Johnston County Tobacco News

Frogeye Leaf Spot

This is information that Norman Harrell, Wilson County Tobacco Extension Agent, prepared and it is also right on target for Johnston County:

2018 has been another challenging and trying year. The majority of growers are 2 - 4 weeks behind where they normally would be at this time of year. The crop is late and it needs to hold as long as possible. In the last 30 days, Wilson County has received over 12" of rain, which has brought it's on set of challenges with too much water. There is a fair amount of Granville wilt in the county. High rainfall and high humidity has created some issues with leaf diseases. Below are some observations.

1. Frogeye leaf spot (pictured above) is caused by the pathogen Cercospora. Frogeyeleaf spot lesions are about the size of a pencil eraser and brown to tan in color. In the center of the lesions there will be small black dots that are composed of masses of spores. As lesions get older, the center will fall out. As the leaf gets more lesions, the leaf will begin to degrade.

An application of Quadris fungicide (Azoxystrobin) will protect healthy leaf tissue for 2 weeks or more from frogeye leaf spot. If you make an application, coverage is important. I would apply with hollow cone nozzles at high pressure and plenty of water. Applications of Quadris near harvest are not necessary or advised, but Quadris has 0 day preharvest interval (PHI).

2. Brown spot is caused by (Alternaria). Brown spot is an opportunistic disease that affects plant tissue that is already in decline for one reason or another. Therefore, leaves that are thinner than normal, affected by sunlight, or affected by other pathogens like target spot are more susceptible.

Alternaria on tobacco is not listed as a target disease that is controlled on the Quadris label. Alternaria spp. is listed in other crops on the Quadris label. This means there could be some benefit of preventing/minimizing Brown Spot if you are making an application for Frogeye leaf spot.

3. Flea beetles are also widespread in tobacco. Threshold is 60 or more beetles per plant. Control options include Admire Pro (imidacloprid) and Orthene (acephate). Admire Pro has a 14-day PHI and Orthene has a 3-day PHI. Be sure to be aware of possible restrictions with these pesticides with your contracting company.

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Disclaimer agrichemicals:

Recommendations for the use of agricultural chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by North Carolina Cooperative Extension nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any chemical. For assistance, contact your county Cooperative Extension agent.