Vegetable Crops Edition

Seasonal updates and alerts on insects, diseases, and weeds impacting vegetable crops. New Jersey Commercial Vegetable Production Recommendations updates between annual publication issues are included.
 
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April 8, 2020

Controlling purple blotch in leeks and onion

Purple blotch – Purple blotch, caused by Alternaria porri, may survive on infected plant material in overwintered plantings and may cause problems in spring transplanted fields and seedbeds.  Symptoms of Purple blotch include tannish-brown, elongated, concentric, circular lesions with chlorotic margins with lesions running parallel with leaf veins. As the weather begins to warm up and spring showers arrive Purple blotch may become problematic in some fields.  Spores are produced and new plants infected during periods of warm (77-85°F) humid weather. Symptoms appear 1 to 4 days after infection and black spores are produced in new lesions within 5 days. Spores are produced at night and released in the morning as humidity decreases. The spores are spread by wind and splashing rain or irrigation. Typical lesions occur when the leaf wetness duration is >16 hours. Control of Purple blotch begins with preventative fungicide applications.

Code Product Name Product Rate

 

 Active Ingredient(s)

(*=Restricted Use)

 PHI

(d)

 REI

(h)

 Bee

TR
Apply the following preventatively prior to the onset of disease. Do not apply chlorothalonil more than 3 times per season.
M05 chlorothalonil 6F 1.5 to 3.0 pt/A chlorothalonil 14 12 N
Tank mix or rotate the above with one of the following FRAC code 3, 7, or 11 fungicides when conditions favor disease development or when symptoms are present in the field. Rotate fungicides with different modes of action.
3 Folicur 480SC 4.0 to 6.0 fl oz/A tebuconazole 7 12 N
3 + 9 Inspire Super 2.82EW 16.0 to 20.0 fl oz/A difenoconazole + cyprodinil 7 12 —
3 + 11 Quadris Top 1.67SC 12.0 to 14.0 fl oz/A difenoconazole + azoxystrobin 7 12 —
7 Endura 70W 6.8 oz/A boscalid 7 12 —
7 Fontelis 1.67SC 16.0 to 24.0 fl oz/A penthiopyrad 0 12 L
7 + 11 Pristine 38WG 10.5 to 18.5 oz/A boscalid + pyraclostrobin 7 12 —
11 Cabrio 20EG 8.0 to 12.0 oz/A pyraclostrobin 7 12 N
11 azoxystrobin 2.08F 6.0 to 12.0 fl oz/A azoxystrobin 4 0 N

Applications of azoxystrobin, Cabrio, or Pristine at high rates will also help suppress Downy mildew.

Filed Under: Vegetable Crops
April 6, 2020

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.

Freeze injury in asparagus

Fig 1a. Freeze injury in asparagus. (Photo by Tom Orton)

Freeze injury in Asparagus

Fig 1b. Freeze injury in Asparagus. Note the color of the interior of the spear. (Photo by Tom Orton)

 Freeze Injury – About 10 days ago temperatures dipped well below freezing for a night or two, and combined with the higher than normal temperature this spring, some asparagus fields that had already started to produce spears were hit with injury. Affected spears will be bent/distorted and begin to breakdown and rot (Fig. 1a).

Cutting frozen spears will show the discoloration of the spear caused by the freeze (Fig. 1b).

Fig. 2. 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.2).

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Filed Under: Vegetable Crops Tagged With: , , ,
April 6, 2020

Controlling Septoria Leaf Spot and Bacterial Leaf Blight in Parsley

Septoria leaf spot (SLS) in Parsley can cause significant losses in fields where it has become established. Like other Septoria’s, the leaf spots produced on parsley look much like the leaf spots produced on tomatoes and other crops. Septoria leaf spot overwinters from year to year on infected debris so long crop rotations of 2 or more years are important to help reduce disease pressure. During the season, SLS will spread rapidly with each subsequent rainfall and/or overhead irrigation event. Therefore, early detection and preventative fungicide applications are key to successfully controlling SLS. There have been a few new fungicides labeled for SLS control in the past few years.

Parsley SLS

Septoria leaf spot of Parsley

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

Vegetable Disease Update – 4/4/20

Warmer days and cool nights, along with cool soils and the regular wet weather has made conditions ideal for disease development in some spring crops. Growers should consider applying preventative fungicide applications for early-season diseases, particularly root rots, either in the transplant water or shortly after transplanting or seeding to help mitigate potential issues. All fields should be scouted on a regular basis. White rust and anthracnose were reported on spinach this week, so leaf spot pathogens are already active.

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

Controlling white mold in spring crops

White mold, or lettuce drop, caused by Sclerotinia sclerotiorum, can cause serious losses in lettuce and other susceptible crops if left uncontrolled. Disease development is favored by wet, humid conditions (especially in high tunnels and fields) with known histories of the disease.

WhiteMold

White mold on lettuce. Notice the white fungal growth and black sclerotia developing on the base of the stem. The sclorotia can survive in the soil for up to 10 years.

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Filed Under: Vegetable Crops Tagged With:
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