Rutgers Cooperative Extension
An unexpected sample walked into the laboratory at the end of last week. Net blotch, which is caused by the fungus Drechslera dictyoides, was subsequently diagnosed on a sample of turf-type tall fescue.
Net blotch leaf lesions on tall fescue. Photo: Sabrina Tirpak, Rutgers PDL
The DMI (DeMethylation Inhibitors) or SBI (Sterol Biosynthesis Inhibiting) fungicides belong to FRAC code 3 which include the triazoles and imidazoles. Some of these fungicides are commonly known as Tilt (propiconazole), Rally (myclobutanil), Folicur (tebuconazole), and Procure (triflumizole). [Read more…]
Downy mildew was identified in Knock Out® rose samples submitted to the Plant Diagnostic Lab from a south-Jersey nursery this week. Knock Outs®, which have few problems, have been a favorite in New Jersey landscapes in recent years. Unfortunately, it seems this plant has met its Achilles’ heel.
Downy mildew on Double Knock Out® rose. Photo: Sabrina Tirpak, Rutgers PDL
Leaf spots were reported in spinach and other greens this past week. Growers should remain diligent and scout on a regular basis. With the dry weather expected over the next week, any use of overhead irrigation will help spread potential disease. Growers should apply preventative fungicides in advance of any disease developement or use of overhead irrigation.
Rhizoctonia was found in strawberry this past week. Rhizoctonia tends to show up during dryer weather periods usually on stressed plants. In general, the longer transplants sit in the ground without getting established and putting on any new growth the more susceptible they become to pathogens such as Rhizoctonia. Abound (azoxystrobin, 11) at 6.0 to 15.5 fl oz as a foliar application, or 0.40 to 0.80 fl oz/1000 ft row has a broad label for Rhizoctonia suppression across many crops. Abound will also help control pathogens such as anthracnose fruit rot, leaf spots, and powdery mildew in strawberry.
 Note brown hyphae growing on surface of infected root |
Rhizoctonia root rot on infected strawberry. |
 Note circular spots with dark red margins |
Leaf spot on strawberry. |
 Note: Secondary pathogens such as Alternaria can infest bleached out areas of stems over time |
Sunscald injury on stems of newly transplanted pepper seedlings caused by stems laying against edges of black plastic mulch on hot, sunny days. |
Downy Mildew and Alternaria – Symptoms of downy mildew include purple to yellowish-brown spots on upper leaf surfaces. A grayish-white spore mass will develop and cover the underside of leaves under ideal temperatures (night temperatures of 46 to 61°F and day temperatures below 75°F. Downy mildew can kill young plants. Heavily infected leaves may drop providing entry points for bacterial infections (black rot and soft rot).
Symptoms of Alternaria on infected leaves include small, expanding circular lesions with concentric rings that may have a ‘shot-hole’ appearance as lesions age. Heavily infected seedlings may result in damping-off. [Read more…]
