Noticed these thick, silky spiderweb nests appearing in the forks of my cherry tree branches this morning. They are filled with fuzzy crawling bugs. Should I be worried about my tree? What is this?

This morning, you might have noticed some peculiar formations in the forks of your cherry tree branches—thick, silky web nests filled with fuzzy crawling bugs. These webs can appear almost overnight and might seem alarming at first glance. While they may look like something out of a horror movie, these nests are actually a common sight in many gardens and orchards.

These woven structures are more than just a curiosity; they are the handiwork of certain insects that can have an impact on the health of your trees. If you're wondering whether you should be concerned about your cherry tree and what steps you might need to take, read on to explore the facts behind these mysterious webs.

The thick, silky nests you're seeing are likely the work of Eastern tent caterpillars (Malacosoma americanum). These caterpillars create web-like nests in the forks of tree branches, particularly in cherry and other fruit trees. The nests serve as communal homes for the larvae, providing protection from predators and harsh weather conditions. Each nest can house hundreds of caterpillars, appearing as a dense, silky mass that is easily noticeable against the tree's foliage.

Eastern tent caterpillars can be distinguished from other web-making pests by their distinct blue and white stripes running down their backs, coupled with a row of white spots. In contrast, fall webworms, another common web-making species, create their nests at the ends of branches and their larvae are covered in fine, white hairs. Eastern tent caterpillars typically build their nests in the tree's crotches, making the location of the webs a key identifying factor.

Cherry trees, along with apple and crabapple trees, are favored targets for Eastern tent caterpillars due to their nutritional value and the timing of their budding. These trees often leaf out early in the spring, providing an abundant food source for the young caterpillars that hatch around the same time. The caterpillars feed on the tender new leaves, which can sometimes lead to defoliation if the infestation is severe.

While an Eastern tent caterpillar infestation can be unsightly, these pests rarely cause long-term damage to healthy, mature trees. Most trees can withstand the temporary defoliation, and new leaves often regrow within the same season. However, young or stressed trees might be more vulnerable, and repeated infestations over several years can weaken a tree, making it susceptible to other health issues.

The fuzzy bugs inside the webs are caterpillars that spend their days emerging from the tent to feed on nearby leaves. They return to the safety of the nest during the night or in inclement weather. As they grow, they molt several times, shedding their old skin to emerge larger and hungrier each time. This feeding and resting cycle continues until they are ready to pupate and transform into adult moths.

Eastern tent caterpillar nests typically appear in early spring, coinciding with the budding of their favored host trees. The caterpillars hatch from eggs laid the previous year and build their nests shortly after. The nests persist for several weeks, during which the caterpillars feed and grow. By early summer, they leave the nests to pupate, and the webs gradually disintegrate, often by mid-summer.

Controlling Eastern tent caterpillars can be effectively managed through manual removal of the nests. Early in the morning or late in the evening, when the caterpillars are inside the tent, prune out the infested branches and dispose of them in sealed bags. For larger infestations, spraying the tree with Bacillus thuringiensis (Bt), a natural bacterial insecticide, can target caterpillars without harming beneficial insects. Always follow label instructions to ensure safe application.

If the infestation is large or your tree is particularly valuable, consulting a professional arborist might be a wise decision. Arborists can assess the health of your tree and recommend a treatment plan. They can also safely apply insecticides if necessary and provide advice on preventing future infestations. Persistent problems over multiple seasons are another indicator that professional help may be needed.

Preventing future infestations involves a combination of monitoring and proactive care. In the fall, inspect your trees for egg masses, which appear as shiny, varnished bands around twigs. Scrape these off and dispose of them to reduce the number of caterpillars that will hatch in spring. Maintaining tree health through proper watering, mulching, and fertilization can also make trees less susceptible to pest infestations.

One common myth is that webs indicate a sick or dying tree. While web nests can stress a tree if the infestation is severe, they do not necessarily mean the tree is unhealthy. Another misconception is that all web nests are harmful. In truth, many web-building insects are part of the natural ecosystem and do not cause significant harm to trees. Understanding the specific pest involved is key to responding appropriately.

It's important to assess the extent of the infestation before deciding on a course of action. If the nests are small and few, and your tree is otherwise healthy, you can often let nature take its course. However, if the tree is young, or the infestation is large and causing significant defoliation, intervention may be necessary. Regular monitoring and early intervention can help protect your trees without resorting to drastic measures.