Pest News June 1, 2012

Though this week's NC Pest News does not contain anything specifically about vegetable or fruit pests (though kudzu bugs may be a problem for folks growing edamame), I did want to draw your attention to some possible issues to be on the lookout for.

Cucurbit downy mildew and late blight of potato and tomato are very devastating and rapid moving diseases.  Though we do not have any reports of these diseases in WNC or our immediate surrounding areas, they have been reported in other parts of NC.  Weather has been ideal for both of these diseases in our area, cool and wet.  Also, because weather has been unsettled (many storms moving throughout the east coast) there is a chance that the spores of these pathogens could travel to WNC.

In fact, the Cucurbit Downy Mildew Forecasting site issued WNC a low risk warning on Friday.  Cucurbit downy mildew has both been detected in eastern and central NC.  On June 1, new reports of the disease were confirmed as close as Franklin, Nash and Wake Counties in NC.  Cucurbit downy mildew is also tracking up the east coast into New Jersey.  To view a map of current Cucurbit Downy Mildew outbreaks visit the CDM IPM Pipe website.  Growers are advised to scout for this disease and to report to their local cooperative extension office if they need assistance or to report an outbreak. 

 

Symptoms of cucurbit downy mildew on cucumber are angular lesions that start a pale green and progress to bright yellow and then finally brown (above).  The best way to identify cucurbit downy mildew is to turn the leaf over to look for the downy growth of the pathogen's spores (below). 

 

Late blight on potatoes has also been detected in Camden County, NC and various other states on the east coast.  To view a current map of these outbreaks, visit the USABlight website.  Growers are urged to scout for this disease as well, as we know this can be a deal breaker for organic producers especially.

 

Late blight on a tomato leaf.

  Again, these diseases have not been reported in WNC.  If you suspect you have these diseases in your planting, please contact your local Cooperative Extension office for assistance.  It is reporting and early detection that can save a planting!

New Rust Found on Eggplant in Florida

It seems like this year will be challenging for pest control on vegetables. Please see the message below from Gene McAvoy, County Extension Director in Hendry County, FL.

Dr Pam Roberts reports a new find of rust on eggplant in SW Florida.

Rust detected on eggplant (Solanum melongena) in Southwest Florida Pamela D. Roberts, Katherine Hendricks, and Mark Verbeck 3/3/2012

Lesions were detected on the top of eggplant leaves that were roughly circular, with a yellow halo and a dark center. Lesions on the undersides of the leaves were similar except they were a bit smaller and contained pustule, cup-like structure with erupting yellow to orange spores.

Microscopic examination revealed that the individual structures (aecia) contained spores (aeciospores). Spores were red-orange in color and round to ovoid.

A rust disease caused by Puccinia sp. was described on eggplant in Georgia in 1997. Eggplant was the aecial host for the rust pathogen of pearl millet (Pennisetum glaucum). We suspect this is the same rust and will follow with additional testing.

In this outbreak, nearly every eggplant in a 10 acre field was affected. Plants are mature and have been harvested 2 to 3 times. No symptoms occurred on fruit.

To see pictures of the disease and read more about, please visit Eggplant Rust Alert.

Downy Mildew Confirmed in Buncombe County

Downy mildew has been confirmed at very low levels in a 2-acre cucumber field in Buncombe County. Growers are encouraged to begin treatment.

Review this post from June on the current recommendations: Pest News June 24

Don't forget to review the Cucurbit Downy Mildew Forecasting website for more information.

Spotted Wing Drosophila Alert July 17

On June 29 I posted on the threat of a new pest, the spotted wing drosophila (SWD). This post is on the latest development of SWD in NC from Dr. Hannah Burrack.

Spotted Wing Drosophila Alert
For commercial fruit growers

Suspected spotted wing drosophila (SWD, Drosophila suzkii) larvae have been found in North Carolina grown caneberries. Growers in areas with a known history of SWD should undertake an aggressive management program for this potentially devastating pest. Growers in areas without a history of SWD should determine the status of SWD on their farm by sampling fruit and trapping adult flies.

SWD in North Carolina

SWD has been detected in the following 23 North Carolina counties:
Anson, Ashe, Burke, Bladen, Craven, Davidson, Edgecombe, Greene, Henderson, Johnston, Lee, Lenoir, Lincoln, Montgomery, New Hanover, Onslow, Pender, Person, Randolph, Rowan, Sampson, Wake and Wayne.

SWD larvae have been found in fruit in the counties indicated in bold. In all of the listed counteis, adult SWD have been captured in traps.

SWD can feed on blueberries, blackberries, raspberries, strawberries, grapes figs, peaches, cherries, and many other soft skinned fruits, both cultivated and wild.

Growers of these crops in and around the 22 counties where SWD has been detected should consider themselves to be in areas witha history of SWD and manage accordingly.

SWD Management

Because SWD is new to North Carolina, our current management strategy relies on insecticides. You can find lists of registered insecticides and their probable efficacy against SWD at www.ncsmallfruitsipm.blogspot.com.

Select insecticides that will be effective against SWD (those expected to provide "excellent" control), and apply insecticides at the high end of the labeled rate range. Apply insecticides every 7 days, ideally rotating between at least two insecticides with different modes of actions (MOAs).

Always observe proper preharvest intervals and be aware that many insecticides have maximum residue levels (MRLs) for the United States and other countries. These residue levels may potentially occur before the maximum number of allowable insectice applications per season is reached. USDA maintains a database of MRLs (http://www.mrldatabase.com/).

Check with your marketer or wholesaler before using a new insecticide on your crop to ensure that it is acceptable in all locations where your fruit may be sold.

SWD larvae take 7-10 days to mature, so larvae found in fruit now are the result of egg laying activity over 1 week prior. Larvae inside fruit cannot be controlled; only adult SWD can be killed with insecticides.

Sanitation is crucial for SWD management. All ripe fruit (marketable or not) must be removed from the field and disposed of. Culls should not be left on the ground or plant. Freezing or "baking" in clear plastic bags placed in the sun will kill larvae, Burying or composting may not.