Cucurbit Downy Mildew Epidemic Updates for 2008

July 2, 2008
New reports from eastern SC - commercial field in Williamsburg County and sentinel plot in Sumter County. A 45-acre commercial field of cucumbers in Williamsburg County, SC (near Barrineau Crossroads) is showing 15% disease incidence. Early plantings in this field were stressed from heat and dryness; late plantings have been hit with CDM. Symptoms are estimated to have appeared at the end of June. Nearby to the west in Sumter County, SC is a sentinel plot, where 15% incidence was observed on Straight Eight cucumber yesterday afternoon. Severity is around 15%, with about 1% necrosis. Symptoms appeared during the last week of June. Our thanks to Tony Keinath for these reports.

June 30, 2008
Updates on the epidemic situations near Charleston, SC and Tifton, GA. At the Tifton sentinel plot ... light infections of very recent origin were reported on Straight Eight cucumber and Waltham Butternut squash. Other varieties were checked with no disease present. At Charleston, SC ... Poinsett 76 cucumbers at the sentinel plot are showing 20% incidence, 20% severity, 0.5% necrosis, and abundant sporulation. Symptoms were new. A home garden infection on James Island was also reported, where about 3/4 of an extremely small planting of Straight Eight cucumber is affected. Our thanks to David Langston and Tony Keinath for these reports.

June 27, 2008
No new outbreaks or updates to report.

June 25 2008
Downy mildew has been discovered in Toombs County, GA. Disease was reported late Monday in the sentinel plots near Reidsville, GA. Symptoms are fresh, with about 10% incidence in the plot. Disease is on Waltham Butternut Squash and Straight Eight Cucumber, with the squash showing much greater severity than the cucumber. Our thanks to David Langston for this report.

June 23, 2008
First report from southern Canada in 2008; update from LA. Downy Mildew was reported late Friday, June 20, on cucumber in Elgin County, Ontario, Canada, near the town of Alymer. Approximately 10% of a 5-acre commercial field is symptomatic. First symptoms are estimated to have appeared around June 16/17. This source will join the forecast rotation immediately. Our thanks to Elaine Roddy for this report. In LA ... in the commercial field next to the sentinel plot in Vernon Parish, where last Friday (June 20) we reported CDM on watermelon, CDM was confirmed late last week on cantaloupe. About 1% of a 1-acre planting is infected. As with the other LA finds described June 20, first symptoms are estimated to have appeared around June 12. Our thanks to Don Ferrin for this update.

June 20, 2008
Three new sources have been reported in the last 2 days. These are from sentinel plots in Gadsden County, FL and Charleston County, SC (first report from SC), plus discoveries in a sentinel plot and adjacent commercial field in Vernon Parish, LA (first report from LA). The Gadsden County, FL find is on Waltham Butternut Squash, where about 5% of the plot is infected. The LA finds are on cantaloupe and cucumber in the sentinel plot. Lesions were not observed last week but are now present. The sentinel plot is adjacent to a commercial field, where downy mildew is present on watermelon. Disease was observed in a lower portion of the field and is estimated to have been active for at least one week. The SC outbreak is on Straight Eight cucumber. No symptoms were evident just two days ago but as of this morning heavy sporulation was observed on a few leaves. Our thanks to Amanda Gevens and Stephen Olson (Florida), Don Ferrin (Louisiana), and Tony Keinath (SC) for these reports.

June 18 2008
Downy mildew has been discovered in Tift County, GA. Disease was reported yesterday in research plots near the town of Tifton. Approximately 2% of an 8-acre planting is infected. Symptoms have appeared within the past several days. Our thanks to Keisha Hadden for this report.

June 16 2008
Downy mildew has been discovered in St. Johns County, FL. Downy mildew was confirmed and reported late last Friday in a sentinel plot in Hastings, FL. About 20% of a 400 sq. ft. plot is infected. Symptoms are estimated to have first appeared near June 6. Our thanks to Amamda Gevens for this report.

June 13, 2008
No new outbreaks or updates to report.

June 11, 2008
No new outbreaks or updates to report.

June 9, 2008
No new outbreaks or updates to report.

June 6, 2008
No new outbreaks or updates to report.

June 4, 2008
Downy mildew has been discovered in Brooks County, GA. Downy mildew was observed Tuesday, June 3 in a commercial pickling cucumber field near the town of Morven. Of many fields checked, only one showed any symptoms and these appeared very recently. Disease incidence was only about 0.5% of a 20 acre field. Our thanks to Phil Denlinger and David Langston in GA for this report.

June 2, 2008
Downy mildew has been discovered in Harris County, TX. Downy mildew was confirmed late Friday, May 30 via samples taken from a commercial planting near the town of Hockley. A watermelon field of 10 acres showed about 1% disease incidence. First symptoms likely appeared near May 23. Our thanks to Tom Isakeit in TX for this report.

May 30, 2008
No new outbreaks or updates to report.

May 28, 2008
Update on the disease situation in southeast FL. The following disease report was received this morning from Dr. Ken Pernezny. Contrary to earlier indications in this space, the discovery reported on May 19 was NOT in Palm Beach County near Belle Glade; rather, it was near Ft. Pierce in St. Lucie County. We hope this has not caused anyone undue confusion. Our thanks to Dr. Pernezny for this richly detailed report.

Outbreak details and the full narrative description:

Downy mildew was discovered earlier this Spring on Winter Squash (Sweet Dumpling) in St. Lucie County, FL in a research plot near the town of Ft. Pierce. Disease incidence was about 50% in this plot approximately .25 acres in size. First symptoms appeared near April 16.

Control Products Used (results):

• Bravo Ultrex + Manzate75 DF a/w Pristine38 WG + Forum 4.18 F (good)
• Previcur Energy 840 SL (good)
• Previcur Flex 720 SL + Manzate 75 D (best)
• Revus 2.08 F protocol 1 and Revus 2.08 F protocol 2 (very good)

Narrative:

All treatments reduced downy mildew below that in the untreated control, some as much as 75%. The two Revus-based protocols and weekly applications of Previcur Flex + Manzate 75 DF were particularly effective. Disease control was correlated with increased yield; weigh of marketable fruit was up to 1.5 times higher where effetive fungicides were sprayed. Symptoms of phytotoxicity were not observed for any of the treatments.

Downy mildew pressure was extremely severe in this experiment. Plants in control plots and in border rows were dead by harvest time. The first appearance of disease was also quite early (~April 2). Two 2-in rain events occurred in the Ft. Pierce area in March, normally one of our driest months. These episodes of precipitation probably were responsible in part for the early and substantial disease development.

May 26, 2008
No new outbreaks or updates to report.

May 23, 2008
No new outbreaks or updates to report.

May 21, 2008
Update on the disease situation in Marion County, FL. New downy midlew lesions were discovered on 3 more cucurbits at the sentinel plot near Citra on Monday: Poinsett 76, Jumbo, and Straight 8. The Straight 8 symptoms were greatest, with disease incidence of 10% and severity of >60% on some leaves. The other infections were quite minor, consisting of <5% incidence and limited sporulation. Our thanks for Amanda Gevens in FL for this report.

May 19, 2008
*** May 28 update: This source was NOT near Belle Glade as originally indicated; it was in St. Lucie County near the town of Ft. Pierce. Please refer to the complete description in the May 28 installment. *** Downy mildew has been reported near the town of Belle Glade in Palm Beach County, FL. Very little is known about this particular source, other than that it has apparently existed since mid-April. There have been other reports in Palm Beach County since early this growing season. We will relate any details we receive about this source as we get them. This location will be combined with the other known sources in southeast FL for purposes of the forecasts.

May 16, 2008
Downy mildew has been discovered in Marion County, FL. Downy mildew was confirmed on Thursday, May 15 on Waltham Butternut squash during a regular inspection of the sentinel plot near Citra, FL in northern Marion County. No other cucurbits in this plot nor in the Citra area show any symptoms at this time. The 200 sq. ft. sentinel plot is approximately 5% infected. Our thanks for Amanda Gevens in FL for this report.

May 14, 2008
No new outbreaks or updates to report.

May 12, 2008
No new outbreaks or updates to report.

May 9, 2008
No new outbreaks or updates to report.

May 7, 2008
No new outbreaks or updates to report.

May 5, 2008
Downy Mildew has been discovered in Orange County, FL. Disease was confirmed in a sentinel plot near Apopka on cantaloupe (Cucumis melo). Disease incidence is very low, lesions on a few leaves, with no other lesions observed on remaining plants in that row or on other rows. These appear to be primary lesions. Disease symptoms were evident under the microscrope. Our thanks to Jeff Kaesberg for this report.

May 2, 2008
No new outbreaks or updates to report.

April 30, 2008
No new outbreaks or updates to report.

April 28, 2008
No new outbreaks or updates to report.

April 25, 2008
Sentinel plot update from southwest FL (Immokalee). A follow-up to the April 14 disease update (from Gary Taurick via April 24 email to Gerald Holmes) ... Around April 14 downy mildew began appearing on plant varieties that had not been previously shown symptoms, including Poinsett 76 and Marketer. As of April 24, Poinsett 76 was rated 3 and Marketer a 2 (0=dead, 1=severe, 5=no symptoms). This 1500 sq. ft. plot is located about 6.8 miles south on Immokalee. Our thanks to Gary Taurick and Tim O'Rourke (HM station manager) for this report.

April 23, 2008
Sentinel plot update from southwest FL (Immokalee). Downy mildew was reported on Waltham Butternut squash (Cucurbita moschata) and Micky Lee watermelon (Citrullus lanatus) earlier this week. Less than 1% disease incidence was observed. Symptoms were estimated to have first appeared on or about last Wednesday, April 15. Our thanks to Pam Roberts for this report.

April 21, 2008
No new outbreaks or updates to report.

April 18, 2008
Downy mildew has been discovered in an IPM PIPE sentinel plot in Hillsborough County, FL. The sentinel plot is located near the town of Balm in the southeast portion of the county. First symptoms are estimated to have appeared on April 12. Crops affected are Cucumis sativus 'straight eight' (<1% incidence) and Cucurbita maxima 'Big Max' (~5% incidence). Our thanks to Gary Vallad for this report.

April 16, 2008
No new outbreaks or updates to report.

April 14, 2008
Sentinel plot update from southwest FL (from Gary Taurick via Gerald Holmes - 11 APR email - edited): Downy mildew plots in Immokalee were visited recently. Straight 8, National Pickle, and SMR 58 were heavily infected; much yellowing and necrosis of older leaves and typical downy mildew appearance. However, Poinsett 76 and Sumter showed almost no symptoms.

The trial was planted in early February and allowed to become naturally infected with no fungicides applied. DM lesions appeared when the plants were small. The plants are now well into the fruit-setting stage. Our thanks to Gary Taurick for this update.

April 11, 2008
No new outbreaks or updates to report.

April 9, 2008
The latest update from southern FL reads the same as the last one did in mid-March. Disease is still active on squash and/or cucumber in various locales in southern FL.

April 7, 2008
No new outbreaks or updates to report.

April 4, 2008
No new outbreaks or updates to report.

April 2, 2008
The first report of downy mildew in an ipmPIPE sentinel plot arrived during the afternoon of March 31, 2008. Primary lesions were observed on leaves of acorn squash in the sentinel plot just west of Homestead, FL. Incidence and severity are very low at this time. Our thanks to Dr. Shouan Zhang for this report.

March 31, 2008
No new outbreaks or updates to report.

March 28, 2008
No new outbreaks or updates to report.

March 26, 2008
No new outbreaks or updates to report.

March 24, 2008
No new outbreaks or updates to report.

March 21, 2008
No new outbreaks or updates to report.

March 19, 2008
The mid-month update from Gene McAvoy in FL indicates that the situation remains essentially unchanged from the update earlier this month. Producers around southwest FL report that downy mildew continues to be a major problem in squash and especially cucumbers. East Coast growers and scouts indicate the downy mildew is still causing problems on cucumber. Downy mildew is still active in squash in the Homestead area.

March 5 - 17, 2008
No new outbreaks or updates to report.

March 3, 2008
Reports from southern FL indicate that downy mildew is a major problem in squash and especially cucumber in the southwest areas (Collier County). Disease is also present along the southeastern sections (Palm Beach and Dade Counties). Disease is affecting squash near the Homestead area. Cucurbits, especially cucumbers, are experiencing disease farther northward.