Fungicides/Bactericides

(Click here for pdf version of table)

Always read and follow label directions.  For copies of these labels, see the PMRA label search site at http://pr-rp.hc-sc.gc.ca/ls-re/index-eng.php or the manufacturer’s websites.

Watch for future postings summarizing recent insecticide registrations and herbicide registrations.  For updated herbicide registrations, you can also see the 2013 online update of the Guide to Weed Control at http://www.omafra.gov.on.ca/english/crops/pub75/pub75-revised-Feb2013.pdf (pdf 5.5 MB) and the April 19 post on the minor use registration of Command 360 ME for peppers.

OMAFRA’s Vegetable Crop Protection Guide (Publication 838), introduced in February 2012, is the source of pest control information for commercial field vegetable production in Ontario. The 2013 supplement, available online, lists updated registrations to December 2012.  Watch ONvegetables for the latest updates on pesticide registrations.

For information on minor use registration activity and issues in Ontario, visit OMAFRA’s minor use web pages at http://www.omafra.gov.on.ca/english/crops/minoruse/.

Arysta LifeScience North America and the Pest Management Regulatory Agency (PMRA) recently announced the registration of Kasumin® (kasugamycin) bactericide for several crops in Canada. This is the first registration for this active ingredient in Canada and marks an important milestone in addressing some of the most important diseases affecting pome fruit, fruiting vegetables and tree nuts. This product and the diseases it controls have been identified for many years as an important disease management tool needed by Canadian producers.

Kasumin® bactericide is registered for control or suppression of fireblight of pome fruits (apples, pears, quince), bacterial spot and stem canker of field and greenhouse fruiting vegetables (tomatoes, peppers, eggplant) and walnut blight of walnuts. The following table provides a summary of the crop registrations on the new Canadian Kasumin® bactericide label. Consult the full product label for detailed instructions, precautions and restrictions.

Follow all other precautions and directions for use on the Kasumin® bactericide label carefully. Consult individual crop and disease control recommendations on the Kasumin® bactericide label for additional use restrictions.

Kasumin® bactericide should be used in an Integrated Pest Management program and in rotation with other management strategies to adequately manage resistance. Consult provincial guidelines and local extension specialists for monitoring protocols and disease management recommendations.

We wish to thank the personnel of Arysta LifeScience North America, Agriculture & Agri-Food Canada, Pest Management Centre and US IR-4 Program for their support of this registration and the personnel of the Pest Management Regulatory Agency for evaluating and approving this important pest management tool.

For copies of the new Kasumin® bactericide label contact Jim Chaput, OMAFRA, Guelph (519) 826-3539 or visit the Arysta Canada website at http://www.arysta-na.com/ca-agriculture/products.html.

Note: This article is not intended to be an endorsement or recommendation for this particular product, but rather a notice of registration activity.

From ONvegetables in The Grower, April 2013

We often hear that most herbs can be used to repel pests in the garden, but herb growers know that they are susceptible to many pests as well. Unfortunately, there is very little information available to herb growers on pests and the strategies that can be used to control them. Just knowing what pests to look out for is half the battle, because it allows for pest control strategies to be implemented before pests become a problem.

Over the past two years, OMAF and MRA staff have been surveying culinary herb crops in southern Ontario to determine the major pests of herbs and eventually develop pest identification resources to assist herb growers. The project was initially funded through the OMAFRA/University of Guelph Undergraduate Student Experiential Learning Program, and summer student Alex Harris was hired to survey herb fields.

There are numerous culinary herbs that can be grown in Ontario, and most of them fall into two families: the mint family (e.g. mint, basil, rosemary, sage, lavender, oregano, thyme, lemon balm) and the carrot family (e.g. parsley, cilantro, dill, fennel, anise, chervil). Chives, tarragon, and fenugreek (methi) are the main herbs not included in these families. Insect pests tend to affect most of the herbs in a certain family, while diseases can be more specific to an individual herb.

Listed below are the major pests identified over the past few years:

INSECTS

Four-Lined Plant Bugs attack most members of the mint family. Since they lay their eggs on perennial plant tissues, they are not usually an issue on annual herbs such as rosemary and basil. Nymphs and adults pierce the leaves and stems with sucking mouthparts in June and July causing circular brown lesions. Affected leaves are often unmarketable. Insecticidal soaps used early when nymphs are small can reduce populations. Populations can also be reduced by controlling susceptible weeds and rotating mint-family herbs to different areas of the farm.

Four-lined plant bugs and damage on lemon balm

Leafhoppers are an important pest of virtually all herb crops. Many carrot-family herbs are susceptible to aster yellows, a mycoplasma disease transmitted by the aster leafhopper. Affected plants are distorted with multiple branches and are unmarketable. Leafhoppers cause hopper-burn, dieback of leaves from the tips, on several herbs, especially fenugreek (methi). Leafhopper feeding causes a stippling on leaves of most other herbs, which can reduce marketability, but rarely renders them completely unmarketable.

Japanese Beetles are a major pest of basil in certain areas of Ontario. The adult beetles emerge in late July and feed for 1-2 months at the top of the plant, causing ragged holes. They are more of a problem if basil is grown near a perennial grass, on which the immature grubs develop. Japanese beetle traps are available on the market but have not proven effective to control this pest and may actually attract more adults to the area.

Japanese beetles on basil

Two-spotted spider mites can be a significant problem on many of the mint-family herbs. Mites usually feed on the underside of leaves causing leaves to turn mottled and silvery. Fine webbing is usually present on the underside of the leaves. They are more of a problem in dry years when infested transplants are moved from a greenhouse to the field.

Other insect pests of herbs include aphids and garden fleahoppers (most herbs), leafrollers and spittlebugs (mint family), parsleyworms (carrot family), thrips (chives), and tarnished plant bug (most herbs). These pests do not occur in every year or field, but can build up to damaging levels, especially when large acreages are grown.

DISEASES

Basil downy mildew is a new disease in Ontario, first identified in the field in 2010. It appears as chlorotic (yellow) sections of the leaves defined by the veins, often with grey spores underneath. Once initial symptoms are found in a field the crop can be completely destroyed within a couple of weeks. Control of this disease is only possible through the use of a rotation of the registered pest control products Ranman and Confine. On-going research suggests that the cultivar ‘Medinette’ is slightly less susceptible to the disease than other cultivars. The disease may be delayed by growing basil in an open location with good airflow, with wider plant spacing.

Initial symptoms of basil downy mildew

Phomopsis has been identified on oregano/marjoram in Ontario and may also affect sage. Lesions develop on the leaves and stem, causing rapid senescence and collapse of individual stems. Little is known about this disease, and more research is required on its biology and management.

Septoria leaf spot is a significant disease on parsley in Ontario. It appears as round lesions on the leaves with small black specks (pycnidia). It usually affects the crop when extended dew periods occur, often later in the summer. It is especially a concern when the plants are weakened by another factor such as dry conditions, nutritional deficiencies, or root damage. Avoiding these issues will help to reduce the impact of the disease. An unrelated Septoria leaf spot also affects lavender, but has less impact on the crop because leaves of lavender are not harvested.

Septoria leaf spot on parsley

Bacterial blight often affects cilantro in Ontario. It is characterized by small circular lesions with a darker border. Bacterial diseases are usually spread by rain or irrigation-splashed spores or by machinery or field workers. Sanitation is important with this disease, since there are no products registered for its control.

Other significant diseases of culinary herbs include Phoma blight on dill, rust on mint, anthracnose on basil, powdery mildew on most mint-family herbs, and various Alternaria and Cercospora leaf blights on many mint and carrot-family herbs and fenugreek. Numerous soil-borne diseases also affect herbs, but in most cases have not been identified. Rhizoctonia and Fusarium are the most common fungi associated with crown and root rots. Root knot and root lesion nematodes also affect a wide range of herbs and can build up to significant levels if herbs are not rotated with unsusceptible hosts.

Management of pests of herbs is particularly challenging because few pest control products are registered for use on these crops. Growers should continually scout fields to identify problems before they get out of hand. Some pest issues can be more easily controlled at an early stage when they are isolated to one or a few plants. Sanitation, crop rotation, proper site selection, and fertilization are essential to reduce the chances of a pest developing to damaging levels.

OMAF and MRA staff are working on resources to assist growers with identification of these pests. Information on pests of culinary herbs along with photos of the significant pests are available in the new SPECIALTY CROPportunities module, which is now available on the OMAF Crops website. For more assistance with identification and management of herb pests, growers should contact an OMAF and MRA specialist.

Contact: Matt Sheppard, msheppard@bellnet.ca, tel:905-775-3317, fax: 905-775-3318

Conference Agenda

Wednesday Morning, April 3

Chair:  Matt Sheppard 

Wednesday Afternoon, April 3

Chair:  Jamie Reaume 

Thursday Morning, April 4

Chair:  Tom Miedema

Thursday Afternoon, April 4

Chair:  Peter Pauls

Bacterial disease is an annual problem in field tomato production in the Great Lakes region.  The diseases are difficult to manage and weather conditions often favour the disease over the crop.

There has been some concern that spray adjuvants could be helping bacterial pathogens to penetrate the protective layers of the tomato leaf or fruit, thereby contributing to disease problems.  Spray adjuvants, such as spreader-stickers, are added to the spray tank to improve the performance of certain pesticides.

At the Tomato Disease Workshop, held in Ohio in October, Dr. Sally Miller of Ohio State University presented the results of a study on the effects of adjuvants on tomato bacterial spot.

In this study, several bacterial disease control products were applied with or without a non-ionic surfactant.

This surfactant, Activator 90, is in the nonylphenol family, similar to products like Agral 90 or Ag Surf that are used in Canada.

Treatments were:

• Kocide
• Kocide + surfactant
• Cuprofix
• Cuprofix + surfactant
• Actigard
• Actigard + surfactant
• Actigard + Kocide + Kasumin
• Actigard + Kocide + Kasumin + surfactant
• Surfactant
• Kocide + Manzate
• Non-treated control

The lowest level of foliar bacterial disease was in the plots treated with Kocide plus Manzate, a standard treatment used by Ontario growers.  Disease levels were also lower than the untreated control in the Cuprofix, Cuprofix + surfactant, Actigard + surfactant, and Actigard + Kocide + Kasumin + surfactant treatments.  In most cases, disease levels with the surfactant added were numerically lower than disease levels without the surfactant, although the differences were not statistically significant.  When the surfactant was used alone, with no bactericide or plant defense activator, disease levels were not significantly different than the untreated control.

One might argue that these surfactants were applied with bactericides, and thus did not increase disease.  In Ontario tomato production, adjuvants would most often be used with certain herbicide applications, rather than with bactericides.  However, in the treatment where the adjuvant was applied alone, there was no increase in the level of disease. If the adjuvant was helping the pathogen to invade the leaf, this is where the difference should have really showed up, as there was no freshly-applied bactericide protecting these plants.

This research should reassure tomato growers about the use of adjuvants.  It is good to keep in mind that when a pesticide label specifies the use of an adjuvant, efficacy of the product could be compromised if it is not used as directed.  In some cases, there is essentially no efficacy without the use of the recommended adjuvant.

Bacterial spot lesions on processing tomato fruit

• Jim Jasinski, an assistant professor in Vegetable IPM from Ohio State University, will be discussing cucurbit disease control using conventional and air-assisted spray technology.

• Mary Gardiner, an assistant professor in entomology from Ohio State University, will be talking about natural enemies in the field. Some of the projects Mary has worked on under the Great Lakes Vegetable Working Group, include:
  • Flyer: Natural Enemies Identification http://glvwg.ag.ohio-state.edu/documents/NaturalEnemiesFlyer-FINAL.pdf
  • Video: Identifying and Enhancing Natural Enemies in Vegetable Crops http://www.youtube.com/watch?v=r1EYCevAgnY

• Rebecca Hallett, an associate professor and PhD. Candidate Braden Evans both from the University of Guelph, will give an update on recent work done on Swede midge management in both conventional and organic production systems. See what research has been happening on Swede midge. This pest is a serious insect pest for cole crops, which can be very difficult to control.

• Beth Gugino, an assistant professor in vegetable pathology from Pennsylvania State University, on the first day of convention will talk about disease management in high tunnels specific to vegetable production. The second day of the convention she will talk about soilborne diseases of vegetables and what to do about them, with focus on the use of cover crops.

Various speakers from Ontario will also give brief updates on Bacterial Disease Management in Tomatoes, Leek Moth in Ontario and Specialty Cropportunities, a new interactive, on-line tool which includes information on pest management for low acreage crops.

For more information and registration for the 2013 Ontario Fruit & Vegetable Convention, see http://www.ofvc.ca/.

Hope to see you there!

Crop symptoms are the obvious place to start. The more information you can gather the better. Try to catch the symptoms early.  It is almost impossible to accurately diagnose a completely dead plant! Look at both the leaves and the roots in several different locations in the field.

When collecting samples for disease diagnosis, include as much plant material as you can.  If a fertility problem is suspected, take soil and tissue samples from both the problem and unaffected areas of the field.  Unless otherwise specified, keep samples in the fridge or a cool location until they can be delivered to an agronomist or a laboratory.

Use the following list to help narrow down problem areas in your crop.  When talking to an agronomist, be sure to provide him/her with as much of this information as possible.

Symptoms:

1. What are the symptoms?  (yellowing, wilting, spots, insects, lodging, failure to emerge?)
2. When did they first appear?
3. Where do they occur on the plant (upper leaves, lower leaves, roots, stem?)
4. Where do they occur in the field (is there a pattern to the damage or is it randomly scattered?  Is it wide spread, or in an isolated section?)

Chemicals:

5. What has been applied to the field and when? This includes historical spray data for the previous 2-3 years.
6. Were tank-mixes or other tank additives used and are they compatible?
7. What were the weather conditions at the time of application?
8. What fertilizer products have been use and what was the rate and placement?

Sprayer:

9. When was the sprayer last calibrated and nozzles replaced?
10. When was the last thorough cleaning?  What chemicals have been used since then?

Seed:

11. Was it from a reliable, certified source?  How old was it?
12. What is the variety?  Are there any specific varietal susceptibilities or tolerances?
13. Was the seed treated?  With what?

Planting:

14. What were the weather conditions at the time of planting?
15. What was the planting depth?

Soil:

16. What are the soil test levels (including macro and micro nutrients)?
17. What is the pH?  Is this level compatible with any chemicals applied?
18. What is the soil texture and organic matter level?  Are these compatible with chemicals applied?
19. Does the soil structure or moisture differ in the affected areas? Is there a hard pan limiting root growth, water movement and aeration?

Environmental:

20. Any unfavorable weather conditions? (excessive heat, cold, dryness, wetness, winds, ozone/air pollution?)

With the hot, humid weather experienced in Ontario recently, cole crop growers should be vigilant at monitoring for black rot in cole crops this summer. Black rot is considered a serious bacterial disease of cole crops worldwide. Hot (25-30^oC), wet and humid weather favour the spread, infection and disease development in cole crops. Black rot is more severe and widespread in fields that either receive a frequent early morning shower or are overhead irrigated during this heat. Early prevention will protect the crop from late infections that provide wounds for other pathogens to infect, resulting in storage rot problems in late fall and winter.

V-shaped lesions containing black veins extending from the edge of a cabbage leaf along a major vein are typical black rot. First symptoms may appear as 1 to 3cm irregular, yellow areas along the edges of the leaves.

The pathogenic bacteria that cause black rot (Xanthomonas campestris) are often introduced into a field of cole crops on infected transplants but can also survive on cruciferous weeds during the summer and in contaminated crop residue left in or on the soil from previous years. At transplanting, the plants may not exhibit black rot symptoms due to environmental conditions.

Close-up of black rot lesion with blackened veins on Brussels sprout leaf.

These pathogenic bacteria are spread by rain splashing. In fact, black rot bacteria are highest during periods of rain. The bacteria enter through wounds caused by damaging winds, hail or insects as well as special pores on the edge of leaves called “hydathodes”. The disease spreads very quickly when bacteria-contaminated water droplets exude from theses hydathodes of infected plants and are rain-splashed to neighbouring healthy plants. Equipment, people, animals as well as overhead sprinkler irrigation can also spread the disease and result in significant losses.

There are no magic bullets available to control black rot in cole crops and disease management relies mostly on sanitation. The following are a few tips to help reduce the risk, spread and development of black rot.

• plant disease-free seed and transplants (3 infected seeds per 10,000 or 0.03% infected seeds can result in a black rot epidemic)
• 3 year rotation with non-crucifer crops  (cole crop residue takes about 2 to 3 year to completely break down)
• reduce plant densities to allow good air circulation and facilitate the quick drying of plants
• work in diseased fields at the end of the day (reduces the risk of spreading the disease to non infected fields on contaminated equipment)
• restrict activities in fields until later in the day when fields are completely dry
• control cruciferous weed hosts within and around the field (the pathogen can be water splashed up to 30 meters (~100 ft) from infected weeds to cole crop plants)
• insect management will help to reduce disease (wounds caused by insects provide an entrance for the pathogen)
• prepare crucifer crops for market away from fields and immediately chop and bury diseased tissue cut from plants
• grow black rot tolerant cole crop varieties whenever possible particularly in fields neighbouring those that were planted to infected cole crops the previous year
• do no apply excess nitrogen which encourages lush vegetative growth and can make the plants more susceptible to this disease
• scout fields regularly and remove all infected plants if possible from the field
• greenhouse sanitation is essential to produce seedlings that are free of black rot. Thoroughly disinfect all surfaces. Where black rot has been present in the greenhouse, discard and disinfect used trays.

Figure 1. Early Symptoms of Bacterial Wilt

Figure 2. Bacterial Wilt Infected Plant

The cucumber beetle spray threshold is 1 beetle per plant.  Inspect 100 plants across the field and divide the number of beetles by 100 to determine the average number of beetles per plant.  Cucumber beetles are most active in the early morning hours.  They often hide in the soil during the heat of the day.  Population assessments done in the middle of the day may not be representative of the actual number of beetles in the field.

For more information on cucumber beetles and bacterial wilt, visit Ontario Crop IPM at http://www.omafra.gov.on.ca/IPM/english/cucurbits/index.html

Bacterial Spot, Bacterial Speck in Tomato

¹ PHI = Pre-Harvest Interval (days)

For more information on Actigard and bacterial disease management in tomatoes, see New (and Old) Options for Management of Bacterial Spot and Speck in Field Tomatoes (April 2011).

Watch ONvegetables for other updates on vegetable pesticides.  These updates will be consolidated into a supplement to Publication 838, which will be available in the fall/winter of 2012.

9:00 am to 2:00pm

Room 405, 1 Stone Rd. W

Guelph, Ontario

To register call the Agricultural Information Contact Centre 1-877-424-1300 or email: ag.info.omafra@ontario.ca

* Lunch on your own

* Have to pay for parking at 1 Stone Rd. W location

Tuesday, May 22nd, 2012

10:00 am to 3:30pm

Woodstock OMAFRA Boardroom

Woodstock, Ontario

To register call the Agricultural Information Contact Centre 1-877-424-1300 or email: ag.info.omafra@ontario.ca

*Lunch on your own

Wednesday, May 9^th, 2012

9:30 am to 3:30 pm*

Wilson Hall Conference Room, University of Guelph– Ridgetown Campus

Ridgetown, Ontario

To register call the Agricultural Information Contact Centre 1-877-424-1300 or email: ag.info.omafra@ontario.ca

*Lunch on your own

Corn flea beetles are small (2 mm), shiny black beetles that move very quickly when disturbed.  Adult beetles feed on corn plants causing small circular holes or elongated scratch marks on the leaves.  The beetles typically emerge in mid-spring and populations peak in late-June.  Feeding injury rarely causes economic losses; however corn flea beetles are the primary vector of the bacterial disease, Stewart’s wilt.

Stewart’s wilt is a potentially devastating disease of sweet corn. It can cause yield losses ranging from 10-100%, depending on the time of infection and the variety.  When susceptible varieties are infected prior to the 5-leaf stage; the plants become wilted, turn brown and die. Later infections cause pale green or yellow stripes on the leaves, running parallel to the veins.  These plants remain stunted and often fail to produce a marketable cob.

There is a wide range of varietal tolerance for this disease. Dr. Jerald Pataky, University of Illinois, researches disease susceptibility in sweet corn varieties.  There is an extensive summary of his research at http://bit.ly/swtcrn-var-tol.  This article summarizes disease reactions of 800 commercially-available and pre-commercial hybrids since 1984. It also includes information on varietal tolerance for other important sweet corn diseases and herbicides.

The highly mobile nature of the corn flea beetle makes in-season control using foliar insecticides very difficult.  Where susceptible varieties are being grown, insecticidal seed treatments are a valuable tool to prevent losses due to this disease.  Systemic insecticides such as Gaucho 480 FL, Cruiser 5FS and Poncho 600 FS, provide good protection from flea beetle feeding during the early stages of crop growth.

The actual impact of the corn flea beetle and Stewart’s wilt on the 2012 growing season is yet to be seen. The mild winter is a concern.  However, the risk of infection will also depend on; the population levels leading into fall 2011, spring soil conditions and heat accumulation during the early growing stages. Where possible, avoid growing susceptible varieties for early and mid-season plantings. Where susceptible varieties are the preferred option, consider using a systemic seed treatment to prevent infection.

Bacterial Disease in Snap Beans.

Under field conditions, it is often difficult to distinguish between the three.  They all typically begin as small, water-soaked lesions on the underside of the leaves.

Occasionally a bright yellow spot on the upper leaf surface may be the first sign of infection. As the disease progresses the lesions expand and coalesce to form large, chocolate brown dry areas between the main veins of the leaf.  A thin yellow border often (but not always) surrounds affected areas.  For more infomation visit: http://www.omafra.gov.on.ca/english/crops/updates/vegetable/vcucbp20110707.htm

Always read and follow label directions.  This is not a complete list of registered products.

Newly transplanted tomato showing transplant shock

“Here’s a shot taken last week showing the transplant shock phase that tomato plants naturally go through before establishing in a field.  This occurs roughly five days after transplanting.  Leaves have a blue appearance.  Avoid spraying Actigard until the plant recovers out of this shock.  First Actigard application can begin 10 – 14 days after transplanting, and might best fit a full 14 day wait as plants are in cold wet soils this week, adding more stress to the plants at this time. Do not apply Actigard when plants are under stress.

If mixing Actigard with copper plus chlorothalonil:

• Fill the sprayer 2/3 full, begin agitation and add Actigard
• Add copper next
• Add chlorothalonil last and maintain agitation

Try to spray out the entire load at the end of the day and avoid letting the mix sit overnight in the sprayer as settling will occur.”

Actigard label (pdf)

Diseases such as bacterial spot and bacterial speck have been a major challenge in Ontario field tomato production for many years.  Management practices aimed at minimizing losses to bacterial disease begin in the greenhouse and continue through most of the season.

To review the greenhouse recommendation for tomato transplant production, a registered fixed copper bacteriacide should be applied according to label instructions, starting 2 ½ weeks after seeding, then every 5 days for a total of 5 applications.  Apply in sufficient water to wet foliage just to runoff, not to drench the plug.  This should be applied after the last watering of the day.

Field growers should ensure that their transplants have received the recommended copper spray program in the greenhouse.  In the field, start to apply the copper bacteriacide within 7 days after transplanting.  Apply at least 3 applications at 7-day intervals to keep bacterial disease from gaining a foothold in the crop.  This protects new growth and replenishes the greenhouse copper that is washed off by rain and dews.  If weather conditions are ideal for bacterial disease (ie. if there is a lot of wet weather), you may want to continue applications until early fruit set.

Growers’ decisions on extending the copper sprays may also depend on the end-use of the tomatoes (how many blemishes can be tolerated on the fruit) and if the plants are under other stresses that may weaken them and make them more susceptible to disease.

The key to this strategy is early prevention and control of bacterial diseases, before the population has a chance to build.  Since we cannot predict the onset or severity of bacterial disease, these early prevention and control strategies should be a part of your production system every year.  Once bacterial disease symptoms are present, it is too late to start to think about control.  Note, however, that most bacterial speck populations in Ontario are copper-resistant.

Many research trials across North America have shown that tank-mixing mancozeb with copper enhances bacterial disease control.   A new product for bacterial disease management, Actigard, has now been registered in Ontario, giving growers another tool to protect their crop.

How Does Actigard Work?  Actigard contains the active ingredient acibenzolar-S-methyl (ASM). ASM is a chemical that triggers the plant’s own defense system to produce proteins or structures that give the plant the ability to suppress pathogens that cause disease. Normally, these defense mechanisms are only triggered when the plant detects the presence of a pathogen. The reaction of the plant to applications of ASM is referred to as systemic acquired resistance, and is beneficial because the plant’s defense system is activated before an infection occurs.

Does Actigard Work?  Numerous trials have been conducted across North America and in most cases have demonstrated that Actigard is effective at reducing the severity of bacterial spot and bacterial speck on both processing and fresh market field tomatoes. For example, research completed in Ohio in 2001 demonstrated that spray programs including three applications of Actigard and five applications of Kocide + Dithane resulted in lower levels of bacterial spot symptoms on foliage than the nontreated control, whereas eight applications of Kocide + Dithane did not (Miller et al, 2002). In 2004 another trial completed in Ohio demonstrated that six applications of Actigard were more effective at reducing the percentage of diseased foliage than ten applications of Kocide + Manzate (Lewis Ivey et. al., 2005). Field evaluations of Actigard were also completed by Dr. Diane Cuppels at Agriculture and Agri-Food Canada in London, Ontario, in the late 1990s. The number of bacterial spot lesions on tomato leaves was 68 per cent lower than the nontreated control, and the number of bacterial speck lesions 29 per cent lower than the nontreated control (Louws et. al. 2001). Note that a number of these trials used different rates of Actigard than those on the approved Canadian label, and the spectrum of pathogens causing bacterial spot in Ontario is reported to have shifted to Xanthomonas gardneri (bacterial spot Group D) after this work was completed.

Will Actigard Cause Yield Losses?  Prior to using Actigard, it is important to thoroughly review the label. When you do this, you will notice that it contains a warning about potential yield losses. We reviewed several research reports summarizing yield data from over 45 field trials in North America, and a large majority of these trials reported no yield losses associated with applications of Actigard. In three cases, yield was lower than the standard treatments in the trial, and in one other case, yield was lower than the nontreated control.

Ideas for Incorporating Actigard into Your Bacterial Disease Management Program

• Consider Actigard as a supplement to current practices, as opposed to a substitute. Bacterial disease control remains challenging, and Actigard is likely not a silver bullet solution. Maintain diligence with your current bacterial disease management program.
  • Tank-mixing Actigard with a fixed copper product registered for bacterial spot and speck control will mean you are targeting the problem from two angles. Fixed copper directly targets the pathogens that cause disease, while Actigard boosts the plant’s defense system.
  • Use common sense and avoid applications of Actigard if stressful conditions are anticipated, such as herbicide injury, cold weather, or hail. These stress factors in combination with an application of Actigard may have negative effects on plant growth. It is also a good idea to wait until 7 days after transplanting before making an application of Actigard in order to avoid plant stress.
  • Actigard is not registered for greenhouse use.

A more detailed review on Actigard was presented at Tomato Day in Leamington.  The presentation can be found at http://www.opvg.org/tomato-day.aspx. For more information on tomato bacterial diseases, see the OMAFRA factsheet “Bacterial Diseases of Tomato” at http://www.omafra.gov.on.ca/english/crops/facts/05-069.htm.

As tomato transplanting begins, it’s a good time to review the strategy for bacterial disease management.

For the field grower, ensure that your transplants have received the recommended copper spray program in the greenhouse.  In the field, start to apply a registered copper fungicide within 7 days after transplanting – apply at least 3 applications at 7-day intervals to keep bacterial disease from gaining a foothold in the crop.  This protects new growth and replenishes the copper that is washed off by rain and dews.  If weather conditions are ideal for bacterial disease (wet weather), you may want to continue applications until early fruit set.

Growers’ decisions on extending the copper sprays may also depend on the end-use of the tomatoes (how many blemishes can be tolerated) and if the plants are under other stresses that may weaken them and make them more susceptible to disease.

The key to this strategy is early prevention and control of bacteria, before the population has a chance to build.  Since we cannot predict the onset or severity of bacterial disease, early prevention and control strategies should be a part of your production system every year.  Once bacterial disease symptoms are present, it is too late to start to think about control.

Many research trials across North America have shown that tank-mixing mancozeb with copper enhances bacterial disease control.

To review the greenhouse recommendation for tomato transplant production, a registered fixed copper fungicide should be applied according to label instructions, starting 2 ½ weeks after seeding, then every 5 days for a total of 5 applications.  Apply in sufficient water to wet foliage just to runoff, not to drench the plug.  This should be applied after the last watering of the day.

Notes:  Always read and follow label directions.  Most bacterial speck populations in Ontario are resistant to copper fungicides.

For more information on tomato bacterial diseases, see the OMAFRA factsheet Bacterial Diseases of Tomato.