The following are highlights and updates about digital and sample submissions for our different services (identification or Plant problem diagnosis from fruit, vegetables, and ornamentals), and questions recently received in the Plant and Insect Diagnostic Clinic.
We are providing digital diagnostics mainly and requesting samples for testing when we deem it critical. We are operating at reduced capacity. Our building is locked to the public. see our guidelines at https://hortnews.extension.iastate.edu/2020/06/guidelines-submitting-isu-plant-and-insect-diagnostic-clinic
Visit the PIDC's Facebook page for updates and more pictures. For more information on a particular disease or insect problem listed, follow the article cited.
Plant Problem diagnosis (with links to articles)
Broadleaf Trees
Anything you can do to promote vigor can help trees to thrive. Consider removing the turf from below the trees and install arborist chip mulch to improve overall health. Otherwise, the tree has to compete with your turf for water. See more information at the Tree and Shrub page.
| Plant | Diagnosis |
|---|---|
| Oak, Maple | Decline, Nutrient deficiency |
| Oak, hackberry | Tatters |
| Oaks | Tubakia leaf spot, Anthracnose, Bot twig canker and dieback |
| Oak, Catalpa, Maple | Transplant shock/stress, plated too deep, Poor Planting Practices and Post-planting Care Drought stress, sunscald/leaf scorch |
| Elm | Dutch elm disease suspected |
| Maple | Verticillium wilt suspected |
Coniferous Trees
| Plant | Diagnosis |
|---|---|
| Arborvitae | Fletcher scale, Spider mite damage |
| Spruce | Stigmina needle cast, Diplodia Tip Blight and Canker, Rhizosphaera needlecast |
| Juniper, Spruce | Spider mite damage |
| Austrian pine, Scots Pine | Dothistroma needle blight |
| Scots Pine | Lophodermium needle blight suspected |
Vegetables
Drip irrigation (using a soaker hose) or directing the hose nozzle as close to the crown of the plant (soil level) can help minimize unnecessary moisture in the leaves and stems. Remember plant pathogens take advantage of excess moisture to reproduce, and water splash to spread.
| Plant | Diagnosis |
|---|---|
| Cucurbits (squash and pumpkin) | Angular Leaf Spot, anthracnose, powdery mildew |
| Tomato | Early blight, various virus, Physiological leaf curl, |
Various vegetables, especially Tomatoes | Suspected herbicide injury, see article: |
| Onion | Purple blotch |
| Garlic | Fusarium Basal rot, virus. |
Fruit
Managing disease in the home orchard takes an integrated approach. From proper pruning and care, to considering fungicide sprays to prevent fruit diseases. Good pruning practices can help reduce the places where pathogen hides (cankers in wood/limbs), while also increasing airflow and minimize moisture that is necessary for plant pathogens to thrive. See the free to download publication Pruning and Training Fruit Trees on https://store.extension.iastate.edu/Product/4094
| Plant | Diagnosis |
|---|---|
| Apple | Frog eye leaf spot/ black rot, Cedar-Apple Rust, aphid, decline, spray phytotoxicity, |
| Pear, Apple | Fire Blight, fungal cankers |
| Peach | Peach leaf curl, wood decay fungi, decline |
| Peach, cherry | Gummosis |
| Raspberry | cane/spur blight |
| Strawberry | Black Root Rot |
Perennials and Annuals
| Plant | Diagnosis |
|---|---|
| Hollyhock | Hollyhock rust |
| Peony | Peony leaf blotch |
| Hosta | Sunscald, Anthracnose, leaf spot, virus |
| Various host | Chemical injury suspected, see article preventing herbicide injury in the landscape |
Preventative application of fungicides can help minimize damage to fruit these two publications have very good information including sprays: Managing Pests in Home Fruit Plantings (Purdue University) and Fruit Spray Schedules for the Homeowner (University of Missouri).
Turf/lawn
Smut, Slime mold, brown patch, leaf spot melting out
Best practices for irrigating your lawn to minimize disease problems:
- Most lawns may only need to be watered under heat and drought conditions (4-6 wks of dry conditions)
- Water early in the morning (4am- 8am), this will mean less water will evaporate, more water to the root system!
- Water infrequently but deeply! meaning turf should be irrigated with 1 to 1-1/2 inches of water in one thorough irrigation. More on lawn irrigation in the publication Irrigation practices for Homeowners
Links to this article are strongly encouraged, and this article may be republished without further permission if published as written and if credit is given to the author, Yard and Garden, and Iowa State University Extension and Outreach. If this article is to be used in any other manner, permission from the author is required. This article was originally published on July 10, 2020. The information contained within may not be the most current and accurate depending on when it is accessed.