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…]
June 10, 2021 Andy Wyenandt
Organic Production: Suppressing Soil-borne Pathogens
June 9, 2021 Andy Wyenandt
Destroying cucurbit plantings after harvesting is a must to help mitigate downy mildew
It’s a little early in the season but now is a good time to start thinking about ways to help mitigate cucurbit downy mildew pressure later on. All cucurbit fields, especially cucumber and other summer squash fields should be destroyed immediately after the last harvest to help limit potential inoculum sources for cucurbit downy mildew, especially in later plantings.
For a review of CDM control please click here.
To track the progress of CDM on your phone or PC please visit the CDM forecasting website.
June 8, 2021 Andy Wyenandt
Basil downy mildew found in southern New Jersey – ALERT 6/8/21
Basil downy mildew has been confirmed in potted sweet basil being sold by a box-store in Cumberland County in southern New Jersey. This is the second report of BDM in the state and region this growing season. All basil growers are encouraged to scout their fields or greenhouses on a daily basis and should consider initiating a preventative fungicide program. [Read more…]
June 8, 2021 Andy Wyenandt
Recognizing Angular Leaf Spot in Cucurbits
Angular leaf spot is common in New Jersey and the region. It often shows up during cooler, wet weather and isolated rain.
Symptoms of angular leaf spot in cucurbit.
Angular leaf spot of pumpkin. Note leaf ‘shot holes’.
Angular leaf spot will first appear as, small water-soaked lesions which will expand until they reach a larger leaf vein resulting in the angular looking symptoms on leaves. Under heavy disease pressure, the bacteria will infect fruit causing small, water-soaked circular spots. In many cases once weather conditions become dry again, infected tissue in leaves will die and fall out leaving the characteristic ‘shot hole’ symptoms. Control of angular leaf spot begins with the application of labeled rates of fixed copper plus mancozeb to help suppress the spread of the disease until hot, dry weather returns.
June 7, 2021 Andy Wyenandt
Avoiding Plectosporium blight in cucurbit fields.
Plectosporium blight, also known as Microdochium blight or White speck, caused significant problems in some pumpkin fields last summer in New Jersey. The soil-borne fungal pathogen, although somewhat uncommon, can unexpectedly show up in some years and cause significant losses if left uncontrolled. The fungus survives in the soil on decaying plant debris where it can remain saphrophytic by surviving off organic matter. Infection is characterized by the production of numerous light tan to “bleached” spindle shaped lesions that develop on vines and the undersides of infected leaves. Heavily infected vines and leaves can die leading to premature defoliation and subsequent sunscald on fruit. In cases of heavy disease pressure, spores that are produced on the bottom sides of leaves fall and infect the topsides of fruit laying beneath the canopy. Infection of stems leads to premature browning and drying reduce their longevity. Fruit infection, in most cases, remain mostly cosmetic in nature reducing fruit quality and may predispose fruit to other opportunistic fruit rots. Plectosporium blight often shows up during periods of prolonged wet weather where the soil remains wet for extended periods. “Hot spots” typically appear in fields before the pathogen is further spread by driving rains and wind.
From a production standpoint, stay away from fields with known history of the disease for as long as possible; provide adequate spacing between plants in- and between rows (i.e., avoid the overcrowding of plants); avoid over (preplant) fertilization that can lead to thick, dense canopies; avoid overhead irrigation (if possible); avoid planting in area of a field that remains heavily shaded where soils tend to dry too slow.
Controlling Plectosporium blight begins with regular scouting, recognizing symptoms, and identifying “hot spots” in the field. Protectant fungicides, such as chlorothalonil, as well as those used in weekly maintenance spray programs for cucurbit powdery mildew control will help control Plectosporium blight as long they applied on a weekly schedule with a high volume of water with thorough coverage. To help improve control on the undersides of leaves, a FRAC code 11 fungicide such as Quadris Top or Pristine, can be added to the tank mix. Remember, FRAC code 11 fungicides have translaminar activity and will move from the top surface of the leaf to the bottom. Growers who grow powdery mildew resistant varieties need to remember to scout their fields regularly even if cucurbit powdery mildew has not been detected on the farm or if regular maintenance sprays haven’t begun.
White speck lesions covering the surface of immature and mature pumpkin fruit. White speck will only cause cosmetic injury to fruit.
White speck on vine and stem of infected pumpkin plant. Note the numerous small, white diamond shaped lesions.
June 6, 2021 Andy Wyenandt
Hot, Dry Weather and Transplant Death
Transplants that are not allowed to harden-off for a few days outside prior to setting in the field may suffer significantly. It is important to expose all transplants to some normal weather conditions before transplanting so they can become acclimated to light intensity as well as the wind and other field conditions. [Read more…]
