Archives for April 2015

April 22, 2015

Growers Guide to Protectant Fungicides
(FRAC groups M1 – M11)

Protectant (contact) fungicides, such as the inorganics (copper, FRAC group M1) and sulfur (FRAC code M2); the dithiocarbamates (mancozeb, M3), phthalimides (Captan, M4), and chloronitriles (chlorothalonil, M5) are fungicides which have a low chance for fungicide resistance to develop. Protectant fungicides typically offer broad spectrum control for many different pathogens.

Why wouldn’t fungi develop resistance to protectant fungicides? Protectant fungicides are used all the time, often in a weekly manner throughout much of the growing season.

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Filed Under: Vegetable Crops Tagged With:
April 22, 2015

Spear Damage in Asparagus

Spear damage in asparagus can be caused by diseases such as Phytophthora spear and crown rot and purple spot. However, other environmental factors during the spring can damage spears as they emerge from the soil.

Fig. 1. Wind damage of asparagus spears. Notice how all spears are pointed in the same direction

 Wind – Periods of heavy winds during emergence will cause spears to bend.Winds can cause one side of the spear to dry out quicker than the other causing the spear to bend and point in the direction of the prevailing wind. An asparagus planting is suffering from wind damage if most of the bent spear heads in the bed are pointing in the same direction (Fig.1).

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Filed Under: Vegetable Crops Tagged With:
April 22, 2015

Vegetable Disease Briefs – 4/22/15

  • Quadris 2F from Syngenta, the first strobilurin (FRAC group 11) fungicide on the market, is coming off patent and a number of companies are expected to apply to manufacture and sell is under another name. Thus, in the 2015 Vegetable Recommendations Guide you will see references to Quadris (FRAC group 11) switched to azoxystrobin (FRAC group 11) much like we did with changing Bravo WeatherStik (M5) to chlorothalonil a few years ago. As more FRAC group 11 fungicides come off patent in the next few years we expect to do the same.
  • Cucurbit downy mildew is presently active on acorn, butternut, yellow summer, cucumber, cantaloupe, and giant pumpkin in southern Florida. To track the progress of cucurbit downy mildew in the US please visit (http://cdm.ipmpipe.org/)
  • Basil downy mildew is active in southern Florida.
Filed Under: Vegetable Crops
April 21, 2015

Vegetable Disease Update 4‑20‑15

This week in the Vegetable Disease Update:

  • Asparagus
  • Cabbage
  • Cole crops
  • Leeks
  • Lettuce

Note: The new 2015 NJ Commercial Vegetable Production Recommendations is available online.

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 2015 New Jersey Commercial Vegetable Production Recommendations Guide.
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Filed Under: Vegetable Crops
April 21, 2015

Controlling purple spot in Asparagus

Purple spot, caused the soil-borne fungus, Stemphylium vesicarium, can cause problems in cool, wet springs as well. Symptoms, just like its name, include numerous, sunken oval-shaped spots on spears during the harvest season and more importantly on ferns and stalks during the summer months as long as conditions are ideal for its development.

Twelve hours of wetness is needed for infection and the disease is exacerbated by wind-blown sand injury. Heavy purple spot infection during the summer will lead to premature defoliation which will decrease carbohydrate reserves for the next production season. With the season we had last year and the wet spring we’ve had thus far this year season, pressure due to purple spot may be high. Control of purple spot can be difficult because of management issues (i.e., the mowing and chopping up and leaving of old fern material in the field) and because fungicides can’t be applied during the harvest season. Growers who had pre-mature defoliation issues last year may expect problems this spring. Controlling purple spot begins with preventative fungicide applications during summer and fall by reducing infections to ferns and stalks. Weekly scouting and timely fungicide applications once fern stalks are full size should be done. Apply and rotate azoxystrobin at 6.2 to 15.5 fl oz 2.08F/A or chlorothalonil at 2.0 to 4.0 pt/A.

Filed Under: Vegetable Crops
April 21, 2015

Suppressing Soil-borne Pathogens in Organic Transplant Production

Pathogens such as Fusarium, Pythium, Phytophthora, Thielaviopsis and Rhizoctonia that cause pre- and post-emergent damping-off can cause serious problems in organic transplant production.

Remember, Phytophthora and Pythium are more likely to cause damping-off in cool, wet soils. Conversely, Rhizoctonia and Fusarium are more likely to cause damping-off under warmer, drier conditions. In general, Pythium tends to kill seedlings before they emerge whereas Rhizoctonia and Fusarium tend to kill seedlings after emergence. There are exceptions to the rules, but none the less, all damping-off pathogens can cause serious losses if not identified and controlled properly. Remember seeds or transplants that sit in cold, wet soils for prolonged periods of time are more prone to damping-off. Outside weather conditions also play an important role in potential disease development in spring transplant production. Most importantly, daily watering schedules need to be monitored and/or adjusted so as not to overwater during cool, cloudy periods or underwater during bright, warm, sunny days. Always do your watering early enough in the day so leaves are dry going into the overnight. [Read more…]

Filed Under: Organic Production, Vegetable Crops Tagged With: ,