Changes Coming for the Use of Chlorothalonil (Bravo®) Products

By Jill MacDonald, Perennia Research Associate

Chlorothalonil is a contact and protectant fungicide that controls a broad range of fungal diseases. It is used on a number of crops. Due to the recent re-evaluation of chlorothalonil by the Pest Management Regulatory Agency (PMRA) there are changes that will affect how growers use the product, in relation to how it is mixed, loaded and applied. The re-evaluation has caused a discontinuation of Bravo 500 and Ridomil Gold SL/Bravo Twin-Pak formulations. The final day that these products will be available for purchase is May 10th, 2020, and the final day that growers will be able to make applications of these products is May 10, 2021.  After this time, it will be the responsibility of the grower to properly dispose of any leftover product.

How will these changes affect how I use chlorothalonil products?

Changes to Number of Applications Permitted

There have been several changes made to the number of applications that are permitted on fruit and vegetable crops, it is important to check how your crop is affected. The full list of changes, including application rates and REIs can be found here.

A few of the crops that are undergoing changes to the number of applications permitted per season:

Crop	2019	2020
Blueberry (HB)	3	2
Cabbage	5	2
Celery, field	9	2
Cherries (sweet and sour)	4	3 (2 spring + 1 post-harvest)
Cole Crops	5	1
Cranberries	3	1
Cucurbit Vegetables	7	2
Onion, dry bulb	3	2
Onion, green bunching	5	2
Peach, nectarine	4	3 (2 spring + 1 dormant)
Potato, table	12	3
Tomato (not for processing)	9	2
Wheat	3	2

Additional PPE, Buffer Zone Changes and REI

New requirements have been put in place to protect the applicator and persons who are handling the product, by increasing the amount of personal protective equipment (PPE) required. It is recommended to read the revised product label to obtain information on PPE and changes to the buffer zone requirements and restricted entry intervals (REI) for certain activities. Growers are reminded to have the updated label available to staff members who may come in contact with the product, as well as making them aware of the changes.

Implementation of Vegetative Filter Strips

Use of chlorothalonil requires a 10 meter (32’) vegetative filter strip (VFS) to be planted, if there is an aquatic ecosystem downhill from the field or sprayed area. A VFS is different than spray buffer zones: the filter strip is typically perennial, hardy, deep-rooted native vegetation that can slow runoff and filter out any pesticides that the runoff may contain. 

  

Figures were obtained from: https://www.syngentaebiz.com/dotnetebiz/imagelibrary/Vegetative_Strip_ECU_Bulletin_2019.pdf?utm_source=pardot&utm_medium=lp&utm_campaign=895&utm_content=en

Introduction of Closed-system Transfer

The PMRA will now require growers, under certain circumstances, to use a closed-transfer and application system. The closed-system transfer specifically focuses on mixing and loading of the product. All potato applications, or any applications when more than 340 kg a.i. are handled in one day will be subject to these requirements.  When product is directly transferred from the tote to the sprayer tank, this will now require dry poppet connections which comply with closed-transfer. Dry poppets are available from several manufactures and are also known by several names, such as dry poppet couplings or valves. Syngenta currently supplies a female dry poppet to male cam lever adapter with each tote of Bravo Zn. Many chemical handling systems and sprayers are fitted with cam lever connections from the factory, in this case you can purchase a dry poppet to cam lever adapter. The existing dry poppet valves on the 450L totes of Bravo®ZN are already compliant with the closed-system transfer requirement and will not need to be altered.

Figures were obtained from: https://www.syngentaebiz.com/Media_Upload/Pdfs/SY_19_WhitePaper_BravoZNClosedSystem_R3.pdf?utm_source=pardot&utm_medium=lp&utm_campaign=895&utm_content=en

Additional Important Changes

Hand harvesting of processing tomatoes and application through irrigation systems on strawberries and cucurbits (cantaloupe, muskmelon, honeydew, squash, pumpkin, watermelon and cucumber) is now prohibited.

For further details, please visit Syngenta.ca.

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Onion smut

Fig. 1. Infected leaves can become
bloated and split open, releasing spores
and contaminating the surrounding
soil.  Photo taken early August, 2019.

Onion smut only infects Alliums, and is a disease that can lie dormant in the soil for 15+ years, even in the absence of a host crop.  A cold spring such as we had this year results in the onion flag leaf emerging slowly, increasing the likelihood of smut infecting the onion.  The smut fungi can only penetrate and infect young seedlings - if the cotyledon escapes infection until it is mature, no further infection can occur despite high disease pressure. For this reason, healthy transplanted onions or onion sets typically avoid being infected by smut since they do not emerge in infected soils.  The infection period is from two or three days after the seed germinates until the first leaf is about three inches tall (about 10-21 days, depending on the year.)

Fig. 2. Black streaking on the onion bulb, August.

Early infections can result in seedling death, and plants that do survive will have characteristic black spots, blisters, and/or streaking (Fig. 1, 2).  Some infected plants will shed their outer leaves in the second month of growth, and continue growing, free of infection.  However, this year I'm seeing many infected plants that have survived the first few weeks of infection, and the smut fungus has continued to grow, systematically colonizing the plant.  These plants are are usually stunted.  Black pustules can infect as deep as the third or fourth scale (Figure 3).  Many infected plants will dry up, wither, and die by harvest.  Infected bulbs that do make it into storage shrink more rapidly, and are more prone to bacterial rots which can contaminate other bulbs in storage.

The causal fungi, Urocystis magica (synonym: U. cepulae) and U. colchici, can be transmitted from one field to another by surface drainage water, wind-blown soil, tools and farm equipment, soil in your shoe or truck treads, or any other method that transports soil.  Have you read Perennia's fact sheet about biosecurity in horticulture crops?

Fig. 3.  Smut infections penetrating several scales deep.

Long crop rotations are an important tool to limit the build up of disease in the soil.  Conventional growers that are planting into a known infected field should use seed treatments or an in-furrow fungicide application.  If organic or small-scale growers have a field history of onion smut, it is recommended to transplant onions into the field, rather than plant from seed in the infected soil.  Growers with smaller plantings should also remove and destroy diseased seedlings and plants to avoid building disease levels in the soil.

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Pest Update - Leek Moth

Perennia in association with NSDA and AAFC has been monitoring for leek moth across Nova Scotia since early May this year. Leek moth is an invasive insect pest from Europe that feeds on Allium species (onions, garlic, leeks,etc), and can cause significant damage to these crops. Previous to 2018, leek moth had been identified in Kings County in 2017. In 2016 gardeners reported damage on garlic which could have been due to leek moth but no specimens were ever recovered to verify these observations. In response to this a provincial leek moth monitoring project was established, to determine how widespread the pest is in Nova Scotia. As of this week we have confirmed leek moth in both Kings and Annapolis County. Currently we have not found the pest in large scale commercial fields, and all the leek moth samples we have identified have been from garlic. Leek moth favours garlic and leeks primarily; we are currently unsure of its effects in onion production.

Leek moth can be monitored using commercially available pheromone traps, which attract adult males. The adult leek moth is a small (5-7 mm in length) brown moth with a distinctive white triangle in middle of its wings when they are folded at rest. Additionally allium crops can be scouted for feeding damage from leek moth larvae. On alliums with flat leaves (garlics, leeks) the larvae feeds on the tops and inside of the leaves, as well as bores into the center of the plant leaving noticeable frass. In alliums with hollow leaves (onions, chives) the larvae will feed internally producing translucent areas on the leaf known as "windowing". The larvae will also occasionally bore into bulbs.

There are several chemical controls registered for leek moth in garlic, leeks, and onions that can be found in the Perennia's Garlic Management Schedule, Leek Management Schedule, and Onion Management Schedule. These pesticides are most effective when eggs are present and leek moth larvae are small, so monitoring is crucial to ensure proper timing of applications. Row cover is also an effective means of protecting allium crops against leek moth, without using chemical controls.

For additional information on leek moth identification and management please consult AAFC's An Integrated Approach to Management of Leek Moth . If you think you have leek moth please contact Matt Peill, horticultural specialist with Perennia (email: mpeill@perennia.ca, cellphone: 902-300-4710).

New pesticide registrations

Agri-Réseau is a resource available through The Centre de référence en agriculture et agroalimentaire du Québec (CRAAQ).  Every month, they publish a list of new phytoprotection registrations.  At Perennia, we are fortunate to have Mélanie Leclerc as part of our staff, and she has translated the March list of new pesticide registrations for Fruit Trees, Field Crops, Vegetables, Greenhouse, Berries, Ornamental, and "Other" (hops, hemp, quinoa, and basil), which can be found here.

From the Vegetable side, the main excitement is a few more weed control options in asparagus, Brassicas, and shallots, and some new disease management options in asparagus, kohlrabi, Brassica leafy greens, and bulb vegetables (Group 3-07A and 3-07B, so bulb onions, garlic, shallots, green onions, leeks, etc.)

Wireworms in Nova Scotia

Wireworms in transplants

For those of you who missed Dr. Christine Noronha's presentation on wireworms last week, you can find her presentation here. 

While many areas in Nova Scotia thankfully do not report wireworm problems, there are definitely high populations in some fields.  Last spring, we set traps in a few fields around the province.  Below is a graph from a vegetable field in Colchester County, showing high numbers of Agriotes sputator, one of the more voracious click beetle (adult wireworm) species.  Click beetle flight happens earlier in the warmer parts of the province such as the Valley.

Click beetle catch in Colchester County, 2016.

Perennia has set out some click beetle pheromone traps again this year, and we just collected our first sample.  Below is a photo of our first "haul" from Annapolis County.  On the left is A. obscurus, the middle is A. sputator, and on the right is A. lineatus.  Pheromone traps only attract males, so do not reduce the click beetle/wireworm population, but do give us a good idea of pest levels.  

May 23, 2017 click beetle catch from Annapolis County.

Wireworm updates

Dr. Christine Noronha is an entomologist with Agriculture and Agri-Food Canada in PEI with a particular interest in wireworms.  She will be visiting Nova Scotia this week and will give an overview of wireworms and their lifecycle (similar to last year’s presentation), as well as the most recent updates and highlights from her research into this pest. 

The presentation will take place at the Kentville Research Station (32 Main Street, Kentville) on Friday, May 12^th, 2017 at 9 am in the Perennia Training Room.  I know it’s a busy time of year, but we hope you can join us!