Garden Pests: Combatting Armyworms and European Hornets

Gardeners are increasingly facing challenges with pests as the growing season progresses. Recent inquiries have highlighted concerns regarding the yellow-striped armyworm and its impact on tomato plants, as well as the predatory behavior of European hornets targeting pollinators.

The yellow-striped armyworm is known for creating holes in unripe tomatoes. This caterpillar typically emerges late in the growing season, particularly in regions like Maryland. The insects are usually absent during winter months, as the adult moths migrate northwards with storm fronts from southern areas. However, rising winter temperatures may allow this species to overwinter in the region, potentially leading to earlier infestations.

Gardeners can mitigate the impact of these caterpillars by manually removing them from plants and relocating them to areas where birds can consume them. To prevent their appearance, the use of insect mesh netting can be effective, although it may also limit access for beneficial pollinators. While some vegetables do not require pollination to produce fruit, tomatoes do, making this solution less than ideal.

For those looking to employ chemical solutions, lower-toxicity pesticides such as Bacillus thuringiensis (Btk) and spinosad can be useful. Btk is particularly effective on young caterpillars, while spinosad works across all life stages. Both products are derived from naturally occurring microbes and target caterpillars as they feed on treated foliage. It is crucial to adhere to product label instructions, especially to avoid harming pollinators by preventing spray residue on open flowers. Furthermore, gardeners should ensure that any pesticide chosen is explicitly labeled for use on edible plants, as not all formulations are safe for vegetables. Repeat applications may be necessary after a waiting period to achieve optimal results.

Fortunately, natural predators such as various wasps and birds often help control armyworm populations without the need for human intervention. Although these predators may not eliminate all caterpillars, they can significantly reduce their numbers. While the damage inflicted by armyworms is typically minor, it can still affect tomato harvests. Any fruits showing signs of chewing damage should be composted to prevent further issues.

In another prevalent concern, European hornets have been observed hunting pollinators, leading to frustration among gardeners. These non-native hornets have been part of the local ecosystem for nearly a century, and controlling their population is generally unnecessary. Attempts to eradicate a hornet nest can also pose risks of defensive stings from the colony.

European hornets are known to prey on bees, butterflies, and other pollinators as they navigate blooming plants. While this predation can be alarming, it is important to remember that a significant number of pollinators remain unaffected.

For further guidance on gardening and pest management, the University of Maryland Extension’s Home and Garden Information Center offers a wealth of resources. Gardeners can access free information and submit questions by visiting extension.umd.edu/hgic and selecting “Ask Extension.”

As challenges in gardening evolve, being informed about pest management strategies can help ensure a successful growing season.