The sycamore tree, belonging to the Platanus species, is known for its striking, exfoliating bark that reveals white, tan, and green inner layers. While generally robust, these large, fast-growing trees are susceptible to several common insect pests that can compromise their aesthetic appeal and health. This article provides a focused look at recognizing the signs of infestation and outlines effective management strategies specific to the sycamore.
Common Signs of Pest Infestation
A tree under insect attack often displays visible symptoms that serve as early warning signs of stress. One common indicator is the premature yellowing or stippling of the leaves, appearing as tiny, bleached-out dots on the upper surface. This discoloration results from sap-feeding insects removing chlorophyll-rich material from the foliage. Another clear sign is honeydew, a sticky, sugary liquid excreted by sap-sucking pests. This residue often coats the leaves or the pavement beneath the canopy, frequently leading to the development of sooty mold, a black fungus that feeds on the sugar. On the bark, look for small, sawdust-like piles known as frass, which are the excrement and wood shavings left by wood-boring larvae tunneling beneath the surface.
Identifying the Most Frequent Sycamore Pests
The Sycamore Lace Bug (Corythucha ciliata) is a frequently encountered pest named for the intricate, lacy pattern on its wings. Adults and their spiny nymphs feed exclusively on the underside of sycamore leaves using piercing-sucking mouthparts. This feeding causes the characteristic white or yellow stippling visible on the upper leaf surface, which can progress to a grayish or bronzed appearance with heavy populations. The presence of black, varnish-like specks of excrement, or “tar spots,” clustered on the leaf underside confirms a lace bug infestation.
Sycamore Scale are small, sedentary pests that resemble tiny bumps on the bark or leaves. The Sycamore Scale (Stomacoccus platani) is particularly damaging, causing pock-marked, necrotic spots on the leaves and sometimes abnormal flaking of the smooth bark. Scale insects are often difficult to spot because they are concealed by a white, cottony or waxy material they secrete. This material is most visible in bark crevices and on tender bark.
Wood-boring pests, such as the Sycamore Borer (Synanthedon resplendens), pose a threat by tunneling into the inner bark of the tree. The adult is a clearwing moth that mimics a yellow jacket wasp, and its larvae are responsible for the damage. Infestation is primarily identified by the accumulation of reddish-brown, granular frass, which resembles coffee grounds, found around the base of the tree or protruding from small holes in the bark. While borer activity often remains limited to the bark tissue, repeated tunneling can cause the bark to thicken, crack, or slough off the trunk and large branches.
Non-Chemical Management Techniques
The first defense against insect damage involves improving the tree’s overall health and reducing environmental stress. Providing deep, infrequent watering is foundational, especially during dry periods, as healthy trees are better equipped to naturally resist pest colonization. Drought-stressed sycamores are more attractive to borers and other opportunistic insects.
Sanitation is a practical non-chemical approach, especially for pests that overwinter in fallen debris. Raking and disposing of fallen leaves in autumn removes overwintering eggs and adults of pests like the sycamore lace bug, disrupting their life cycle. Strategic pruning also helps by removing heavily infested small branches, immediately reducing the pest population. Thinning the canopy improves air circulation, which creates a less favorable environment for fungal issues and sap-feeding insects.
For small, localized infestations, a strong jet of water from a garden hose can physically dislodge soft-bodied insects from the foliage. Directing the spray toward the undersides of the leaves is most effective for removing nymphs and adults of pests like lace bugs and aphids. This technique provides immediate relief and reduces the need for chemical applications.
Targeted Treatment Options
When non-chemical methods are insufficient to manage a severe infestation, targeted treatments can be introduced. Horticultural oils, including dormant and summer oils, are options for suffocating soft-bodied pests and the overwintering stages of scale insects and lace bugs. Dormant applications are typically applied in late winter or early spring before bud break, targeting pests hidden in bark crevices.
Insecticidal soaps are a low-impact chemical choice that works well on contact against lace bug nymphs and aphids. These soaps break down the insect’s outer layer, leading to dehydration, and require thorough coverage, particularly on the leaf undersides where pests feed. Since they have no residual effect, they are less harmful to beneficial insects that prey on the pests.
For difficult-to-control pests, such as borers or scale insects on large trees, systemic insecticides are often necessary. These products, such as those containing imidacloprid, are applied to the soil where the tree absorbs them into its vascular system. The chemical then makes the foliage and inner bark toxic to feeding insects, providing protection for an entire growing season.