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Tag: plant disease

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It's that time of year when landscapers and homeowners bring in oak leaves and leaves from other hardwoods such as maple and elm with scorched edges, to be tested for bacterial leaf scorch. Currently, there is a $20 charge per sample for bacterial leaf scorch (BLS) testing. For BLS testing, at least 20 leaves are required and the test may take up to two weeks to run. Check payable to University of Delaware.
Due to similarity of symptoms to other environmental and cultural disorders, a confirmation diagnosis is based on detection of bacteria in plant tissue. A laboratory test necessary to detect presence of causal bacteria relies on sampling approximately 15-20 petioles of leaves. Attached leaves provide the best specimens, for leaves collected in September. A positive detection of bacteria along with dieback indicates the tree in question will survive only a few years. Severely affected trees should be removed to reduce spread to nearby trees. The bacteria that cause BLS are not harmful to humans or animals.
Checks payable to University of Delaware, $20 per sample. Please indicate on the form that BLS testing is requested. http://extension.udel.edu/ag/plant-diseases/ud-plant-diagnostic-clinic/how-to-submit-a-sample/  Delaware Cooperative Extension office staff may receive plant samples in the County Offices.
NFG August 2019

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PanAmerican Seed announced a series of I. walleriana with resistance to Impatiens downy mildew. Beacon Impatiens, according to a press release, offer season-long performance and color to the shade without the disease risk.  "... we are confident that our greenhouse customers, retailers and gardeners alike will have the confidence to grow garden Impatiens once more.”  “With a plant structure, flowering time and flower size that is similar to existing Impatiens, ... There’s no special plant culture required for Beacon to be successful. Beacon Impatiens will have its debut at shows in 2019, with six core colors and two mixes in the series. A limited supply is available, with greater availability in 2020.


Syngenta Seed also has a release of resistant impatiens, the Imara TM series: https://www.syngentaflowers-us.com/campaign/imara-XDR-impatiens .  Impatiens walleriana with a high degree of resistance to downy mildew.*  Proven landscape performance  with reliable flowering all season long. Easy and economical, ideal for growing in packs and pots.  ‘Welcome Back!’ to a favorite shade bedding plant.

*Confirmed in independent trials in North America and Europe, in 2017-18 at Cornell University’s Long Island Horticultural Research & Extension Center.
NFG 2/6/19

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The Kentucky Pest News, Weekly Newsletter had a great article about pest management in high tunnel situations, mostly biological control, as many chemical control products are not labeled for high tunnel use. Here is the link: https://kentuckypestnews.wordpress.com/2018/11/06/biological-pest-management-in-kentucky-high-tunnel-greenhouse-tomato-production-systems/ .
Addressing mostly arthropod pests, these are good guidelines for disease control too:

  1. Sanitation and cultural controls in and around structures, which includes screening and weed control.
  2. Biweekly Monitoring – visual inspection of plants and sticky cards, keeping written records.
  3. Recognize pest problems early, before they are at critical levels. Properly identify pests; for some, identifying them to species. County Extension offices can help.
  4. Release beneficial species (natural enemies and pollinators) – monitor effects – consult with extension specialists. Beneficial species require management.
  5. Anticipate future problems based on previous crop history (refer to records).

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Excessive rains have led to widespread occurrence of fungal anthracnose and bacterial leaf scorch in trees, as well as other tree diseases, and resulted in lots of mushrooms and bracket fungi.  We are noticing many leaves falling early from trees such as silver maple

Silver Maple Leaf Spot

and sycamore. In disease affected trees, defoliation may be noticeable especially in low lying areas without good air circulation. At this point in the season, leaf spot and drop will have no long term effect on the health of the trees.
NFG 10/5/2018

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Conditions of wet weather and high humidity have been very favorable for boxwood blight in the Mid-Atlantic region, where states have confirmed boxwood with the serious blight.   The fungus Calonectria pseudonaviculata causes severe defoliation and death of container boxwoods, and dieback of in-ground plantings. Most boxwood species are susceptible, including American and English boxwood (Buxus sempervirens), little leaf boxwood (B. microphylla) and hybrids such as B. sinica. Pachysandra is a host, and can be a source of spores causing new infections. Sweetbox (Sarcococca) has been identified as a host. Other diseases affect boxwood, and environmental stress plays a role in predisposition to disease. Timely and accurate identification by microscopy is important for management of this aggressive disease. Sanitation is extremely important in management. Contact DE Dept of Ag or the UD Plant Diagnostic Clinic if you suspect boxwood blight.
NFG 9/28/2018

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June was a very busy month for the UD Plant Diagnostic Clinic, with 160 plant and arthropod samples logged into the data system. Of those samples, 133 or 86% were from Delaware, but 22 were from MD with 5 from VA. Most (87%) were for disease diagnosis, but there were some arthropod ID's, and some plant/weed ID's. Commercial samples through Cooperative Extension accounted for 56% of samples. Ornamental plants made up 37% of samples, with environmental stress playing a role, and Botrytis and bacterial blight showing up. Vegetable samples made up 40% of the total, and Field Crops 12%. Take all of wheat was diagnosed for the first time in a few years, and anthracnose and gray leaf spot have been seen on corn. Potato and tomato were diagnosed with early blight caused by Alternaria.

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A UD fact sheet, updated in February of 2017 gives timely info on leaf spot diseases of garden tomatoes. Fungal leaf diseases such as Septoria, bacterial leaf spot, and early blight can cause loss of leaves. Some leaf diseases such as anthracnose can lead to problems on ripening fruit. Click link below for fact sheet:
Tomato-Leaf-Spots-Fact-Sheet-Feb2017

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Pest and Beneficial Insect Walk, $15  Wednesday, June 20, 4-6 pm, University of Delaware Botanic Gardens, 531 S College Avenue, Newark.  Meet at the entrance to Fischer Greenhouse.  Learn to identify insect and disease pests, as well as beneficial insects in the landscape on a walk through the University of Delaware Botanic Gardens.  Instructors: Nancy Gregory, Brian Kunkel, and Carrie Murphy. Credits available: 2 pest, 2 ISA, and 1 CNP.  Register with Carrie Murphy (302) 831-2506 or cjmurphy@udel.edu 
NFG 6/11/18