Veg Weekly Update and Blog 7/31/2024

Alliums: Market garden onions continue to go down and are being brought in for drying. Keep an eye out for bacterial soft rot symptoms at harvest and discard onions with a soft outer layer.

Brassicas: Heat stress symptoms are common in heading brassicas this time of year. Recently, we’ve fielded calls about “riciness” and off colors in crowns and leaf scorch in cauliflower leaves. More information on heat and uneven moisture impacts on cole crops can be found in this article by Dr. Emmalea Ernest of the University of Delaware.

Chenopods (Beets, Chard, Spinach): leaf miner pressure remains high in many areas. Translaminar insecticides can be used to kill miners in the leaves, which may also help reduce pressure from future generations.

Cucurbits:  Cucurbit Downy Mildew was found in cucumbers late last week in Washington County.  At this point growers in the entire region need to be including targeted fungicides along with their protective sprays.  For a list of those materials, click here.  Some of the earliest pumpkins are also starting to color up so maintaining good fungicides on these plantings is going to be important to reduce the loss of vine cover which increases the risk of sun scalding on the fruit.  Here is the link to the Powdery Mildew materials being recommended this year include Vivando (labeled for 3 applications max) alternated with a DMI fungicide (Proline, Procure, etc.).  Click here for the link to the Powdery Mildew fungicide table.

Nightshades: Bacterial canker has been identified in field tomatoes. To date, the outbreak has been limited to one variety.  Early identification, regular copper sprays and generally dry conditions have limited spread and fruit spotting. For more information on managing bacterial canker and other bacterial diseases of tomato, click here.

Potatoes:  Aphid populations have risen dramatically in the last week in many potato plantings.  The actual damage the aphids do to the plants is not the issue – the issue is aphids transmit many viruses such as PVY (Potato Virus Y).  Depending on the stage of the potato development, the thresholds vary slightly.  Since most potatoes are past tuber initiation, the threshold for aphids is 200 aphids/50 leaves.  If you have potatoes you are harvesting with green vines, that number jumps to 500 aphids/50 leaves.  Assail and Beleaf are good insecticide choices.

For those of you harvesting early or “new” potatoes, remember these harvesting tips to ensure the best quality:  First of all, if you can vine kill any of the foliage prior to digging (2 weeks or so), this will help to set the skins a bit so that they are not sloughing off as you dig or handle them.  In some cases, this can be hard to do because these vines are so vigorous they don’t want to die.  Vine killing can be accomplished many different ways – chemical dessicants, flaming, beating or even mowing.  Here is a link to a table of desiccants labeled in NY:  https://rvpadmin.cce.cornell.edu/uploads/doc_695.pdf

However, keep in mind that if there is any green tissue left, usually in the stems, you still should try to maintain a protectant fungicide program to limit disease infection to arial parts that can move into the tubers themselves.

Once you’ve dug your potatoes, you need to handle them very carefully, especially if they were not vine killed or were vine killed by not fully dried down yet.  If using a digger, removing the shakers can help a bit to reduce the skin abrasions.  If you can’t do that, run the chain slowly and keep as much dirt as far back on the chain as you can.  Even as you are picking them up, try not to handle them or dump them as few times as possible before getting them to market.

Lastly, do not put them directly through a washer right out of the field without allowing them to cool down a bit.  Also, remember to make sure the wash water is similar in temperature to the tubers – for most produce we aim for wash water that is within 10 degrees of the produce going into that water.  If the water is colder than the temperature of the potatoes water tends to get “sucked” back into the tuber resulting in bacterial soft rot issues.  And after washing let them dry completely before putting them in bags.  Do not put harvested potatoes directly into a cold storage.  Potatoes should go in a dark area and allowed to cool down gradually and heal or cure up a bit.  The best temperatures for this to happen is 60-65 degrees F for about 5 –20 days at a high humidity with good air circulation.  Cooling them down rapidly could result in condensation developing and encourage bacterial breakdowns.

Corn: Numbers of western bean cutworm continue to increase in the north, with over 100 moths captured at one site in Clinton County this week. Be aware, however, that large numbers of moths in traps do not always translate to major infestation in the field. For fresh market sweet corn, use a threshold of 1 egg mass per 100 plants when scouting. Look for egg masses on the upper sides of leaves at the top of the plant. Egg masses turn from pale gray to dark purple as they mature, and insecticides are most effective when applied near egg hatch. Many insecticides labeled for other caterpillar corn pests are also labeled for western bean cutworm.

True armyworm has also been detected in small numbers in sweet corn fields in the North Country and in the Capital District. So far, numbers have been small.

This week we continue to see populations of Corn Earworms remaining fairly consistent and still recommending a 4-5 day spray schedule of corn in green silk.  Rotating between Coragen or Besiege, Lannate and Radiant are still the best options for CEW control.  And even though we aren’t seeing Fall Armyworm moths in the traps, their damage is evident in many fields across the region.  Thresholds for FAW damage in fresh market sweet corn are 15% infestation at early tassel through tassel and 5% silk stage through harvest.  For early tasseling corn, this is probably the best time to control armyworm as they like to burrow into the tassel area and as the tassels open up, the worms are more exposed to the insecticides.  If corn tasseling is uneven, multiple applications might be necessary. Remember, FAW are resistant to synthetic pyrethroids (Warrior, etc.) so Lannate, Coragen and Radiant are still effective in controlling FAW.

 Miscellaneous: 

Celery anthracnose was found recently in many celery plantings, and is causing quick die-down of the crops. Symptoms of this disease include leaf curling, dead heart tissue, and brown stalk lesions. To prevent spread of anthracnose in a planting, rogue out infected plants and treat the crop with a fungicide. Avoid overhead irrigation and splashing of soil onto plants. Scout regularly, as this disease can progress more quickly under hot and humid conditions. For more information and labeled fungicide recommendations, see Elizabeth Buck and Meg McGrath’s fact sheet on this disease.

 

 

Managing Tomato Bacterial Diseases? Biopesticides Could Help.
Amara Dunn, NYS Integrated Pest Management Program
Chris Smart, Plant Pathology and Plant-Microbe Biology, Cornell University

Are you using copper to protect your tomatoes from bacterial diseases? Research from Cornell suggests that you could replace some of those copper applications with a biopesticide.

Preventing bacterial diseases on your tomatoes starts with good integrated pest management practices.

• > 3-year rotation out of tomatoes and peppers
• Clean seed or disease-free transplants
• Heat treat seed (unless it is pelleted or treated)
• Good sanitation in transplant production facility (e.g., new flats or sanitize between uses, sanitize greenhouse after each season)
• Inspect transplants and destroy any with symptoms of bacterial disease
• Do not work in tomatoes (e.g., tie, prune) when leaves are wet
• Either sanitize tomato stakes between growing seasons, or use new stakes each year (preferred)
• If you have an outbreak, till in plant debris quickly.

 

If you are doing all of these things and still need some extra protection from bacterial diseases (e.g., in a wet growing season), pesticides might also be in your IPM toolbox.

In New York, we’re fortunate that so far few bacterial isolates have been found to be resistant to copper. Copper resistance is a major problem in the southern U.S. and we’d certainly like to preserve its efficacy here in NY. Some people are also understandably concerned about the environmental impacts of using a lot of copper on their farms.

Cornell vegetable research programs led by Chris Smart and Meg McGrath have been testing products against our three bacterial diseases – spot (Xanthomonas), speck (Pseudomonas) and canker

(Clavibacter) for a number of years. So far, two products – Double Nickel LC (1 qt/A recommended) and LifeGard (4.5 oz/100 gal water) – have been rising to the top. When comparing these products alone to alternating either with copper, both worked better as replacements for some copper sprays than alone. Some research trials only included the biopesticide by itself, but the Double Nickel label states that it should be applied only tank mixed or rotated with copper-based fungicides.

Double Nickel alone (one year of data in Geneva) was as good as copper against bacterial spot. Double Nickel alone (two years of data in Geneva) and LifeGard alternated with copper (one year on Long Island) were as good as copper against bacterial speck. While neither product is registered (legal) for use against tomato canker, in research trials in Geneva, Double Nickel (one year) and LifeGard (two years) alternated with copper controlled canker as well as copper alone. So if you are replacing some copper sprays with

either Double Nickel or LifeGard, you’ll likely notice some incidental bacterial canker protection, too.

New to using biopesticides? The New York State IPM Program has a new resource to help. Biopesticide profiles (scroll to bottom of page) for Double Nickel, LifeGard, and seven other products provide

information on tank mix compatibility, shelf life, and other practical tips.

Changes in pesticide registrations occur constantly and human errors are possible. Read the label before

applying any pesticide. The label is the law. No endorsement of companies is made or implied.