent texture, rhubarb leaves are magnets for pests. But don’t let a few holes spoil your enjoyment of this tasty perennial. Identify which critter is nibbling your rhubarb and take action to protect the leaves. Implementing prevention methods can stop most leaf damage before it starts. Then you can relax and await your first sweet-tart rhubarb harvest of the season!