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[1] Cucurbits - multistate
[2] Basil - northeast region

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[1] Cucurbits - multistate
Date: 4 Jul 2009
Source: Delmarva Now / The Daily Times [edited] <http://www.delmarvanow.com/article/20090704/ESN06/907040315/-1/ESN>

Cucurbit downy mildew reported in Suffolk

Cucurbit downy mildew has been reported and confirmed this week [week of 29 Jun - 3 Jul 2009] on pickling cucumbers in a Suffolk [Virginia] sentinel plot. Downy mildew has also been reported in North Carolina, Georgia, Florida, Alabama, Louisiana and Texas.

This current outbreak is an unusually early reporting of the disease this far north. Cucurbit growers are urged to consider spraying preventative applications for downy mildew and thoroughly scout for the disease. Cucumber growers in particular are strongly recommended to initiate a downy mildew protection program. Due to the location of this outbreak and persistent rainy conditions, growers near the outbreak are advised to be diligent for management of the disease.

Fungicide applications should be initiated prior to disease development and applied on a 7-10 day schedule. Cultural practices, such as avoiding low lying fields and excessive overhead irrigation, will also suppress disease development. Cucurbit downy mildew can be recognized initially by small yellow spots on the upper surface of the lower leaves. When humidity is high (particularly early in the
morning) blue/gray sporulation can be found on the underside of the leaves.

[Byline: By Bill Shockley]

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[2] Basil - northeast region
Date: 26 Jun 2009
Source: Horticulture News, Cornell University [edited]
 <http://blogs.cornell.edu/hort/2009/06/26/late-blight-a-serious-disease-killing-tomatoes-and-potatoes-this-year/>


A disease affecting gardens and farms in the northeast is a relative newcomer -- basil downy mildew. In 2008, the disease was severe on many of the region's farms. It often goes undetected because the major symptom -- leaf yellowing -- looks similar to nutrient deficiency. The downy spore-bearing structures only appear on the undersides of leaves.

[Byline: Via Meg McGrath]

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[Downy mildew caused by the fungus _Pseudoperonospora cubensis_ is a devastating disease of cucurbits and has been reported from different locations worldwide. Different pathovars with variable host preferences seem to exist, and, for example, a strain that affects cucumbers may not necessarily affect melons. By affecting the leaves and thus the photosynthetic potential of its host, downy mildew reduces yield and fruit quality, and it can eventually kill the host.
Under favourable condition, plantings can be infected so rapidly that they appear to have been frosted. The fungus survives on cultivated or wild cucurbits, and volunteer crop plants or weeds may serve as sources of inoculum.

_Peronospora lamii_ causes downy mildew on basil (_Ocimum basilicum_) and can also affect some other related species, including mints, nettles, salvia and ornamental coleus. Symptoms vary on different varieties of basil and may include chlorotis and necrosis of leaves which can result in total crop loss. The fungus has been reported from Europe and Africa, and was 1st reported in the USA in Florida in 2007.
A new, more virulent strain is suspected to have arisen in Uganda and to be responsible for the recent spread to new areas. Seed transmission is suspected as the reason for recent outbreaks in Europe.

Both pathogens are spread by wind, rain splash, mechanical means and with infected plant material. Disease management may include fungicides, phytosanitary methods to eliminate inoculum, cultural measures (for example crop rotation) and use of cultivars with low susceptibility or with resistance.

Maps
USA:
<http://www.mapsofworld.com/usa/usa-road-map-enlarge-view.html>,
<http://www.mapsofworld.com/usa/usa-state-and-capital-map.html> and
<http://healthmap.org/promed?v=40,-97.6,4>
US states:
<http://www.census.gov/geo/www/us_regdiv.pdf>

Pictures
Downy mildew on cucumber leaf:
<http://www.ag.ohio-state.edu/~vegnet/news/currentvn10-06_files/image002.jpg>
Photo galleries of downy mildew on cucurbit species:
<http://www.ces.ncsu.edu/depts/pp/cucurbit/images.php>  and <http://vegetablemdonline.ppath.cornell.edu/diagnostickeys/cucurleaf/downy/down_pump.htm>
Downy mildew symptoms on basil:
<http://www.igzev.de/images/projekte/2.3.2.jpg>,
<http://ag.udel.edu/Extension/pdc/images/Basil-DM-leaves-top.jpg>  and <http://ag.udel.edu/Extension/pdc/images/Basil-DM-leaves-under_000.jpg>
Microscopy of _P. lamii_ spores:
<http://www.ppdl.purdue.edu/PPDL/images/coleusdm5.jpg>

Links
Cucurbit downy mildew, disease information:
<http://vegetablemdonline.ppath.cornell.edu/factsheets/Cucurbits_Foliar.htm>,
<http://web.aces.uiuc.edu/vista/pdf_pubs/927.pdf>  and <http://www.avrdc.org/LC/cucurbits/downy.html>
Cucurbit downy mildew pathotypes:
<http://www.ces.ncsu.edu/depts/pp/cucurbit/thedisease.php>
Downy mildew websites of MSU:
<http://plantpathology.msu.edu/labs/hausbeck/ForGrowers.html>  and <http://www.ipm.msu.edu/downymildew.htm#17>
_P. cubensis_ taxonomy:
<http://www.indexfungorum.org/Names/SynSpecies.asp?RecordID=120276>
Downy mildew update from University of Delaware via:
<http://www.ces.ncsu.edu/depts/pp/cucurbit/>
Basil downy mildew information:
<http://vegetablemdonline.ppath.cornell.edu/newsarticles/basildowny.html>,
<http://ag.udel.edu/Extension/pdc/>,
<http://cat.inist.fr/?aModele=afficheN&cpsidt=17331838>  and
<http://www.apsnet.org/pd/searchnotes/2005/PD-89-0683C.asp>
_P. lamii_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=186550>
- Mod.DHA]