Ferns are a diverse group of plants found in various climates. They play a significant role in ecosystems, helping to stabilize soil and prevent erosion with their root-like structures called rhizomes. Ferns also contribute to nutrient cycles and provide habitat for different species, including serving as a food source for some animals and insects.
Common Invertebrate Pests of Ferns
Small invertebrate pests often target ferns, particularly those in gardens or as houseplants. Slugs and snails are common culprits that chew irregular holes in fronds, leaving behind characteristic slimy trails. These mollusks are most active in wet, humid conditions, and their feeding can lead to weakened growth.
Sap-sucking insects also pose a threat to ferns. Aphids, tiny soft-bodied insects, feed on plant sap, causing fronds to curl, yellow, or become distorted. They excrete a sticky substance called honeydew, which can attract sooty mold.
Mealybugs appear as small, white, cottony masses, clustering in leaf axils and on stems, and their sap-sucking activity can lead to stunted growth and leaf drop. Spider mites are minuscule pests that cause speckling or yellowing of leaves and leave fine webbing on the plant, thriving in hot and dry conditions. Fern scale, another sap-sucking insect, has a protective armor and causes slow dieback.
Larger Vertebrate Herbivores of Ferns
Larger vertebrate animals also consume ferns. Deer browse on fern fronds, especially when other food sources are scarce. They may be drawn to certain varieties like royal and autumn ferns, particularly when sprouting. Rabbits are another common vertebrate that will eat ferns, including young bracken ferns.
Livestock, such as cattle and sheep, can also consume ferns. However, consuming certain fern species can lead to adverse health effects, which is important for land managers and livestock owners to consider.
Protecting Your Ferns
Protecting ferns from pests and herbivores involves a combination of strategies. Physical barriers can deter larger animals like deer and rabbits from accessing fern beds. For slugs and snails, copper tape or sharp-edged barriers placed around plants can be effective deterrents, as copper reacts with their slime, creating an unpleasant sensation. Manual removal of slugs and snails during their active periods, such as early morning or after rain, can also significantly reduce their populations.
Cultural practices also help prevent infestations. Ensuring adequate air circulation around ferns can deter pests, and maintaining high humidity levels can help prevent spider mite infestations, which prefer dry conditions. For indoor ferns, regularly wiping leaves with a damp cloth can remove eggs or larvae of pests. Companion planting with certain species that slugs and snails dislike, due to thick leaves or bitter sap, may also offer some protection.
Are Ferns Toxic to Some Animals?
While some animals consume ferns, certain species are toxic and can cause harm. Bracken fern is particularly notable for its toxicity to livestock and horses. It contains thiaminase, an enzyme that inactivates thiamine (vitamin B1), leading to thiamine deficiency in horses. Symptoms in horses can include weight loss, incoordination, muscle tremors, and a crouching stance.
In cattle, bracken fern toxicity often manifests as a hemorrhagic disease due to a compound called ptaquiloside, which affects bone marrow and can lead to bleeding and even cancer of the bladder. Symptoms in cattle include high fever, loss of appetite, difficulty breathing, and nasal or rectal bleeding.
The toxic effects are cumulative, appearing after significant consumption over weeks or months. While sheep are more resistant, they can also be affected. Cats and dogs can also be susceptible to bracken fern poisoning.