| Potato Crop Update - #7, July 21, 2003 | |
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Contents: Potato Growth and Development Update. A.J. Bussan, Vegetable Specialist, UW-Madison, Horticulture Potato Disease Update. W. R. Stevenson, Department of Plant Pathology, UW-Madison |
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Potato Crop Growth and Development Update – Alvin J. Bussan, Potato and Vegetable Production Systems Specialist, UW-Madison, Horticulture Department, 608-262-3519 or ajbussan@wisc.edu |
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We have been monitoring tuber bulking for three different Russet potato varieties Bulking increased tuber weigh by 30 to 50% from June 30 to July 9. Interestingly, each hill had a one less tuber across three different varieties over the same time span. By July 9, each Russet Burbank hill had 14 tubers/plant and a total tuber weight of 2.7 pounds/hill. In comparison, A90586-11 had 10 tubers per hill with and average weight of 2.27 pounds/hill. W1348 had 13 tubers/hill and a total tuber weight of 1.8 pounds/hill.
Chuck Kostichka at HARS is also monitoring bulking data from a number of white, red, and other Russet lines as part of the SpudPro evaluation trial. I will summarize the results of those measurements over the course of the next several weeks and some of those results will likely be shared during the upcoming field day.
In addition to monitoring tuber bulking, we have begun determining tuber set for a number of different potato lines. Of the russet types, Burbank, W1348, and W1836 have set approximately 14 tubers per plant. A90586-11 has set an average of 11 tubers/plant and Silverton and Norkotah have set 9 to 10 tubers/plant on average. Tubers represented were greater than 1 cm in diameter. Smaller or secondary tubers were also counted and will be monitored to determine their fate.
Round white lines set tuber numbers similar to Russet Burbank. Atlantic and W1201 have set an average of 10 to 12 tubers in our trial. One exception has been W1355 which set 20 tubers greater than 1 cm in diameter and an additional 20 secondary tubers. We will dig red potato lines next week and be able to report the tuber set then.
Growers need to monitor precipitation and rainfall closely over the next several weeks to insure good water management. Precipitation has been spotty and variable across different parts of the state. Potato crop looks good and to maintain current momentum in growth drought stress should be minimized. As I stated last week, at this point drought stress can have the greatest effect on quality.
Potato harvest is also continuing across a number of different farms. I would like to hear about any quality concerns with different potato crops as they are being harvested so please feel free to contact me. See you Tuesday or Wednesday at the upcoming field days. |
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Important
dates to remember:
July 22 Hancock
Ag Research Station Field Day ( July 23 Antigo
Field Day (
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| Vegetable Disease Update - W. R. Stevenson, Department of Plant Pathology, UW-Madison, Tel. No. 608-262-6291, Email: wrs@plantpath.wisc.edu | |
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Potatoes There are no reports of late blight (photos) in Wisconsin as of today. Conditions in the southern half of the state continue to be favorable for late blight development as evidenced by the continued increase in severity values over the past week. Northern Wisconsin however is very dry and conditions are much less conducive to disease development in these areas. Canopies are dense in most fields and the foliage remains wet for extended periods after irrigation and rainfall. Growers should remain alert for the early symptoms of late blight since there is still a long way to go before vinekill. Most growers are treating their fields every 7 to 10 days as a preventative measure for foliar disease control.
Early blight (photos) continues to progress a bit more rapidly than last year and what would be considered a normal year. Most growers I’ve talked with indicate that the crop is about a week ahead of normal in maturity. Given that early blight susceptibility increases as the vines mature, the level of early blight on this calendar date is anticipated. Continued use of protectant sprays will help to slow disease development.
Last week I reported that some growers were experiencing white mold in a few production fields. During the past week, the growers I’ve talked with indicate that bacterial stem rot is now appearing on fields where vines have been kept continuously wet with irrigation and rainfall during the past few weeks. Vines at the base of the dense canopy are soft, mushy and often have a foul odor. This is nothing new, but it is cause for a reminder that vines need to dry between irrigations if at all possible. Keeping the leaves and stems bathed in a film of water day after day, week after week, is conducive to a buildup of soft rotting bacteria that find their way into wounds on the stem and leaves. Copper sprays at this point are probably pointless for control. Careful irrigation that matches crop needs to the water applied would appear to be the most reasonable approach to managing this disease problem.
Carrots Alternaria and Cercospora leaf blights continue to progress on the most susceptible cultivars. Protective sprays with chlorothalonil or chlorothalonil alternated with a strobilurin fungicide such as Quadris or Cabrio are effective control measures. We have extensive trials out in the state this year looking at how disease forecasting programs combined with pest scouting and cultivar susceptibility can affect overall disease control efficacy and the economics of production. Small field plot research at the Hancock Ag Research Station during the past two years demonstrated the usefulness of this approach on carrots. We are now taking this to the next level on grower commercial acreage. Results so far are promising.
Processing Beans The presence of white mold on potatoes is a good reminder to processors and growers that conditions are also favorable for white mold infection on processing beans (photos). The most susceptible stage of crop development is the period of open bloom. Careful irrigation from bud stage through the bloom period can reduce the risk of this disease. Fungicide sprays, if applied, should be used during the bloom period for best control of white mold. As we look at weather forecasts for the week ahead, the forecasted cool weather combined with rain at the beginning and end of the week would appear to be highly favorable for the development of white mold, especially on those fields with a history of the disease. Careful attention should be given to management of white mold in the week ahead. Also, a gentle reminder that there is a biological control measure available, Intercept, for the management of white mold. This material needs to be applied prior to planting and ideally the fall ahead of planting a field with a white mold susceptible crop and immediately disked into the field. The fungus in this biocontrol tool will attack and rot the sclerotia of the white mold fungus, thus reducing the primary inoculum. Measures such as these combined with careful irrigation and crop rotation can make a big difference in the management of white mold.
Hancock Field Day – July 22 beginning at 9 am Antigo Field Day – July 23 beginning at 1 pm at the airport See you there! Specimens for diagnosis are always welcome. |
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Current P-Day and Severity Value Accumulations for 2003 (http://www.plantpath.wisc.edu/wivegdis/index.htm)
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Location |
Calculation Date: |
P-Day Total |
Severity Value Total |
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Antigo emerging June 4 |
7/20 |
336 |
26 |
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Antigo emerging June 14 |
7/20 |
265 |
8 |
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Antigo emerging June 24 |
7/20 |
194 |
8 |
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Grand Marsh emerging 5/19 |
7/20 |
437 |
37 |
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Grand Marsh emerging 5/24 |
7/20 |
413 |
37 |
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Grand Marsh emerging 5/28 |
7/20 |
391 |
37 |
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Hancock emerging 5/13 |
7/20 |
485 |
25 |
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Hancock emerging 5/17 |
7/20 |
461 |
25 |
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Hancock emerging 5/25 |
7/20 |
415 |
23 |
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Plover emerging 5/13 |
7/20 |
478 |
12 |
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Plover emerging 5/24 |
7/20 |
418 |
12 |
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Plover emerging 6/3 |
7/20 |
355 |
12 |