Arborvitae are popular evergreen conifers, valued for their dense foliage and versatility in landscape design. Gardeners often choose them for their aesthetic appeal. However, a common question is their susceptibility to insect activity. This article details common pests and effective management strategies.
Do Arborvitae Attract Bugs?
Arborvitae naturally interact with a variety of insect life. While they can host certain insect species, arborvitae are not inherently more attractive to bugs than many other common landscape plants. The presence of some insects is normal.
Many insects found on plants are benign or beneficial, contributing to pollination or preying on other pests. However, under specific conditions, certain insect populations can increase, leading to noticeable damage. Understanding this interaction helps distinguish between typical insect presence and a developing pest problem.
Common Pests of Arborvitae
Spider Mites
Spider mites are minute arthropods, often less than 0.5 millimeters, making them difficult to see without magnification. They feed on the undersides of arborvitae needles, piercing plant cells and causing tiny yellow or white spots, known as stippling, on the foliage.
As mite populations grow, stippling becomes more widespread, leading to a bronze or faded appearance. In severe infestations, fine webbing may be visible, particularly around branch crotches. Mites thrive in hot, dry conditions, and their damage is most apparent during summer stress.
Arborvitae Leafminers
Arborvitae leafminers are the larvae of small moths that tunnel within the needles. Adult moths lay eggs on foliage, and upon hatching, larvae burrow into the needles to feed, creating hollowed-out sections.
Initial damage appears as discoloration, with affected needle tips turning yellow, then brown, and eventually dying back. Close inspection of these browned tips often reveals characteristic tunnels or mines. Infested areas can become noticeably sparse and discolored.
Bagworms
Bagworms are the larvae of a moth known for constructing distinctive, spindle-shaped bags from silk and plant material. These bags serve as protective coverings for the caterpillars as they feed and grow, increasing in size up to two inches.
These pests consume arborvitae foliage, leading to severe defoliation if infestations are left unchecked. The presence of these camouflaged bags, often mistaken for pine cones, is the primary sign of an infestation. Bagworms typically overwinter as eggs within the female’s bag, hatching in late spring.
Scale Insects
Scale insects are small, immobile pests that appear as raised bumps or waxy coverings on arborvitae stems and foliage. They attach to the plant and feed by sucking sap, which can weaken the plant. Their appearance varies, with some resembling small, oval shells, while others are soft and cottony.
Infested plants may exhibit yellowing needles, stunted growth, and premature needle drop. Some scale species excrete honeydew, leading to black sooty mold on the foliage. This mold impedes photosynthesis, stressing the plant.
Managing Pests on Arborvitae
Effective management of arborvitae pests begins with cultural practices that promote plant vigor. Proper planting in well-drained soil and adequate spacing allows for good air circulation, deterring pests and diseases. Consistent watering, especially during dry periods, helps reduce plant stress, making arborvitae less susceptible to infestations.
Regular inspection of your arborvitae is a powerful preventive measure. Early detection of pests allows for targeted interventions. A thorough visual check of the foliage, including undersides of branches, reveals early signs of insect activity or damage.
For localized or minor infestations, non-chemical methods are effective. Hand-picking bagworms and disposing of them before they mature reduces their population. A strong stream of water can dislodge spider mites and some scale insects from foliage.
In cases of severe infestation, targeted treatments may be necessary. Horticultural oils, which work by suffocating pests, are effective against spider mites and soft-bodied scale insects when applied according to label directions. Insecticidal soaps offer another low-impact option for controlling soft-bodied pests, disrupting their cell membranes.