Andy Wyenandt

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

April 4, 2020

Damping-off: Identifying and Controlling Early-Season Damping-off Pathogens

It is extremely important to know which pathogen is causing damping-off problems and which fungicide to properly apply. The key to controlling damping-off is being proactive instead of reactive. Always refer to the fungicide label for crop use, pathogens controlled, and application rates.

Damping-off is caused by a number of important vegetable pathogens and is very common during the 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.

Control of damping-off depends on a number of factors. First, is recognizing the conditions which may be leading to the problem (i.e., weather/greenhouse growing conditions) and second, identifying the pathogen causing the problem.

Conditions Favoring Damping-off

Although all four pathogens are associated with damping-off, the conditions which favor their development are very different. In general, Phytophthora and Pythium are more likely to cause damping-off in cool, wet or overwatered soils that aren’t allowed to dry out due to cloudy weather or cooler temperatures. Conversely, Rhizoctonia and Fusarium are more likely to cause damping-off under warmer, drier conditions especially if plug trays are kept on the dry side to help reduce transplant growth. [Read more…]

Filed Under: Vegetable Crops
April 4, 2020

Organic Transplant Production: Suppressing Soil-borne Pathogens – A reminder

Pathogens such as Fusarium, Pythium, Phytophthora, Thielaviopsis and Rhizoctonia that cause pre- and post-emergent damping-off can cause serious problems in organic (and conventional) transplant production. The key to controlling and/or suppressing damping-off pathogens with biological controls is keeping the biological populations high and continually present on root surfaces of the host, and by following good cultural practices. [Read more…]

Filed Under: Vegetable Crops Tagged With: , ,
April 4, 2020

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 Orondis Gold (oxathiapiprolin + mefenoxam (FRAC groups 49 + 4) at 4.8 to 9.6 fl oz/A, 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 Orondis Gold, Ridomil, Ultra Flourish, or MetaStar one day prior to harvest or illegal residues may result. [Read more…]

Filed Under: Vegetable Crops Tagged With:
April 2, 2020

Vegetable Disease Update – 4/2/20

  • White rust and Anthracnose have been reported in spinach in southern New Jersey this week.
  • Symptoms of white rust include yellow lesions on the upper leaf surface and white blister-like pustules on the underside of the leaf. Generally, the upper surface of the leaves remain chlorotic, however in advanced stages, white lesions may form on the upper side of the leaf. White rust caused by Albugo occidentalis is an oomycete, or ‘water mold’, and its development is favored by cool, wet weather with extended periods of leaf wetness. Spinach leaf surfaces must remain wet for at least 2 to 3 hours or longer to allow infection to occur, with the optimum temperature for spore germination at 54°F. The disease develops most rapidly during periods of cool, humid nights and mild daytime temperatures.
  • Anthracnose in spinach is caused by Colletotrichum dematium. Symptoms of anthracnose are small, circular, water‑soaked lesions on young and older leaves. Lesions enlarge, turn brown to tan in color, and become thin and papery. In severe cases, lesions coalesce and result in severe blighting of foliage. Diagnostically, tiny black fruiting bodies (acervuli) which look like small black hairs form profusely in diseased tissue and are a characteristic feature of the disease. The presence of acervuli distinguishes anthracnose from Cladosporium and Stemphylium leaf spot diseases, which also form circular lesions on infected spinach.
  • Importantly, the fungicides to control White rust will be different for those used to control Anthracnose in spinach
  • Anthracnose crown rot, caused by Colletotrichum gloeosporioides, has been reported in strawberry this week. Symptoms of anthracnose crown rot include the “marbling” of the crown tissue.  Cutting the crown lengthwise reveals white and reddish brown streaks, creating a marbled effect, with a dry rot-like appearance. Initial symptoms include plant stunting and flagging of young leaves due to lack of water. Initially plants wilt in the heat of the day, which is often over-looked as drought or heat stress. In advanced infections, the entire plant will die.
  • For more information on White rust, Anthracnose in spinach, and Anthracnose crown rot control in strawberry please the 2020/2021 Mid-Atlantic Commercial Vegetable Production Recommendations guide.  The new guide is now available FREE on-line or can be purchased in hardcopy form through your county agricultural office in New Jersey. The complete 2020/2021 Vegetable Production Recommendations guide or specific sections can be downloaded depending on your production needs.
Filed Under: Vegetable Crops Tagged With: , ,
March 21, 2020

Vegetable Disease Update – 3/21/20

  • Late blight has been reported on tomato in central Florida. This is the first report of Late blight in the US this growing season. To follow Late blight outbreaks in the US please sign up for alerts at the USAblight website by clicking here.
  • There have been no reports of cucurbit downy mildew in the US to date. To track, monitor, and receive reports on CDM development in the US please click here. For the current understanding of what is happening with the CDM population in the US and current control recommendations please click here.
  • There have been no reports of basil downy mildew in the US to date. To track and receive reports on its whereabouts in the US on the new website please click here. For current BDM control options in the greenhouse and field please click on hyperlinks.
  • For the updated list of fungicides for use in the control of important diseases in the greenhouse please click here.
  • Commercial growers should consider adding at-transplanting or -seeding controls for Phytophthora and Pythium root rots as we head into the spring especially if soils remain wet. For more information please click here. Organic growers can find more information on controlling important root rot pathogens in early season transplant production here!
  • Transplant producers need to remember to vent their structures to reduce relative humidity buildup going into the evenings to help reduce leaf wetness during the overnight.
  • With strawberry season just around the corner, please click here for information on controlling important fruit rot pathogens.
  • The 2020/2021 Commercial Vegetable Production Recommendations Guide is available for free online! With many county offices running reduced hours or being closed this is the easiest way to obtain the newest recommendations.
  • For a quick review on managing fungicide resistance development using tank mixes and fungicide rotations, and in FRAC group 3 and FRAC group 11 fungicides please click on hyperlinks.
  • To keep up with Rutgers Extension services please click here. We are here to help!
Filed Under: Vegetable Crops
February 28, 2020

New cucurbit downy mildew forecasting website up and running for 2020

For cucurbit growers who have been using the CDMpipe website the past few years to track the progress of cucurbit downy mildew in the US, a new website has been relaunched for the 2020 growing season. Importantly, for those you have signed up in the past you should be receiving an email in the near future asking you to sign up for the new website. You can visit the new website by clicking here. Click on the Alerts tab at the top of the page and fill out the form to receive alerts!

Filed Under: Vegetable Crops Tagged With: ,