Recent reports bring to mind that warm and wet spring weather is perfect for development of the bacterial disease known as fireblight in susceptible hosts. Fireblight is caused by Erwinia amylovora, a bacterium that only affects plants in the rose family (Rosaceae). Some common hosts include apple, crabapple, cotoneaster, hawthorn, mountain ash, pyracantha, and pear.
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Archives for May 2013
May 28, 2013 Ann Gould
Fireblight in Ornamental Rosaceae
May 28, 2013 Joe Ingerson-Mahar
Pepper Weevil Alert #2
There are now 6 non-farm locations where adult pepper weevils are being trapped. Traps at 3 farm sites have also caught weevils in the past week, including 2 pepper fields. Large numbers of weevils are being trapped at one of these non-farm sites, 54 in a 4 day period. It is not clear if this represents typical numbers or if this year the number of weevils is exceptional.
May 28, 2013 A.Wyenandt, W.Kline, and J.Ingerson-Mahar
Potato Disease Forecasting Report 5-28-13
Potato Disease Forecasting Report 5-28-13 – Click to Download
We will be tracking DSVs for Late blight development and calculating P-days for initiating the first early blight fungicide application.
The first late blight fungicide application is recommended once 18 DSVs accumulate from green row. Green row typically occurs around the first week in May in southern New Jersey. An early season application of a protectant fungicide such as mancozeb (Dithane, Manzate, Penncozeb) or Bravo (chlorothalonil) as soon the field is accessible is suggested. Please be vigilant and keep a look out for suspect late blight infections on young plants. No late blight has been reported in our region to date.
Remember the threshold for P-days is 300! Once 300 P-days is reached for your location early blight fungicide applications should be initiated. Growers who are interested in using this model should chose the location above that is closest in proximity to their farming operation and should regularly check the Cornell NEWA website (http://newa.cornell.edu/) where this information is compiled from. Click on Pests Forecasts from the menu, select your weather station, and click on tomato diseases, set accumulation start date and a table of daily and total DSVs will be generated.
May 24, 2013 Administrator
Red Thread Disease is Active
By Jim Murphy
Several weeks ago the cool wet weather brought on some red thread disease activity that has increased over the past 4 to 5 days. Turfs under low maintenance, particularly low nitrogen fertility, have been the areas with the greatest amount of red thread. This disease has been active on on slender and strong creeping red fescues, Chewings fescue, velvet bentgrass, perennial ryegrass, and tall fescue this spring. [Read more…]
May 24, 2013 Mark VanGessel
Postemergence Sprays for Corn Fields with Palmer Amaranth
Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
I have seen Palmer amaranth seedlings emerging in corn fields that had no preemergence herbicides applied.
There are Palmer amaranth plants in DE and MD that are resistant to glyphosate. So fields with Palmer amaranth present, or fields where you suspect it is present, need to be treated with an effective herbicide (or herbicide combination) that will provide postemergence control as well as residual control. Some considerations include atrazine, Callisto, Capreno, Impact, Permit Plus, Halex, Realm Q, Resolve Q. Other products such as Status or Liberty provide effective postemergence control, but will not provide residual control.
Palmer amaranth plants look very similar to smooth and redroot pigweed. However, Palmer amaranth leaves, stems, and petioles do not have hairs (smooth and redroot pigweed do have fine hairs). Palmer amaranth’s leaves have long petioles that are often as long, or longer, than the leaf blade. As a result, the leaves often droop. Occasionally, leaves will have a variegated “V” mark or watermark across the leaf blade. On-line photos can be found at http://extension.udel.edu/ag/files/2013/05/AMAPA_images_lg.pdf
May 24, 2013 Administrator
Crabgrass is Emerging
By Jim Murphy
Very small first and second leaves of emerging crabgrass can be seen now in open turf areas.
During the last couple weeks, we have seen crabgrass emerging from open turf areas that were previously infested with crabgrass. Crabgrass emergence will probably occur later than this on better maintained turfs with a dense canopy.
