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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Understanding and controlling angular leaf spot in strawberries

Often considered a minor pathogen, angular leaf spot caused by the bacterium, Xanthomonas fragariae, can cause serious leaf and calyx infections ruining the marketability of fruit if left uncontrolled. Like all bacterium, the pathogen will infect leaves and the calyx through natural openings or wounds. Primary infections of new growth in the spring originate from systemically infected overwintered plants and dead leaves in which the bacterium survives the winter; or from infested transplants. The pathogen is very resistant to desiccation and can survive in old, dried leaves or infected plant debris buried in the soil. The pathogen will not survive free in the soil so it originates primarily from infected leaf debris and infected crowns.

Fig. 1. Water-soaked lesions caused by angular leaf spot on infect strawberry leaf. Photo by P. Nitzsche

Infections can often start in production operations and come in on infected bare root transplants or cuttings. Symptoms on leaves include initial small, irregular water-soaked lesions (Fig. 1). Young, actively growing leaves are most susceptible, especially on vigorously growing plants. Disease development is favored by moderate to low daytime temperatures, low night time temperatures – near or below freezing, and high relative humidity. Long periods of precipitation, overhead irrigation used to establish plantings or protect plantings from freezing, and heavy dews favor disease development.
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Cloth Face Coverings for Retail Employees: Executive Order No. 122

Cloth face masksThe Governor signed Executive Order No. 122 into law on Wednesday, April 8th.  This rule impacts retail sales locations that fall under the Executive Order No. 107 “essential retail business” category.  While many of the items would not be considered new, the requirement of cloth face coverings and gloves for employees is.

Face coverings for employees:
Workers are required to wear face coverings while at the retail location unless the covering would inhibit the individuals health.  Businesses are required to supply face coverings to workers.  The Executive Order does not acknowledge the fact that purchasing facemasks is currently very difficult.  The Executive Order does state that workers can supply their own face covering when preferred by the employee. Guidelines on how to make, wear, and handle face coverings can be found on the Rutgers On-Farm Food Safety COVID-19 webpage.   Printable signage is also available on the website.  Some community organizations are making cloth face coverings. These may be a resource for your workers who are not inclined to make their own if you are unable to provide them. Be sure to train your employees on proper use.  This face covering is not to be worn as a replacement for other personal protective equipment, such as those worn for pesticide applications.

Gloves for employees:
Businesses are required to provide gloves to employees who are interacting with customers and/or handling saleable goods.

Face coverings for customers:
Customers are required to wear cloth face coverings when they enter the retail area. When an individual refuses to wear a face covering for non-medical reasons the business should find an alternative method of shopping for the customer. Options could include pre or outside ordering with pick-up or delivery to the customer outside of the establishment.  Businesses may not ask for proof of a customers medical reason for not wearing a mask.

Visit the Rutgers On-Farm Food Safety COVID-19 webpage for updated resources relevant to your farm operation and COVID-19

Language specific to cloth face coverings and glove use from Executive Order No. 122 is below:

Essential retail businesses that are still permitted to operate under Executive Order No. 107 (2020) must adopt the following policies:
Require workers and customers to wear cloth face coverings while on the premises, except where doing so would inhibit that individual’s health or where the individual is under two years of age, and require workers to wear gloves when in contact with customers or goods. Businesses must provide, at their expense, such face coverings and gloves for their employees. If a customer refuses to wear a cloth face covering for non-medical reasons and if such covering cannot be provided to the individual by the business at the point of entry, then the business must decline entry to the individual, unless if the business is providing medication, medical supplies, or food, in which case the business policy should provide alternate methods of pickup and/or delivery of such goods. Nothing in the stated policy should prevent workers or customers from wearing a surgical-grade mask or other more protective face covering if the individual is already in possession of such equipment, or if the business is otherwise required to provide such worker with more protective equipment due to the nature of the work involved. Where an individual declines to wear a face covering on store premises due to a medical condition that inhibits such usage, neither the essential retail business nor its staff shall require the individual to produce medical documentation verifying the stated condition.

Identifying and controlling botrytis in high tunnel and greenhouse tomato production

Botrytis, or gray mold, caused by the fungus, Botrytis cinerea, can cause significant losses in high tunnel and greenhouse tomato production if not controlled properly. The pathogen can rapidly spread during periods when structures are closed and when relative humidity remains high for long periods of time. This often occurs when outside weather remains cool and damp while heating is needed. Gray mold is favored by temperatures from 64° to 75°F and requires only high humidity (not leaf wetness) to become established. The pathogen has a large host range and once established in an enclosed structure it can be very difficult to control (UMASS). The fungus can survive/overwinter as mycelia or sclerotia in plant debris and in organic soil matter (NCSU).

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Identifying and controlling leaf mold in high tunnel & greenhouse tomato production

Leaf mold occasionally appears in high tunnel or greenhouse tomato production in New Jersey. However, under ideal conditions the disease will develop in field-grown crops. The fungus will cause infection under prolonged periods leaf wetness and when relative humidity remains above 85%. If relative humidity is below 85% the disease will not occur. Therefore, the proper venting of high tunnels and greenhouses on a regular basis is important. The pathogen can survive (overwinter) as a saprophyte on crop debris or as sclerotia in the soil. Conidia (spores) of the fungus can also survive up to one year in the soil.

Symptoms of leaf mold on infected tomato plant. Note the bright yellow leaves and the olive-green spores developing on the undersides of leaves.

Symptoms of leaf mold on infected tomato plant. Note bright yellow leaves and olive-green spores developing on undersides of leaves.

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Identifying white mold in greenhouse & high tunnel tomato production

White mold, or timber rot, is caused by the soil-borne fungal pathogen, Sclerotinia sclerotiorum.

High tunnel tomato plant with main stem infected by white mold

High tunnel tomato plant with main stem infected by white mold.

The photo on right shows a high tunnel tomato plant with main stem infected by white mold. Over time the entire plant will slowly collapse looking similar to a wilt or root rot pathogen as the water supply is cut off to the plant.

White mold is common and once introduced into a field or high tunnel it can very difficult to control. The pathogen produces black sclerotia on the surface and inside infected stems. Sclerotia, if they make their way back into the soil, can survive for years causing significant problems.

Infected stems will turn a light brown color and dry up becoming brittle. If the main stem is infected the entire plant will collapse looking like a wilt or root rot issue.

Under hot, humid conditions white fungal growth will develop on the surface of the stems and in some cases sclerotia will develop on the outside of the stem. Breaking open the stem will reveal numerous black sclerotia.

All infected plants and or plant material need to be removed from the greenhouse or high tunnel immediately and disposed of properly. Preventative protectant fungicide programs beginning at flowering will help control white mold. Cool, wet weather and poor air circulation favors disease development.

There are a number of control options for conventional and organic growers listed in Table E-11 in the 2020/2021 mid-Atlantic Commercial Vegetable Production Recommendations Guide.

Tomato stem infected by white hold. Note the fungal growth on the surface of the stem.

Tomato stem infected by white hold. Note the fungal growth on the surface of the stem.

White mold of tomato. Note the black sclerotia developing inside the brittle stems.

White mold of tomato. Note the black sclerotia developing inside the brittle stems.

Allium leaf miner update: 04/09/20

Allium Leaf Miner

Allium leaf miner (ALM) adults were captured in higher numbers (16/week) on yellow cards in Princeton (Mercer Co.), NJ on Tuesday of this week, while lower numbers (2) were found near Milford, Hunterdon County.  Additionally, a garlic field near Asbury on the Warren/Hunterdon border was found to have 64% of plants exhibiting feeding/egglaying scars.  This indicates that the first (spring) flight of these flies is now in full swing, and damage is ongoing.  ALM flies were observed on foliage in all fields that were inspected this week.

Oviposition scars on onion

Photo: Sabrina Tirpak. Allium leafminer oviposition scars on onion

Growers should consider implementing the control method of their choice at this time.  Affected crops include chives, scallions, garlic, onions and leeks.

Floating row covers, kept on until this flight ends will help minimize access to plants.  Insecticide applications targeting adults may be helpful as well, although frequency of applications is uncertain.  Spinosyn materials (Radiant, Entrust (OMRI approved)), pyrethroids (Mustang Maxx, Warrior),  neonicotinoids (Scorpion, Venom) and the insect growth regulator Trigard are labeled for miner control.  The diamide, Exirel, is permitted in NJ under a 2ee label as well.

Adult activity and observations of feeding will be reported on in the IPM Update as they occur.  At this time, all growers should respond to the first adult generation.  We will attempt to identify the end of the first flight so that growers know when the risk of infestation has abated.