Rutgers University | New Jersey Agricultural Experiment Station | Pesticide User Responsibility

March 9, 2023

Allium leaf miner update: 03/09/23

Allium Leaf Miner (ALM)

Allium leaf miner feeding and egg laying injury was reported on chives in southern Cape May County on Thursday.  The West Cape May weather station (closest station) has recorded 295 growing degree days (GDD) base 39˚F as of Thursday.  39˚F is close to the lower developmental temperature (38.3˚ F) which our colleagues at Penn State recommend for predicting the first emergence of ALM adults.  295 GDD at this temperature is in excess of the 250 GDD base 38.3˚ F that is the threshold for adult emergence and activity.   In recent years, initial feeding/egg laying scars have been detected within a few days of local weather stations recording the 250 GDD threshold.  Growers who feel they may be impacted by this pest should check the accumulated GDD from local weather stations.   Growers in southern counties may reasonably assume there will be ALM activity in their area soon, if not already happening.  To determine GDD from local weather stations, the NEWA website https://newa.cornell.edu/ is very helpful.  From the NEWA home screen, select the nearest weather station from drop down menu at the center of the page.  Next, scroll down to “Weather Tools” on the right side of the page, and select “DD Calculator”.  Select your start date (1/01/23) and end date as well as Degree Day Type (39 F) from the menu at the left of the page.  The site will automatically generate the accumulated GDD base 39F to the last day of your requested sample, and then offer a forecast of accumulated GDD for the next week.

Plant stem

Photo: Sabrina Tirpak. Allium leafminer oviposition scars on onion

Growers should consider initiating the control method of their choice at this time.  Affected crops include chives, scallions, garlic, onions and leeks.  Look for neat rows of white spots descending from the upper tips of allium leaves (see photo at left).  Initial injury often occurs on the tallest leaves.  Under warmer, less breezy conditions, adults may be seen near the tips of leaves (see photo of adult at lower right).

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, Spider on leafWarrior), neonicotinoids (Scorpion, Venom), the diamide Exirel (section 2ee recommendation) and the insect growth regulator Trigard are labeled for miner control.

Adult activity and observations of feeding will be reported on in the IPM Update as they occur.

 

 

 

Filed Under: Organic Production, Vegetable Crops Tagged With: , ,
July 16, 2022

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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Filed Under: Vegetable Crops Tagged With: , , ,
July 13, 2022

Collar Rot and Alternaria Stem Rot of Tomato

Collar rot (Alternaria linariae) or Alternaria stem rot (Alternaria alternata f. sp. lycopersici) of tomato are common in young tomato plants. Either can be particularly troublesome in seedlings that have been held in transplant flats for an extended period of time before transplanting in hot, humid greenhouses. Collar rot infections often start where a leaflet branch has been broken or pruned which allows a point of infection. Symptoms of Alternaria stem rot include brown circular to irregular lesions on stems with definitive concentric black rings (very similar to Early blight on infected leaves). Symptoms of Collar rot are similar and may or may not produce concentric black rings. Infections that start in the greenhouse may lead to losses in the field as stems become girdled causing the plant or branches to wilt and die. Most commercial tomato varieties have resistance to Alternaria stem rot. While resistance is lacking to Collar rot, growers should chose varieties with Early blight resistance. Fungicides used to control Early blight are also effective against Collar rot.

Symptoms of Collar rot in young tomato

 

 

Filed Under: Vegetable Crops Tagged With: ,
July 10, 2022

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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Filed Under: Vegetable Crops Tagged With: , , , ,
July 8, 2022

Recommendations for Under Plastic Mulch Weed Control

Plastic mulch, usually used with trickle irrigation, has many horticultural benefits for summer vegetable crops, and black plastic controls most annual weeds. Mulch does not solve all the weed problems in the field, and creates new challenges for the grower.
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Filed Under: Vegetable Crops Tagged With: , , ,
July 8, 2022

Update on Status of Dacthal Herbicide

DCPA (dimethyl tetrachloroterephthalate) is a selective preemergence herbicide used for control of annual grasses (foxtail, crabgrass, barnyardgrass, goosegrass, fall panicum) and some broadleaved weeds (purslane, common lambsquarters, pigweeds) in vegetable crops and ornamental turf. Commercial formulations of DCPA include Dacthal® Flowable herbicide. Dacthal® Flowable is labelled for use on the following vegetable and fruiting crop groups: cole leafy vegetables, seeded melons (cantaloupe, honeydew, watermelon), collards and mustard greens, horseradish and radish, onions, sweet potatoes, tomatoes and eggplants, strawberries.

  • What is happening with DCPA, the technical ingredient in Dacthal® Flowable herbicide from AMVAC?
    On April 27th the U.S. Environmental Protection Agency (EPA) published a notice of intent to suspend (NOITS) DCPA technical registration in the U.S. The basis for this action was that AMVAC had not provided multiple studies required during the registration review.
  • How did AMVAC and key grower stakeholders respond to this action by the EPA?
    According to FIFRA (Federal Insecticide, Fungicide, and Rodenticide Act), AMVAC and impacted stakeholders had the opportunity to
    appeal the NOITS within 30 days, which they did on May 27th. The purpose of the appeal was to obtain a hearing that would allow
    evidence from each side to be presented in front of an Administrative Law Judge (ALJ) appointed by EPA.
  • Did AMVAC and the grower stakeholders have the opportunity for a hearing?
    No. The assigned EPA administrative law judge (ALJ) ruled on Friday July 1st that the NOITS was upheld without requiring a hearing.
  • How will that impact end use formulated products like Dacthal Flowable herbicide?
    This decision does not impact formulated products (i.e., Dacthal Flowable). AMVAC’s customers can continue to sell, distribute, and
    apply Dacthal Flowable.
  • What happens now in this process concerning DCPA?
    The July 1st decision granted EPA the ability to suspend DCPA technical without requiring a hearing to examine AMVAC and
    EPA testimony. AMVAC will appeal this decision to the Environmental Appeals Board.
  • Is the registration of the end-use product Dacthal Flowable herbicide impacted by the NOITS?
    If you have used or plan to use end-use products containing DCPA, there are no consequences from that use or downstream
    consequence for the crop you applied it to, now or in the future, from NOITS activities. Applications of Dacthal Flowable end-use
    products remain legal and the established United States tolerances remain in place.
  • What are the next steps in this process? How will it impact the availability of Dacthal Flowable?
    AMVAC can continue to manufacture, sell, and distribute end-use products until notification of the appeal process has been completed. AMVAC’s customers can continue to sell, distribute, and apply Dacthal Flowable. AMVAC is commitment to continuing to exhaust all options to defend DCPA. Outside of any legal proceedings, AMVAC continues to generate and submit to EPA the data necessary to fulfill the Data Call-In (DCI) Notices required to complete registration review for DCPA, regardless of the suspension status.

 

 

Filed Under: Strawberry, Vegetable Crops Tagged With: , , , ,