Vegetable Crops Edition

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January 12, 2020

Rutgers downy mildew resistant sweet basils available around the world; Research efforts continue

Rutgers downy mildew resistant sweet basils available around the world; Research efforts continue

After a decade’s worth of research and breeding efforts Rutgers Downy Mildew Resistant (DMR) sweet basils are now available to commercial and organic growers as well as home gardeners around the world. Since 2007, when basil downy mildew (BDM) was first identified in FL, the disease has caused significant economic losses to commercial basil growers everywhere, and made growing sweet basil in the backyard garden nearly impossible. Basil downy mildew has commonly led to total crop loss for organic growers under field cultivation systems. The presence of any BMD on fresh leaves will make the product unmarketable. Of further concern is that the pathogen favors high relative humidity. Certain temperature range which can make a basil crop appear to be free of downy mildew (e.g., at times over the season or after a harvest when weather is too hot and dry), then full of disease upon arrival to the distributor or retailer because of the environmental conditions of the packaged basil during distribution and shipping which often favors its growth. Since 2009, Rutgers has been working diligently to identify and breed downy mildew resistance into commercially acceptable sweet basils that have the correct aromas, essential oils, and flavors. The first of these four new DMR sweet basils are available through  your favorite seed company in North America, the European Union, and Australia.

Each of the new Rutgers DMR sweet basils have their own unique characteristics which can be matched to meet grower needs.

Rutgers Obsession DMR: An excellent sweet basil for field or potted plant production; will also make an excellent edible landscape plant; more compact, slower initial growth than Devotion DMR and Thunderstruck DMR, but for overall season is high yielding, lends itself to multiple cuts, and has a high leaf-to-stem ratio – good for small bunches or small size clam shells – dark green, thick, glossy leaves, flowers form very late; and highly resistant to Fusarium wilt.

Rutgers Devotion DMR: An excellent Genovese-type sweet basil for field production for fresh markets; establishes in the field or pots quicker than Rutgers Obsession DMR, with uniform, upright growth, dark, green color with flat to cup-shaped leaves. The Rutgers Devotion DMR is a beautiful plant.

Rutgers Thunderstruck DMR: An excellent sweet basil with high yields needed for processing- and fresh-market production; quick establishment and fast, upright growth with medium-sized, ruffled leaves with a bright green color.

Rutgers Passion DMR: An excellent sweet basil for potted plant and field production. Exhibits vigorous growth with high leaf-to-stem ratio; larger, slightly cupped leaf and similar aesthetics to Rutgers Devotion DMR.

Over the past 10 years, great research efforts have been made around the world to better understand and control basil downy mildew.

Understanding basil downy mildew

Basil downy mildew (BDM) is an obligate parasite, just like with all downy mildews, the pathogen needs a living host to survive. In northern regions, this means the pathogen will die out when basil crops freeze with the first frost in the fall. In areas of the south, such as southern Florida, the pathogen could survive year round as long as living basil is present. In greenhouse production (even in northern regions that freeze), as long as basil is in production the pathogen could be present. Research from Israel and Italy suggest that the pathogen can undergo sexual reproduction leading to the production of oospores, much like Phytophthora capsici, the causal agent of Phytophthora blight in pepper. This has profound effects on the pathogen – the opportunity to overwinter, develop new races, and its ability to develop fungicide resistance. For growers, this means that all downy mildew resistant basils still need to be grown with excellent management and with a proper spray program to ensure excellent control season-long.

Oospore production and overwintering

Oospore production via sexual reproduction in BDM has been confirmed in Europe, but not officially in the US to date. Oospore production suggests that mating types of the pathogen may be present. One early study from Israel showed that oospores were incapable of infecting plants. Importantly, oospore production in BDM could allow it to overwinter in soils drastically changing the way growers will have to manage the disease. Instead of waiting for BDM sporangia to arrive on your farm via weather patterns from other location or from infested seedlings, transplants, or plugs coming from more southern regions, the pathogen would already be present in your soil, and as long as weather conditions were favorable, the pathogen could cause disease. Thus, in more Northern regions, BDM could show up much sooner in the growing season. More work on understanding the role of oospore production in the lifecycle of BDM needs to be done. Growers must remain diligent and closely monitor their basil crop.

Basil downy mildew race development

Downy mildew pathogens in other cropping systems are known to develop new races over time. In spinach, for example, there are over 20 races of the pathogen. Importantly, the development of new races of the BDM pathogen would allow it to overcome current genetic resistance, meaning new genes for resistance would need to be bred into the host. In theory, for every new race of BDM that might develop, a new resistance gene or set of resistance genes would need to be bred into the host. Research in understanding the sweet basil genome as well as the pathogen’s genome is still in its relative infancy, but work at Rutgers and other Universities is currently ongoing. Understanding the genetic diversity of BDM in the US is a top priority of researchers with Rutgers collaborating with colleagues at UMASS, Cornell, and the University of Florida. Importantly, finding new sources of natural genetic resistance is also a top priority for all those involved in breeding for resistance to BDM. Research in each of these important areas to ensure continued genetic and plant breeding for basil downy mildew resistance is ongoing due to funds from the United States Department of Agriculture to the US universities listed.

Fungicide resistance development in BDM

Downy mildews in other crop systems are known to develop fungicide resistance. In recent years, mefenoxam insensitivity has been found in basil in Europe, but not the US to date. This suggests, along with knowledge of other downy mildew pathogens that fungicide resistance is most likely to develop in BDM. In recent years, a number of new fungicides with different modes-of-action have been registered for use in controlling BDM. Some of these fungicides have a high-risk for resistance development because of their active ingredient(s) and specific modes-of-action. Commercial basil producers need to take all the precautions to help mitigate fungicide resistance development. This means carefully following the use restrictions on the label and rotating among fungicides with different modes-of-action (e.g., rotating between fungicides in different FRAC codes).

Is basil downy mildew seed-borne?

Research has shown that BDM can be detected on the surface of seed using real-time PCR methods, but this method does not detect whether the pathogen is viable or not. Grow-outs of infested basil seed have been somewhat mixed; with some research showing it may be possible and others showing it is not possible. More work needs to be done and as such in the interim, it is better to assume it could be seed-borne.. For commercial growers and home gardeners, seed should always be purchased from reputable seed companies and growers should not harvest and save their own seed for possible re-infestation as studies have shown that BMD is detected on the seed collected from DMR and susceptible basil varieties. Some companies now offer propriety seed treatment methods for basil seed. When purchasing seed, you should ask if the seed has been treated and/or certified free of BDM.

Using BDM resistant sweet basils

In the past few years, along with the release of the new Rutgers DMR sweet basils, other sweet basils with BDM resistance have been commercially released in the US and Europe. It’s important for basil growers and homeowners to understand that none of the new DMR sweet basils are completely “immune” from getting BDM. The new DMR sweet basils are highly resistant to the pathogen compared to commercially-available susceptible varieties. Thus, in DMR resistant sweet basils the development of disease will be delayed – hopefully to much later in the growing season depending on your location, or not at all. Commercial and organic growers are encouraged to use DMR sweet basils along with best management practices, including appropriate fungicide use and good cultural practices, to help mitigate disease development.

For more information on basil downy mildew, our research, and our new Rutgers DMR sweet basils follow us on Instagram at RutgersBasil.

 

Filed Under: Vegetable Crops Tagged With: ,
January 10, 2020

Controlling Cercospora leaf spot in beet

Cercospora leaf spot (CLS), caused by Cercospora beticola, is an important and emerging disease in beet and swiss chard production in New Jersey. Efforts to control this disease has become more difficult in the past few years in some areas of southern New Jersey. The soil-borne fungal pathogen, once established in fields, can survive in the soil for up to 2 years on infected debris and on weed hosts such as Chenopodium, goosefoot, and pigweed. The pathogen may also be seed-borne. Symptoms of infection include numerous, small tan leaf spots with distinct dark purple margins that are easily diagnosed (Fig. 1). Overhead irrigation and rainfall help spread the pathogen throughout the field.  Cercospora beticola is most damaging in warm weather (day temperature of 77 to 90° F and night temperature above 60° F).

Controlling Cercospora leaf spot with preventative fungicide applications has become challenging for some growers in New Jersey. The pathogen is known to have developed resistance to important fungicide classes in recent years, such as the QoIs (FRAC code 11) and the DMIs (FRAC code 3) in different regions of the country, based on fungicide use. This is not surprising since resistance development can occur when fungicides in these groups are used extensively over many years. In New Jersey, azoxystrobin has been used extensively for years to manage this disease.

Cultural practices to help mitigate losses to Cercospora leaf spot

There are a number of cultural practices growers can do to help reduce losses to CLS.

  • Start with certified, disease-free seed, or treat seed using hot water seed treatment method.
  • Avoid fields with a known history of CLS.
  • Rotate to non-host crops (outside of the Chenopodium family) for 2-3 years.
  • Bury infected crop residues and destroy volunteer plants and weed hosts.
  • Burn down fields after harvesting.
  • Avoid planting succession crops close together (at least 100 meters apart).
  • Avoid overhead irrigation if it will result in prolonged leaf wetness periods (e.g., late evening or at night); irrigate early to mid-day when leaves will dry fully or use drip irrigation for small plantings.
  • Using the proper fungicides, rates, and fungicide rotations.

Fungicides for controlling Cercospora leaf spot

In recent years a number of new fungicides have been labeled for CLS control. Many of these fungicides contain two different active ingredients with more than one mode of action. Growers who have relied on managing CLS with azoxystrobin (FRAC code 11) for years and suspect a loss in efficacy should consider removing it from their fungicide program. There is a good chance fungicide resistance has developed. In 2019, a field study was done at RAREC to examine the efficacy of different fungicides for CLS control (Table 1). The fungicide efficacy trial was established in field with a  history of CLS; where the field was inoculated with infected debris collected from a farm in southern New Jersey. Fungicides were applied weekly for 5 weeks with overhead irrigation to help promote disease development.

Fungicide program (application timing) FRAC code active ingredient(s) Rate per acre Labeled for beet AUDPC value
Untreated control n/a n/a n/a n/a 617 a
Kocide 3000 (1-5) M01 copper hydroxide 1.0 lb Yes 564 ab
Quadris 2.08F (1-5) 11 azoxystrobin 15.5 fl oz Yes 538 bc
Fontelis 1.67SC (1-5) 7 penthiopyrad 30.0 fl oz Yes 510 bcd
Miravis Prime 3.34SC (1-5) 7 + 12 pydiflumetofen + fludioxonil 13.4 fl oz Yes 497 bcd
Merivon 2.09SC (1-5) 7 + 11 fluxapyroxad + pyraclostrobin 5.5 fl oz Yes 471 cd
Tilt 3.6EC (1-5) 3 propiconazole 4.0 fl oz Yes 445 d

 

Cercospora leaf spot development was extremely high during the course of the study. Area Under Disease Progress Curves (AUDPC) were calculated to determine the amount of disease development under each fungicide program (Table 1). CLS development was highest in the untreated control (UTC), with no significant differences between the UTC and weekly copper applications suggesting that weekly copper applications did not help reduce CLS in this study (Table 1). Weekly applications of Quadris, Fontelis, Miravis Prime were not significantly different, but significantly lower than the UTC (Table 1). Control of CLS was best with weekly applications of Tilt and Merivon, but these were not significantly different from weekly applications of Miravis Prime or Fontelis (Table 1). Results of this study suggest that growers with resistance concerns who have relied heavily on copper and azoxystrobin for CLS control should consider using other fungicides in their weekly preventative fungicide programs. Control programs should focus on applying fungicides with more than one mode of action and focus on rotating fungicides with different modes of action. For example: (please see 2020/2021 Commercial Vegetable Production Guide), Apply Tilt (FRAC code 3) followed by Miravis Prime (7 + 12), then tebuconazole (3), then Merivon (7+ 11), then Tilt (FRAC code 3), then Luna Tranquilty (7 + 9). Remember, resistance development to FRAC code 11 fungicides (QoIs) is qualitative and controlled by single point mutations, once resistance develops the fungus is completely resistance (to all fungicides in the group). Resistance development in FRAC code 3 fungicides (DMIs) is quantitative which often characterized as a gradual loss of resistance over time. As a note, FRAC code 3 fungicides should always be applied at the highest rate, using lower rates may increase selection pressure.

Organic Control Options

Controlling CLS in organic production systems starts by following and executing good cultural practices listed above. Always purchase certified seed. Use the hot water seed treatment method to help disinfested seed. Avoiding fields with a history of the disease. Producing beet on mulch and drip irrigation in small operations should be considered. This will help reduce weed pressure (as well as potential hosts) and reduce the need for overhead irrigation. Organic copper applications may not be effective in some operations where disease pressure is extremely high. Unfortunately, control of CLS with organic and biopesticides has been difficult, therefore good cultural practices must be followed accordingly.

 

Filed Under: Commercial Ag Updates, Vegetable Crops Tagged With: ,
January 9, 2020

Copper resistance in bacterial leaf spot found in New Jersey during 2020 growing season

Copper resistance has been detected in bacterial leaf spot of tomato and pepper and in Pseudomonas chicorii, the causal agent of bacterial leaf spot in basil, in New Jersey. While not surprising, copper resistance has been known to develop for decades now; however, this is the first time it has been confirmed in vegetable crops in New Jersey. Copper applications for the control of bacterial diseases in many crops has been a mainstay for decades now and is often applied in weekly protectant fungicide programs. In 2019 and 2020, with help from Dr. Nrupali Patel and Dr. Don Kobayashi, bacteriologists in the Department of Plant Biology located on the New Brunswick campus, a survey was begun to determine which species of bacterial leaf spot are most prevalent in New Jersey vegetable crops. Bacterial leaf spot can be caused by four species of Xanthomonas: X. euvesicatoria, X. vesicatoria, X. perforans, and X. gardneri. Currently, there are four races of BLS found in tomato (T1-T4; one for each of the 4 species stated above) and eleven races found in pepper (0-10). Differential tests in southern New Jersey using various bell pepper lines over the past 15 years has suggested that the number of races of BLS in pepper has increased over time; with all races present in the State to date. Lab testing results from samples collected from the small number of NJ vegetable farms the last two summers has shown the presence of X. euvesicatoria in pepper, as well as X. euvesicatoria and X. perforans in both tomato and pepper in the state, with ~50% of all samples testing positive for copper resistance.

How do you know what species of bacteria are present on your farm?

The only way to determine which species of bacteria are present in tomato or pepper crops on your farm are to have them identified through laboratory methods.

How do you know what races of the pathogen are present on your farm?

That’s a difficult question to answer. Up to now, the only way to know is through differential testing. That means planting a number of different bell peppers with varying BLS resistance packages and monitoring which cultivars develop symptoms. For example, if you detect BLS development in Aristotle X3R (which has resistance to races 1,2, & 3); then you possible have races 4-10 present on your farm. If you were to plant Turnpike in that same field and you have BLS development in it, then you possibly have race 6 or 10 present, because Turnpike has resistance to BLS races 0-5 and 7,8,9. It’s extremely important to know what races of BLS are present so you can chose the proper cultivars to grow. Choosing the proper cultivar will do two things: significantly reduce the chances of BLS development and significantly reduce the number of copper applications on your bell pepper crop. As a note, there are a few non-bell peppers available with BLS resistance packages (see 2020/2021 Commercial Vegetable Production Recommendations Guide).

How do you know if copper resistance is present on your farm? 

Growers who have used copper applications for controlling bacterial leaf spot in crops such tomato or pepper for many years should always monitor for efficacy. If you notice or have noticed a loss in copper efficacy over time, then there is a good chance copper resistance is present. Once copper resistance is detected, further applications will be unwarranted and ineffective. The only method to truly determine if copper resistance is present is through laboratory testing, however growers who pay close attention to efficacy should have a good idea if copper is still effective.

What can you do to mitigate bacterial leaf spot development on your farm?

In crops such as bell pepper, it comes down to growing cultivars with resistance to BLS and knowing what races are present on your farm. Many of the recommend commercial cultivars have varying resistance packages to the different races of the pathogen. Some cultivars, such as Paladin which has Phytophthora resistance has no resistance to BLS. Other “older” cultivars such as Aristotle X3R has resistance to races 1-3; newer cultivars such as Turnpike has resistance to races 0-5,7-9; while cultivars such as Playmaker and 9325 have resistance to 0-10 (also known as X10R cultivars). Unfortunately, BLS resistance in commercial tomato varieties are lacking, but efforts from around the world are making progress.

Moving forward in 2021.

More sampling and surveying are planned for the 2021 production season in New Jersey. Growers who are interested having tomato or pepper samples collected from their farm for species determination and copper resistance testing are encouraged to contact their county agent so arrangements can be made.

 

 

 

Filed Under: Vegetable Crops Tagged With: ,
January 7, 2020

Understanding and Controlling Tomato Brown Rugose Fruit Virus

Tomato Brown Rugose Fruit Virus (ToBRFV) is an emerging virus in greenhouse tomato production worldwide. The virus was first identified in Israel a few years ago and has since been found in Europe, Asia, Mexico, and the US.  The pathogen is known to be present in greenhouse tomatoes in Mexico, and has occasionally been found in field tomatoes grown there (UMASS); it has also been found on imported fruit in FL (Also see VGN story below). An outbreak was reported (and contained) in CA in early 2019 but, unfortunately, the virus was found in greenhouse tomato production in New Jersey this past fall.

ToBRFV is more severe on young tomato plants and can result in 30-70% yield loss (UFL). Foliar symptoms of ToBRFV on tomato and pepper include deformed, crinkled leaves, mosaic, mottling, flecking, chlorosis, and/or necrosis (see images). Fruit symptoms include discoloration and rough brown patches or ringspots. Irregular fruit shape and maturation patterns may also occur. Browning of the veins in the fruit calyx in the early stages of fruit ripening may also be observed. Symptom expression can vary widely among tomato cultivars (UMASS); while some green fruit may be infected but remain asymptomatic until the fruit starts to ripen.

ToBRFV is a member of the tobamovirus family along with tobacco mosaic (TMV), tomato mosaic (ToMV), and tomato mottle mosaic (ToMMV). ToBRFV is especially worrisome for tomato growers because it has overcome the Tm-22 gene that confers resistance to tobamoviruses in many tomato cultivars. Like TMV, ToBRFV is very stable and easily transmitted by mechanical means; in a highly managed crop such as greenhouse tomatoes, this means that human activity is the primary vector. The virus may also be transmitted mechanically by bumble bees employed to pollinate greenhouse crops. The virus can be seedborne and research indicates that it is associated with the seed coat, not the embryo. This means that treatments such as hot water or steam should be effective in removing the virus from seed (UMASS).

Management practices for ToBRFV include planting of disease free seed and seedlings, scouting plants regularly for symptoms, and isolating symptomatic plants. Disinfect tools and workers’ hands frequently. Recent research has demonstrated that the most effective disinfectants include 10% bleach, 50% Lysol, and 20% nonfat dry milk (UMASS). Currently, no commercial tomato varieties are tolerant to ToBRFV. Peppers with tolerance to TMV and pepper mild mottle virus (PMMoV) have shown some tolerance (MSU). ToBRFV’s high stability allows it to stay infectious in the soil, in plant debris and on stakes for long periods—up to 20 years. There are reports of spread by bumble bee pollinators in greenhouse situations. However, there are no reports of plant-to-plant transmission by aphids, leafhoppers or white flies (MSU).

There are no sprays that can be applied that are effective in helping to reduce the virus’s spread. Seed and transplant production are the most critical steps since contamination at these steps may create a risk of further contamination (MSU). A number of County Offices have the equipment for doing the hot water seed treatment method. Please contact your county agent for more information. Importantly, as a note, there is very limited to no information on infested seed sources, with only a few greenhouse tomato cultivars with known problems.

Recommended actions include (from MSU):

  • Start with certified clean or treated seed from a reputable dealer. Do not purchase seed from unverified sources, especially if they come from known restricted areas.
  • Have greenhouse workers wash and sterilize hands and tools often.
  • Supply single-use gloves that are discarded between greenhouse ranges.
  • Provide protective clothing that stays in that greenhouse range or that is well washed before going to another range.
  • Dispose of symptomatic plants and plants within 5 feet of infected plants. Also, dispose of plants, strings, trays and media through incineration—DO NOT spread it out on your fields (or reuse it for other crops in the greenhouse)!
  • Monitor movement of equipment and workers between fields. Thoroughly wash equipment and possibly have workers bring a change of clothes.
  • Rogue and incinerate symptomatic plants and conduct any daily activity last in that greenhouse followed by good sanitation.

On November 15, 2019, USDA/APHIS issued an emergency federal order that calls for pre-export testing of tomato and pepper propagative material (plants, seeds, grafts, and cuttings) and fruit produced in any country where ToBRFV has been detected; to date, this list includes Israel, Jordan, Turkey, Greece, Italy, the United Kingdom, the Netherlands, China, and Mexico. Countries where ToBRFV has not been reported may state this fact by providing a letter from the nation’s plant protection organization: propagative material and fruit exported to the USA will then be exempt from the testing requirement. Tomato and pepper fruit from Canada will also be subject to inspection prior to export, because Canada imports these crops from Mexico and re-exports them to the US. US Customs and Border Protection will also increase inspections at U.S. ports of entry to ensure imported tomato and pepper fruit from Mexico, Israel, the Netherlands, and Canada are free from symptoms of ToBRFV. (UMASS, USDA)

The NJDA, in cooperation with USDA APHIS PPQ, has been assisting affected NJ tomato producers in identifying critical control points and implementing the best management practices necessary to reduce the threat of introducing Tomato Brown Rugose Fruit Virus (ToBRFV) into future production. Tomato growers in New Jersey who suspect ToBRFV are encouraged to contact their county agent and the NJDA Division of Plant Industry. The NJDA is working with USDA APHIS PPQ to establishing testing protocols and will facilitate the screening of suspect plants.

References:

Dr. Anglela Madeiras (UMass)

http://ag.umass.edu/greenhouse-floriculture/fact-sheets/tomato-brown-rugose-fruit-virus-tobrfv

Dr. Ron Goldy (Michigan State University)

https://www.canr.msu.edu/news/tobrfv-a-new-concern-for-tomato-and-pepper-producers

Kendall Stacy (University of Florida)

http://blogs.ifas.ufl.edu/pestalert/2019/07/23/tomato-brown-rugose-fruit-virus/

American Seed Trade Association

https://www.betterseed.org/wp-content/uploads/ToBRFV-QA.pdf

USDA/APHIS

https://www.aphis.usda.gov/aphis/newsroom/stakeholder-info/sa_by_date/2019/sa-11/tomato-brown-rugose-fruit-virus

Vegetable Grower News – Tomato Brown Rugose Virus Concerns Growers

Filed Under: Commercial Ag Updates, Vegetable Crops
November 7, 2019

6-Week Urban “Annie’s Project” Farm Management & Business Training Course

Especially aimed at NJ farm women and veterans, Rutgers Cooperative Extension (RCE) will present a new, urban-focused version of the popular Annie’s Project titled “Farming in New Jersey’s Cities and the Urban Fringe.” Classes will be held simultaneously in Roseland, New Brunswick and Cherry Hill on Dec. 3, 10, 17 and Jan. 7, 14, 21, between the hours 6 – 9 p.m. Registration is currently open and is $150 until Dec. 2. Dinner will be provided at 5pm each evening of the class. [Read more…]

Filed Under: Commercial Ag Updates, Fruit, Vegetable Crops
October 10, 2019

Gramoxone/paraquat Mandatory Training Required Before Use

Spraying for pests

All pesticide certified applicators must successfully complete an EPA-approved training program before mixing, loading, and/or applying paraquat.

Anyone using Gramoxone, Firestorm, Helmquat, Parazone, and other paraquat products must complete an EPA-mandated training before application.

After November 14, 2019, the EPA requires companies to have newly labeled products on the market.

 

The following are items related to the new label for paraquat products:

  • Only certified applicators, who successfully completed the paraquat-specific training, can mix, load or apply paraquat.
  • No longer allow application “under the direct supervision” of a certified applicator.
  • Restricting the use of all paraquat products to certified applicators only.
  • EPA required Online Training – users must create an account with username and password.
  • A certificate will be delivered by the end of the training after successful completion of the online exam.
  • Applicators must repeat training every three years.

For additional information and FAQs about the paraquat training go to the EPA Paraquat Training website

Filed Under: Blueberry, Commercial Ag Updates, Fruit, Landscape, Nursery, & Turf, Organic Production, Tree Fruit, Turf, Vegetable Crops, Wine Grape