Andy Wyenandt

This is an archive of Dr. Wyenandt's posts on the Plant and Pest Advisory.

July 3, 2015

Vegetable Disease Briefs – Cucurbit downy mildew ALERT – 7/3/15

Cucurbit downy mildew was reported on watermelon in Dorchester County, Maryland and Sussex County, DE on 7/2.

This is the first report of cucurbit downy mildew in the region to date.  The most recent reports of cucurbit downy mildew on the east coast have been in cucumber and watermelon. There are at least 5 or 6 reported races of downy mildew on cucurbit in the US with each affecting a different set of cucurbit hosts. Unfortunately, very little is known about what races may be present in our region.

All cucurbit growers need to scout on a daily basis and consider adding a downy mildew specific fungicide to their regular maintenance programs. To track the progress of CDM in the US please visit http://cdm.ipmpipe.org/. For more information on the control of cucurbit downy mildew please see the 2015 Commercial Vegetable Production Guide.

Filed Under: Vegetable Crops Tagged With:
June 28, 2015

Phytophthora Control During Wet Weather

Most of New Jersey has been plagued by heavy rains and pop-up thunderstorms these past few weeks making conditions ideal for pathogens such as Phytophthora blight (P. capsici) on pepper, eggplant, tomato, and cucurbit crops. Unfortunately, Phytophthora blight can be found on most farms in the southern part of the state. Poor crop rotations with susceptible hosts only make matters worse. The pathogen has an increasing host range that also includes snap and lima beans, and all crops, other than a few resistant bell pepper cultivars, lack any resistance to the pathogen. [Read more…]

Filed Under: Organic Production, Vegetable Crops Tagged With:
June 28, 2015

Preparing for Pepper Anthracnose

Heavy rain and wind can cause pepper anthracnose to flare up quickly!

Growers with peppers in fields with a history of pepper anthracnose should scout on a daily basis and initiate a fungicide program as soon as small fruit begin to develop. Pepper anthracnose can be very difficult to control once established. All bell and non-bell peppers are susceptible. Strip picking and removing all fruit from ‘hot spots’ when they first appear may help suppress spread of the pathogen.

Preventative fungicide applications should begin at flowering or fruit set. Use a heavy volume of water and make sure coverage is extremely good. Apply high rates of chlorothalonil or Manzate weekly and tank mix and/or rotate weekly with one of the following FRAC group 11 fungicides: Priaxor (fluxapyroxad + pyraclostrobin, 11), Quadris (azoxystrobin, 11), or Cabrio (pyracolostrobin, 11).
Please see the 2015 New Jersey Commercial Vegetable Production Recommendations Guide for more information.

Mature bell pepper fruit infected by pepper anthracnose. (Each spot is the result of a single spore landing on the fruit causing an infection. The pinkish-orange masses developing in the centers of lesions are millions upon millions of spores that will be splashed via rain and wind resulting in new infections.)

Mature bell pepper fruit infected by pepper anthracnose.

Anthracnose on Mature Bell Pepper Fruit: Each spot is the result of a single spore landing on the fruit causing an infection. The pinkish-orange masses developing in the centers of lesions are millions upon millions of spores that will be splashed via rain and wind resulting in new infections.

Filed Under: Vegetable Crops Tagged With:
June 28, 2015

Vegetable Disease Briefs – 6/28/15

  • Phytophthora blight on pepper and cucurbit crops have been reported. The heavy rains that have been around lately have been ideal for P. capsici development. All growers need to scout on a regular basis and applied preventative fungicides on a regular basis as well as remain proactive by removing infected plants from field, making sure water is able to drain away from beds/fields, and cutting plastic to help dry out beds.
  • A new, more aggressive form of Black leg has been reported in potato in southern New Jersey.
  • Bacterial leaf spot is being reported on pepper and tomato.
  • Basil downy mildew remains active. All basil growers should continue to scout and be proactive.
  • Late blight has been reported on potato as far north as North Carolina near the Virginia border. There have been no reports of late blight in the region to date. To track late blight in the US please visit http://usablight.org/
  • Cucurbit downy mildew has been reported on cucumber, butternut, acorn, and yellow summer squash as far north as central South Carolina and was reported on cucumber in Michigan this past week. To track the progress of CDM in the US please visit http://cdm.ipmpipe.org/. Fungicide maintenance programs should focus on cucurbit powdery mildew control until CDM is reported in the region.
Filed Under: Vegetable Crops
June 23, 2015

The Weather of Late:
A Double-edged Sword

The weather has been a double-edged sword of late throughout most of the mid-Atlantic region. The extremely hot weather with temperatures at or above 90 these past few days have been good for slowing disease development down. At those temperatures, its even too hot for pathogens to develop!

Unfortunately, the weather has also brought with it a lot of wind and rain these past few days and weeks. We all know what this leads to. Remember that bacteria need a wound or natural opening to enter a plant and cause an infection. The heavy winds and driving rains that beat up plants also help create the wounds that allow this to occur so its not unlikely to see an uptick in bacterial problems across a number of crops, such as in the case of bacterial leaf spot in tomato and pepper, after the weather we’ve had this past week.

Growers need to be proactive with copper applications and/or disinfestant applications prior to and/or after such events. Growers should also avoid working in fields when foliage is wet, if possible. This is extremely important if a bacterial problem is already present in the field!

The wet weather, along with the high humidity and prolonged leaf wetness also makes nice for many fungal pathogens, both leaf and soil-borne. Phytophthora blight in cucurbits, pepper, eggplant and tomato;  Early blight in tomato;  Alternaria and Anthracnose in cucurbits; and downy mildews just to name a few are favored by our current weather conditions, especially after temperatures cool down after todays weather front passes through the region.

During these conditions, all growers need to remain diligent and keep up with their protectant fungicide programs as long as field conditions allow and be proactive instead of reactive. After today, we get a few hours of dry weather before potential rains return on Thursday night into Friday.

Filed Under: Vegetable Crops
June 23, 2015

Vegetable Disease Briefs – 6/23/15

  • Basil downy mildew has been reported in Northern New Jersey this past week. All basil growers should continue to scout and be proactive.
  • Late blight has been reported on potato as far north as North Carolina near the Virginia border. There have been no reports of late blight in the region to date. To track late blight in the US please visit http://usablight.org/
  • Cucurbit downy mildew has been reported on cucumber, butternut, acorn, and yellow summer squash as far north as central South Carolina. To track the progress of CDM in the US please visit http://cdm.ipmpipe.org/
  • Bacterial leaf spot are coming in on pepper and tomato.
  • Black leg has been reported in potato in southern New Jersey.
  • Phytophthora blight on pepper and cucurbit crops has been reported. The heavy rains that have come into and remain in the region have been ideal for P. capsici. All growers need to scout on a regular basis and be proactive.
  • Early blight has been reported in tomato.
Filed Under: Vegetable Crops