Author: minter.21

Cucurbit Downy Mildew Reports Intensifying

Following initial detection in Medina County the first week of July, additional confirmations of this pathogen have been made from fields in Wayne, Seneca, and Huron counties, as well as the OSU Extension seminal plot in Wooster. Laboratory diagnosis was conducted by the C. Wayne Ellett Plant and Pest Diagnostic Clinic at the OSU CFAES Wooster Campus. Monitoring continues at OSU sentinel plots in Fremont, Celeryville, and Piketon, with no confirmed detections at the time of writing. Additionally, symptoms consistent with bacterial spot, yellow-vine decline, and bacterial wilt have been observed in the sentinel and nearby plots at OSU research stations across the state, so diligence in insect and disease scouting and management remains imperative.

 

 

 

 

Heavy sporulation on the underside of a cucumber leaf in Wayne county Sentinel plot F. Rotondo.

 

 

 

 

 

 

 

 

Visual foliar symptoms on the upper surface of cucumber leaves from Huron (left) and Wayne (right) counties, F. Rotondo

 

 

 

 

 

 

 

Microscope view of Cucurbit Downy Mildew, where the individual, lemon-shaped, sporangia can be observed along with sporangiophores, F. Rotondo.

The following information appeared in this newsletter on July 2nd but remains relevant and is reposted for reader convenience.

Growers who have cucumbers and cantaloupe in their fields should take quick action to protect their crop. Cucurbit Downy Mildew is best managed with preventative applications before infection takes place. Once visual symptoms appear, control becomes increasingly difficult and yield reductions may occur. In conditions favorable for disease development, and without effective and timely management, Cucurbit Downy Mildew can cause rapid decline of the plant, severe defoliation and ultimately plant death in just the matter of days. Disease development is favored by rainy, humid conditions (relative humidity greater than 85%) and cooler temperatures ( 60°F to 70°F)

According to research trials completed in Ohio, Michigan, and other states and provinces around the Great Lakes region, the best fungicide options are as follows: Orondis Opti (FRAC 49+M05), Ranman (FRAC 21), Omega (FRAC 29), Previcur Flex (FRAC 28), and Elumin (FRAC 22). These should be tank mixed with chlorothalanil (Bravo, Equus, etc.) or mancozeb (Dithane, Manzate, etc.). Orondis Opti is a premix already containing chlorothalanil, but at a reduced rate.  Fungicides have restrictions on how much product can be applied and how often, so follow the label, the label is the law. The more effective fungicides should be rotated to avoid resistance development in the pathogen.

Growers in Ohio should also intensify scouting of cucumbers and melons. Look for yellow or tan angular lesions delimited by veins on the top surface of leaves, and fuzzy grey/brown growth on the undersides of the lesions. With a good hand lens or a smartphone camera with high magnification you may be able to see small dark brown/purple spots within the fuzzy growth. These are the spores of the downy mildew pathogen. You can also utilize the Cucurbit Downy Mildew IPM Pipeline website, where you can sign up for alerts notifying you of nearby confirmed Cucurbit Downy Mildew observations.

If you suspect downy mildew in cucumber or melon please submit samples to the C. Wayne Ellett Plant and Pest Diagnostic Clinic (CWE-PPDC) for confirmation. Instructions for sample submission are here. Please contact Dr. Francesca Rotondo at 330-263-3721 or rotondo.11@osu.edu with any questions. You can also work with your county extension educator to get samples submitted to the lab. A major ‘thank you’ to Dr. Rotondo and her staff in the Plant and Pest Diagnostic Clinic for their critically important work! Also, thanks to financial support from the Ohio Produce Growers and Marketers Association’s Ohio Vegetable and Small Fruit Research and Development Program, there is no fee for this service for Ohio vegetable growers. Please find additional information on Cucurbit Downy Mildew here from OSU and Michigan State

Worsening Drought Conditions Across Southern Ohio

Author: Aaron Wilson

Summary

As I write this article on Monday afternoon, showers and a few embedded storms are rolling across the Buckeye State. However, for southern and southeastern Ohio, this has largely not been the case for the last several weeks. Precipitation over the past 30-to-60-days is running 25-75% of normal, with some parts of Pickaway, Ross, Noble, Morgan, Washington, Monroe, and Belmont Counties receiving less than 2 inches over this period (Figure 1). As a result, the latest US Drought Monitor depicts about 8% of Ohio in D2-Severe Drought and abnormally dry conditions or worse being felt by

approximately 70% of the state. This has led to notable crop stress on drier ground, deep cracks in the ground from the lack of soil moisture, poor pasture conditions, and short-cuttings of hay. Producers are encouraged to provide observations from their locations by submitting a Condition 

Monitoring Observer Report (go.osu.edu/drought_cm

or). For more information and resources, please visit our Drought Conditions and Resources Knowledge Exchange page or visit the State Climate Office of Ohio.

 

 

 

 

 

 

Weather Forecast

Scattered showers and storms are possible on Tuesday through Thursday this week, before high pressure and drier air moves in for the weekend. However, widespread heavy rain is not expected. The Weather Prediction Center is currently forecasting 0.01-0.50” for the state over the next 7 days (Figure 2), though locally heavier amounts are possible. Temperatures will generally rise into the low to mid 80s each day with overnight lows in the 60s, about average for mid to late July.

The 8-14 day outlook from the Climate Prediction Center and the 16-Day Rainfall Outlook from NOAA/NWS/Ohio River Forecast Center show temperatures are likely to be above average with precipitation probability leaning toward wetter than average (Figure 3). Climate averages include a high-temperature range of 83-86°F, a low-temperature range of 60-66°F, and weekly total precipitation of 0.90-1.20”.