Andy Wyenandt

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

Vegetable Disease Update – 4/17/17

Vegetable Disease Notes:

  • Powdery mildew has been reported in a number of tomato greenhouse operations. For control of powdery mildew and other important diseases in greenhouses and high tunnels please see Table E14 on pages E52-E54 of 2016-2017 Commercial Vegetable Production Recommendations Guide.
  • A new article on the importance of testing for Dickeya dianthicola in potato seed can be found here.

[Read more…]

Vegetable Disease Update – 4/10/17

Asparagus

Phytophthora crown and spear rot – In fields with low spots (poorly drained soils) or fields with a history of crown and/or spear rot apply Ridomil Gold 4SL (mefenoxam, 4) at 1.0 pt/A, or Ultra Flourish 2E/A (mefenoxam, 4) at 2.0 pt/A, or MetaStar 2E (metalaxyl, 4) at 2.0 qt/A over beds just before 1st harvest. For new plantings, apply the same after planting or after crown covering. Do not apply Ridomil or MetaStar one day prior to harvest or illegal residues may result. For more information please see the 2016-2017 Mid-Atlantic Commercial Vegetable Production Recommendations Guide. [Read more…]

Controlling Spring Diseases in Asparagus

Asparagus season is just around the corner and now is a good time to review important diseases.

Wet soil conditions are ideal for Phytophthora and Pythium development. To help reduce potential losses, especially in fields with low spots or fields that are poorly drained soils, or more importantly, in fields with a history of either disease apply Ridomil Gold 4SL (mefenoxam, 4) at 1.0 pt/A, or Ultra Flourish 2E/A (mefenoxam, 4) at 2.0 pt/A, or MetaStar 2E (metalaxyl, 4) at 2.0 qt/A over beds just before first harvest. For new plantings, apply the same after planting or after crown covering. Do not apply Ridomil or MetaStar one day prior to harvest or illegal residues may result. [Read more…]

Got humidity? Get rid of it!

Unfortunately, closed greenhouses retain heat and humidity which can spell problems if left unchecked.

Remember, high relative humidity equals wet leaves which favor the development of fungal diseases such as Botrytis or bacterial diseases such as bacterial leaf spot. To avoid potential problems, do your best to vent out as much humidity as possible in the late afternoon and/or early morning. Turn on circular fans to promote air movement and finish watering earlier enough in the day so leaves have enough time to dry out before nightfall.

As a side note, stressed transplants where water and/or fertility have been withheld are also more prone to disease development. A light fertilizer application may go a long way in improving transplant health before setting in the field.

Please see Table E-14 and pages E52-E54 of the 2016-2017 Commercial Vegetable Recommendations Guide for a list of control options for important diseases in greenhouses.

Best management practices for managing Dickeya dianthicola in potato – 2017

Using PCR test results and North American Certified Seed Potato Health Certificates to track Lot no., Dickeya dianthicola was reported in 22 states (ME, DE, FL, MD, MA, MN, NJ, NY, NC, PA, RI, VA, WV, WI, OH, IN, MO, MI, TX, ND, ID, and NM) on at least eleven potato varieties in 2016. Some of these varieties included: ‘Reba’, ‘Superior’, ‘Vivaldi’, ‘Norwis’, ‘Snowden’, ‘Yukon Gold’, ‘Beacon Chipper’, ‘Kennebec’, and ‘Atlantic’.  Known sources of infested seed found in potato fields on the East Coast have originated from WI, at least two suppliers in New Brunswick, Canada, and a number of seed suppliers in Maine this past growing season. To better understand the scope and breadth of the pathogen affecting potato production on the East Coast and elsewhere, information on known varieties and lot numbers that tested positive for Dickeya this past summer have been collected. Information on suspect varieties and lot numbers based on FL tests results from this past winter have also been collected. This information is now widely available. Of importance to all NJ potato growers, is that there have been NO CHANGES in the current policy or Blackleg tolerance levels for mitigating Dickeya dianthicola in seed production. All growers are encouraged to follow best management practices for buying seed and best management practices for Dickeya in field production. If you suspect Dickeya dianthicola in potato seed during cutting or planting please contact your county Extension agent or Extension Specialist. All suspect potato samples should be PCR tested to confirm the presence of Dickeya dianthicola.

 The best method for keeping your potato operation Dickeya-free is to adopt your own 0% Dickeya-tolerance policy.

Understanding Damping-off Pathogens in Transplant Production

Damping-off is caused by a number of important vegetable pathogens and is very common during transplant production and early-spring. Damping-off can kill seedlings before they break the soil line (pre-emergent damping-off) or kill seedlings soon after they emerge (post-emergent damping-off). Common pathogens that cause damping-off include Pythium, Phytophthora, Rhizoctonia and Fusarium spp.

It is extremely important to know which pathogen is causing the damping-off problem and which fungicide to properly apply.

[Read more…]