Boxwood, Buxus spp., is a popular shrub in Michigan landscapes that is host to the boxwood leafminer, the boxwood mite and the boxwood psyllid. They are tiny spider-like creatures who cause damage when they suck the sap from the leaves of the plant. Prevention & Control: Use of insecticides against boxwood leafminer is not recommended unless damage is intolerable. Plant root rot-susceptible plants in well-drained areas or in raised beds. The pathogen can survive for at least five years on blighted and fallen foliage, as well as on the stem lesions on the dying or dead plants. Crowded growth and dead leaves in the branch crotches tend to maintain high levels of humidity in the canopy, making conditions conducive to dieback diseases. Infestations of two-spotted spider mites result in the bleaching and stippling of leaves. When temperatures warm up, they hatch. are large shrubs or small trees commonly used in formal gardens and informal landscapes as accent, topiary, edging or … Insecticides are most effective against this pest when adults have emerged and before they can lay eggs. On severely fed foliage, color may be brown but it is usually tan. Snow load injury. Various species of nematodes (microscopic worms that feed on the roots) also appear to be involved (see Nematodes section below). These mites may injure ornamental boxwoods, especially in hot, dry seasons. The adult is green to yellowish brown in color, has eight legs and is tiny, about 1/64-inch long. Prevention & Treatment: A thorough diagnosis of the associated factors is important before corrective action is taken. One of the few insects that can cause issues on this resilient plant are boxwood spider mites. Roots are dark and rotted. English boxwood is somewhat resistant. Boxwood Blight (Calonectria pseudonaviculata) The disease is caused by a fungus called Cylindrocladium pseudonaviculatum (synonym: Cylindrocladium buxicola). The online advice is for spring and summer treatments. Volutella blight is not lethal, but will kill individual branches. As with all pesticides, read and follow all label instructions and precautions. There can be eight or more generations per season, which can add up to a lot of insects and some potentially serious damage to your plant. Both the adult and nymph (the immature insect stage which resembles the adult) feed by piercing leaf surfaces and sucking plant sap. Nymphs feed from buds and young leaves. Stems become infected and form dark brown to black lesions or cankers. If you are planting new boxwoods, Michigan State University Extension recommends considering varieties that are insect and mite resistant. Boxwood spider mites, leafminer, and psyllid are all treatable pests that cause foliar damage. If this document didn’t answer your questions, please contact HGIC at or 1-888-656-9988. Hold a white sheet of paper under a branch and strike the branch. Kelly Ivors, Plant Pathologist, California Polytechnic State University, San Luis Obispo, CA. Boxwood Leafminer (Monarthropalpus flavus): This is the most serious insect pest that attacks boxwood. Stippling on top of leaf, grey and fuzzy beneath. Repeated defoliation can kill young plants. Plants in highly exposed situations may require wind protection. If your boxwood leaves are turning yellow, it’s possible that you could have a mite problem. The mite is a serious problem on most B. sempervirens cultivars, particularly those grown in sunny locations. Root Rot: Root rot is caused by the fungi Phytophthora nicotianae and P. cinnamomi. Boxwood psyllid feeding causes cupped, stunted leaves. Join our mailing list to receive the latest updates from HGIC. of Entomology, Soil & Plant Science, Clemson UniversityJoey Williamson, PhD, HGIC Horticulture Extension Agent, Clemson University. Boxwood Spider Mite - Discolored leaves top and bottom. Marjan Kluepfel, Former HGIC Horticulture Information Specialist, Clemson UniversityJanet McLeod Scott, Former Horticulture Information Specialist, Clemson UniversityJames H. Blake, EdD, Extension Associate/Adjunct Professor, Dept. This is due to the toxins in the mites’ saliva. Decline: Boxwood decline is a poorly understood complex involving the fungi Paecilomyces, Volutella, Macrophoma and Phytophthora, as well as cold injury, drought stress, and nematodes (microscopic round worms). Abiotic Disorders & Cultural Problems Adults typically emerge over a three-week period but live only a few days. When the larvae hatch, they feed inside the leaf, creating a mine. For information on species, varieties and culture, see HGIC 1061 Boxwood. By the onset of hot weather (70°F and up), the mites have caused their maximum damage. From a short distance, the infested boxwood appears unhealthy with a dingy silvery color. Circular bumps can be caused by boxwood leafminers (Figure 1) and fine scrapes by boxwood spider mites (Figure 2). Prevention & Control: Naturally occurring enemies of mites include various predator mites, ladybird beetles (ladybugs) and other insects. Around the waist 4. As boxwood blight advances, leaves and stems become more diseased and then defoliation occurs. Boxwood Psyllids. Once you have identified the problem, it’s time to ask yourself how to get rid of spider mites on boxwood. These pests can weaken and disfigure plants. Dead or dying branches occur randomly in the bush. Clemson University Cooperative Extension Service offers its programs to people of all ages, regardless of race, color, gender, religion, national origin, disability, political beliefs, sexual orientation, gender identity, marital or family status and is an equal opportunity employer. Symptoms consist of weak and spindly plants. Adults emerge from the leaves the following spring, just after new growth occurs on boxwoods. By: Bonnie L. Grant, Certified Urban Agriculturist. Spider mites will show up on the white paper and can be counted. If you notice leaves with lots of tiny yellowish or bleached spots, leaves turning pale bronze, scorching around leaf edges, or leaves falling off prematurely, your plant is probably infested with spider mites. Spider Mite Damage on Boxwoods The first sign you have spider mites might be leaf stipling. With these insecticides, begin treatment in mid-April to early May when the adult flies are seen hovering around the boxwood plants. This information is supplied with the understanding that no discrimination is intended and no endorsement of brand names or registered trademarks by the Clemson University Cooperative Extension Service is implied, nor is any discrimination intended by the exclusion of products or manufacturers not named. symptom . This should include a nematode analysis, soil analysis, and evaluations of drainage in the area and the degree of rooting in surface duff (litter). Blistering may not be obvious until late summer. The leaves have lots of tiny yellow spots as well as larger yellow spots 2-3 mm across, and tiny black spots on the underside. Nematodes: Boxwoods are susceptible to several parasitic nematodes (microscopic round worms), including the Southern root-knot nematode (Meloidogyne incognita), the ring nematode (Mesocriconema), the lesion nematode (Pratylenchus), and the stunt nematode (Tylenchorhynchus).