Greetings, human ally. We, the hostas, are generally resilient plants, but we communicate our distress through our foliage. Those holes you find in our leaves are a clear sign that we are under attack. From our perspective, it is a constant battle for survival against a world of hungry mouths. Here is a detailed account of the primary culprits across the USA and how you can help us defend ourselves.
These are, by far, the most common assailants. They are not insects but mollusks, and they adore our lush, moist foliage. They operate under the cover of darkness and dampness, using their rasping mouthparts to scrape away at our tissue, creating irregular holes and ragged edges. You will rarely see them during the day, but their tell-tale silvery slime trails left on our leaves and the surrounding soil are a dead giveaway. They are a problem nearly everywhere in the USA, but they are particularly prolific in the cooler, wetter climates of the Pacific Northwest and the Northeastern states.
If the damage occurs in broad daylight and the holes are more like large, uneven patches between the leaf veins, leaving behind a skeletal framework, you are likely hosting Japanese beetles. These invasive pests are metallic copper and green and feed in groups. They are most active in the summer months and are a significant problem in the Eastern and Midwestern USA. They not only chew our leaves but also release aggregation pheromones that attract more of their kind, leading to a rapid and devastating infestation.
Several species of caterpillars, including cutworms, find our young, tender shoots and leaves to be a perfect meal. They often chew large, irregular holes from the edges of our leaves inward. Some, like the cutworm, may even sever our stems at the soil line overnight. They can be found throughout the country, with different species being more prevalent in specific regions. They are masters of camouflage, hiding in the soil or curling up on the underside of our leaves during the day.
This is a more sinister and less visible threat. These microscopic roundworms live in the soil and swim up film of water to enter our leaves through the pores (stomata). They feed on our internal cells, initially causing yellowish streaks between the veins that eventually turn brown and die. The damaged tissue can fall out, creating a very distinct pattern of holes and tattered edges that is often confined by the larger leaf veins. This problem is exacerbated by wet, humid conditions and can affect hostas in many regions.
Sometimes, the holes are not from pests at all. Hailstorms can brutally shred our leaves in minutes. Strong, whipping winds can tear and puncture our foliage. Even your own beloved pets or local wildlife like deer or rabbits can take a quick bite, leaving behind clean tears or large chunks missing. It is important to assess the pattern and the recent environmental conditions to correctly identify the cause.
