Issue 7, July 16, 2021
June 2021 Plant Clinic Sample Summary
Summary of ornamental, fruit, and vegetable samples received June 2021.
The Plant Clinic remains open. We are currently operating with reduced staff and are only in the lab as needed for diagnostics and other lab work. We may not be able to answer or return phone calls in a timely manner; MWF are the best days to contact us due to staffing schedules. You can also email us at plantclinic@illinois.edu.
Samples shipped via USPS, UPS, and FedEx are all arriving in a timely manner. We recommend shipping early in the week (Monday-Wednesday) and keeping the tracking number so we can trace the package if needed.
We are receiving more maple and oak samples, while the number of conifer samples is declining. Anthracnose has been found on a number of samples. There are a wide variety of fungi that cause anthracnose diseases on a number of different hosts, including sycamore, maple, and oak trees, and a wide number of herbaceous ornamental and vegetable and fruit plants. Severity of the disease is dependent on weather; cool, wet weather tends to favor the disease. Anthracnose usually causes large, dark brown lesions on leaf tissue. Heavily infected leaves may drop, and trees will often put out a second flush of leaves if the infection is severe enough.
Anthracnose is largely considered an aesthetic disease, though there are exceptions including oak, dogwood, strawberry, and turf anthracnose if the environment is favorable. While the disease can make plants unslightly, it rarely causes lasting damage to otherwise healthy trees. Because of this, chemical management is not recommended (along with the difficulty in getting good coverage in large tree canopies). Management consists of reducing stress on the trees by lightly mulching the base (ideally to the dripline), watering during periods of dryness during the growing season, fertilizing in late fall or early spring with a balanced fertilizer, and pruning out dead branches in dry weather.
We’re still seeing needle blights and needle casts on fir, spruce, and pine, along with leaf scorch on deciduous trees as we get into the hotter weather. Wooly aphids were found on a number of different hosts, including ash, elm, and maple.
We’ve had a few suspected oak wilt samples and one confirmation in Lake County. For more information about this serious disease, see: http://hyg.ipm.illinois.edu/article.php?id=1163 As a reminder, do not prune oak trees during the growing season!
Host |
Pathogens and/or Pests Confirmed (C) or Suspected (S) |
Arborvitae |
Phyllosticta needle blight (C), spruce spider mite (C) |
Ash |
Wooly aphids (C) |
Boxwood |
Volutella blight (C), Fusarium canker (C), Boxwood leafminer (C), boxwood spidermite (S) |
Cedar |
Tipminer/leafminer (C) |
Cherry |
Gummosis (C) |
Elm |
Elmgrass root aphid (C) |
Fir |
Phyllosticta needle blight (C), environmental stress (S) |
Hosta |
Hosta Virus X (C) |
Hydrangea |
Chemical injury (S) |
Hyssop |
Spidermites (C) |
Juniper |
Pestalotiopsis needle blight (C), Phyllosticta needle blight (C) |
Lavender |
Phyllosticta leaf spot (C) |
Leatherwood |
Rust |
Maple |
Wooly aphids (C), Anthracnose (C), Leafhoppers (C), Lecanium scales (C) |
Oak |
Oak twig canker (C), Anthracnose (C), Jumping oak gall (C), Tatters (C), Oak apple gall (C), Oak wilt (C), Environmental stress (S) |
Pear |
Fire blight (C) |
Pecan |
Chemical injury (S) |
Pine |
White pine decline (S), Environmental stress (S) |
Spruce |
Sudden Needle Drop (SNEED) (C), Rhizosphaera needle cast (C), Sirococcus needle blight (C), Stigmina needle cast (C), Spruce bud scale (C), Spruce spidermite (C), Cytospora canker (S), Environmental stress (S) |
Tomato |
Fusarium wilt (C), Tomato Spotted Wilt Virus (TSWV) (C) |
Turf |
Anthracnose (C) |
Witchhazel |
Fungal canker (S), Environmental Stress (S) |
Author:
Diane Plewa