Posts Tagged ‘spinach’

Spinach Foliar Diseases

Thursday, May 24th, 2012

Kate Everts, Vegetable Pathologist, University of Delaware and University of Maryland; keverts@umd.edu

Downy mildew of spinach has been found in the mid-Atlantic. This disease is not common in Maryland or Delaware, but I do see it occasionally. Symptoms begin with light spots on the upper surface of the leaf, followed by purple to grey fungal growth on the lower leaf surface (Figure 1).


Figure 1. Downy mildew sporulation on spinach leaves.

White rust (Albugo occidentalis) occurs more frequently in Maryland and Delaware. White rust symptoms begin with light green areas on the upper surface of the leaves. However in the case of white rust, the sporulation on the underside of the leaves is white, not grey (Figure 2). A third common spinach disease is anthracnose (Figure 3). Anthracnose is characterized by small tan lesions on leaves. Scout your spinach plantings and determine whether a disease is present. See the Commercial Vegetable Recommendation Guide for several effective fungicide options. Read the labels carefully because some fungicides applied at high temperatures may be phytotoxic, and many available and effective products, if used improperly, will result in resistance development. Alternate fungicide classes within a spray program, and follow resistance management guidelines on the label.

 Figure 2. White rust infected leaves with chlorotic (yellow) lesions on the upper surface and sporulation on the under surface.

Figure 3. Anthracnose lesions are tan nectrotic (dead) spots on spinach leaves.

Lettuce and Spinach Disease Control

Thursday, April 26th, 2012

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Lettuce
We received a lettuce sample last week in the plant clinic from a high tunnel operation with lettuce drop. The following are the fungicide recommendations for the two lettuce diseases of importance in our area. These are best used preventatively. Spring lettuce season is beginning and growers should take precautions to help control Bottom rot (Rhizoctonia) and Lettuce drop (Sclerotinia) which may cause potential problems. For Bottom rot, apply Endura 70W (boscalid, FRAC code 7) at 8.0 to 11.0 oz 70W/A, or iprodione (FRAC code 2) at 1.5 to 2.0 lb 50WP/A or OLF should be applied one week after transplanting or thinning and 10 and 20 days later. For Lettuce drop, apply Endura (FRAC code 7) at 8.0 to 11.0 oz 70WG/A or iprodione (FRAC code 2) at 1.5 to 2.0 lb/A, or Quadris (azoxystrobin, 11) at 0.40 – 0.80 fl. oz/1000 row ft 2.08SC beginning one week after transplanting or thinning and again at 10 and 20 days later. For more information on control of Bottom rot and Lettuce drop and other important diseases of lettuce please see the 2012 Delaware Commercial Vegetable Production Recommendations Guide.

Spinach
If white rust or downy mildew are a concern on spinach, prior to symptom development, apply the following on a 7 to 10-day schedule: Quadris (azoxystrobin, 11) at 12.0 to 15.5 fl oz 2.08SC/A, or Cabrio (pyraclostrobin, 11) at 12.0 to 16.0 oz 20EG/A, or Reason (fenimadone, 11) at 5.5 to 8.2 fl oz 500SC/A, or Tanos (famoxodone +cymoxanil, 11 + 27 ) at 8.0 to 10.0 oz 50W/A. Rotate to one of the following fungicides: Ranman (cyazofamid, 21) at 2.75 fl oz 400F/A, Revus (mandipropamid, 40) at 8.0 fl oz 2.08F, or Presidio (fluopicolide, 43) at 3.0 to 4.0 fl oz 4SC/A, or Actigard (acibenzolar-S-methyl, P) at 0.50 to 0.75 oz 50WG/A, or Aliette (fosetyl Al, 33) at 3.0 lb 80WDG/A, or fixed copper (FRAC code M1) at labeled rates (Copper containing fungicides may cause some phytotoxicity), or Ridomil Gold Copper (mefenoxam + copper, 4 + M1) at 2.5 lb 65WP/A (on 14-day schedule). For more information please see the Delaware Commercial Vegetable Production Recommendations.


White rust on upper leaf surface

White rust on lower leaf surface of spinach

Dual Has a 24c Registration for Spinach in Delaware

Friday, August 19th, 2011

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Delaware has been granted a state registration (24c) for use of Dual Magnum in spinach. Growers in other states need to check with officials to ensure you have this registration. A few reminders: rate is 0.33 to 0.67 pt/A to the soil surface as a preemergence application i.e. prior to crop and weed emergence. Dual will not control emerged weeds. Irrigating spinach within two days of Dual application will ensure it gets moved into the soil. Restrictions: (1) Do not mechanically incorporate. (2) Do not apply this product through any type of irrigation system. (3) Only one application of Dual MAGNUM is permitted per spinach growing season. (4) Do not exceed more than 0.67 pt/A Dual MAGNUM. (5) Do not harvest with 50 days of application. Dual can cause injury to spinach and end user or grower accepts the risk of crop injury.

Bolting in Spring-Planted Vegetables

Friday, May 20th, 2011

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

Bolting is the term used for flower stalk formation in vegetables. Bolting response may be related to temperature, daylength, or a combination.

Bolting in spinach, lettuce, and some radishes (oriental types) will occur naturally as days get longer. High temperatures will accelerate bolting in spinach and lettuce.

Many mustard family plants need a cold period along with lengthening days to flower. The amount of cold needed depends on the species and variety. Mustards are very prone to cold initiated spring bolting; turnips, Chinese cabbage, and salad radishes require more cold to initiate the bolting response.

In the cole crop group, cabbage planted very early in cold springs may bolt and premature flowering in broccoli, cauliflower, kale, and collards also occurs when planted too early, or if the spring is abnormally cold. However, cole crop transplants have to be of a certain age to be susceptible to this cold-initiated bolting.

Other biennial vegetables such as beets, carrots, and onions also can be induced to bolt but only once plants have reached a certain size (they are past the juvenile growth stage). This is uncommon in our region.

Controlling bolting starts with planting during the recommended planting window. Early planting will contribute to bolting in some crops (such as cabbage), late planting in others (such as lettuce).

Select varieties that are adapted to the spring planting season (an example would be Savannah mustard). Chose slow bolting varieties of spinach and lettuce. Choose spring adapted varieties of oriental radishes and Chinese cabbage.

One issue that complicates this is the use of high tunnels for early production. High tunnels allow for earlier planting but cold snaps still may drop temperatures enough to cause the cold induced flowering response in many of these crops.

 

Change in Pre-Harvest Interval for Dual Herbicide on Spinach, Reminder on Waiver

Friday, September 17th, 2010

Gordon Johnson, Extension Vegetable & Fruit Specialist; gcjohn@udel.edu

The pre-harvest interval for Dual Magnum on spinach has been changed from 40 to 50 days. Growers are reminded that a Special Local-Needs Label 24(c) has been approved for the use of Dual Magnum 7.62E to control weeds in spinach in Delaware, Maryland, New Jersey, Pennsylvania, and Virginia. The use of this product is legal ONLY if a waiver of liability provided by the local growers association has been signed by the grower, all fees have been paid, and a label has been provided by the association.

In Delaware, the Fruit and Vegetable Growers Association of Delaware is the entity that holds these labels and waiver forms. Contact Gordon Johnson, Extension Vegetable and Fruit Specialist, University of Delaware, for waiver forms and copies of the revised label:

Gordon Johnson
Carvel Research and Education Center
16483 County Seat Highway
Georgetown, DE 19947
General Phone: (302) 856-7303
Direct Phone: (302) 856-2585 ext. 590
Cell Phone: (302) 545-2397
Fax: (302) 856-1845
Email: gcjohn@udel.edu

Soil Temperature and Vegetable Seed Emergence

Friday, April 24th, 2009

Gordon Johnson, Extension Ag Agent, Kent Co.; gcjohn@udel.edu

We have had a late spring with limited periods where soils were dry enough to plant spring crops. Warmer weather is being forecast for the coming week. However, soil temperatures currently are on the cold side. Cold, wet soils will lead to delays in crop emergence and potential loss of stand due to seed rots, seedling diseases, and insect feeding as fungicide and insecticide seed protectants dissipate. The longer the emergence period, the more risk to the crop.

The following are some guidelines for days to emergence at various soil temperatures for field seeded vegetable crops:

Beans (snap): at 50°F limited germination, at 59°F emergence takes 16 days, at 68°F emergence takes 11 days, at 77°F emergence takes 8 days, at 86°F emergence takes 6 days.

Beans (lima): at 50°F limited or no germination, at 59°F emergence takes 31 days, at 68°F emergence takes 18 days, at 77°F emergence takes 7 days, at 86°F emergence takes 7 days.

Cantaloupe: at 50°F limited or no germination, at 59°F emergence takes 14 days, at 68°F emergence takes 8 days, at 77°F emergence takes 4 days, at 86°F emergence takes 3 days.

Carrot: at 41°F emergence takes 51 days, at 50°F emergence takes 17 days, at 59°F emergence takes 10 days, at 68°F emergence takes 7 days, at 77°F emergence takes 6 days.

Cucumbers: at 50°F limited or no germination, at 59°F emergence takes 13 days, at 68°F emergence takes 6 days, at 77°F emergence takes 4 days, at 86°F emergence takes 3 days.

Lettuce: at 41°F emergence takes 15 days, at 50°F emergence takes 7 days, at 59°F emergence takes 4 days, at 68°F emergence takes 3 days, at 77°F emergence takes 2 days.

Okra: at 50°F no germination, at 59°F emergence takes 27 days, at 68°F emergence takes 17 days, at 77°F emergence takes 13 days, at 86°F emergence takes 7 days.

Onion: at 41°F emergence takes 31 days, at 50°F emergence takes 13 days, at 59°F emergence takes 7 days, at 68°F emergence takes 5 days, at 77°F emergence takes 4 days.

Peas: at 40°F emergence takes as much as 30 days, at 50°F emergence takes 10-14 days, at 59°F emergence takes 9 days, at 68°F emergence takes 8 days, at 77°F emergence takes 6 days.

Spinach: at 41°F emergence takes 23 days, at 50°F emergence takes 12 days, at 59°F emergence takes 7 days, at 68°F emergence takes 6 days, at 77°F emergence takes 5 days.

Sweet Corn: at 50°F emergence takes 22 days, at 59°F emergence takes 12 days, at 68°F emergence takes 7 days, at 77°F emergence takes 4 days, and at 86°F emergence takes 4 days. Sweet corn emergence success in cold soils will vary greatly depending on variety class. Shrunken seed types have low cold tolerance.

Watermelon: at 50°F no germination, at 59°F emergence takes 21 days, at 68°F emergence takes 12 days, at 77°F emergence takes 5 days, at 86°F emergence takes 4 days.

Of course, there are many factors that will modify days to emergence including soil moisture, seed vigor, seed quality, and variety.

Scout for Spinach Downy Mildew and White Rust

Friday, April 17th, 2009

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Scout spinach for downy mildew and white rust on a regular basis, especially if spring plantings are near overwintered fields. Beginning 2 to 3 weeks after emergence (and prior to symptom development), apply the following on a 7 to 10-day schedule: Quadris (azoxystrobin, 11) at 6.0 to 15.5 fl oz 2.08F/A (use high rate for downy mildew), or Cabrio (pyraclostrobin, 11) at 12.0 to 16.0 oz 20EG/A (use lower rate for white rust only). Rotate to one of the following fungicides: Actigard (acibenzolar-S-methyl, P) at 0.75 oz 50WG/A, or Aliette (fosetyl Al, 33) at 3.0 lb 80WDG/A, or fixed copper (FRAC code M1) at labeled rates (copper containing fungicides may cause some phytotoxicity), or Ridomil Gold Copper (mefenoxam + copper, 4 + M1) at 2.5 lb 65WP/A (on a 14-day schedule). For more information please see the Delaware Commercial Vegetable Production Recommendations Guide.