HORT MATTERS 1 June 20, 2014

VOLUME NO. 14, ISSUE NO. 13 JUNE 20, 2014

IN THIS ISSUE... What is it?

Hort shorts

BMSB update

SWD update

Healthy soil +

Healthy roots =

wealthy yields

Healthy soils

webinar series

Thermal inversions

and spray drift

Spray coverage

field

demonstration

Use of Sandea

herbicide

HORT MATTERS OMAF and MRA Specialists in Horticulture and Specialty Crops.

Over the past week there has been increasing downy mildew activity in the Southern US. There are active infections present in Florida, Georgia, Louisana, Texas and the Carolinas. Late June is typically when infections start occurring in the Great Lakes basin.

Scout all cucumber fields regularly for signs of downy mildew. Begin a preventative fungicide spray program no later than vine development. Start the spray program earlier if cool wet weather conditions, or strong storm activity persists.

You can follow cucurbit downy mildew activity across North America on the ipmPIPE website: www.cdm.ipmpipe.org.

Broadspectrum, preventative fungicides include:

mancozeb (Dithane Rainshield, Penncozeb 75DF and Manzate Pro-Stick)

chlorothalonil (Bravo 500) As soon as downy mildew is identified in the Great Lakes region, switch to a targeted downy mildew fungicide. These include:

cyazofamid (Ranman 400SC or Torrent 400SC)

propamocarb/chlorothalonil (Tattoo C)

ametoctradin/dimethomorph (Zampro)

Fluopicolide (Presidio) The new Ontario Vegetable Crop Protection Guide (Publication 838) has a full list of cucurbit downy mildew fungicides. It is available at:

regional OMAF/MRA offices

online at ServiceOntario Publications website at www.ServiceOntario.ca/publications.

by phone: ServiceOntario Publications Contact Centre at 1-800-668-9938 or 416-326-5300 or TTY 1-800-268-7095 from 8:30 am to 5:00 pm, Monday to Friday.

Cucurbit downy mildew update – June 18 Elaine Roddy, Vegetable Crop Specialist

ISSN 2291-6121

Downy mildew on cucumber leaves

HORT MATTERS 2 June 20, 2014

COMING EVENTS

July 9th, 10th, Southwest Crop Diagnostic Days, Ridgetown.

Register online by June 30th at: www.diagnosticdays.ca/

July 17, Ridgetown Vegetable Open House, Ridgetown area,

hosted by OMAF & MRA and Ridgetown Campus – University

of Guelph. Commercial vegetable growers and

agribusiness mark your calendars! More details to come on

times and tour locations. Choose an afternoon or evening

tour. No cost. No preregistration required. Watch for more

details soon.

July 29, Ontario Apple Growers Tour, hosted by the Georgian

Bay Fruit Growers and the Ontario Apple Growers.

Mark your calendars – details will follow about tour stops and

featured presentations.

August 20 & 21, North American Strawberry Growers

Association Summer Tour, British Columbia. For more

information visit www.nasga.org.

August 21, Ontario Potato Field Day, HJV Equipment, Alliston

Feb 3-6, 2015, North American Strawberry Growers

Association Conference and Symposium, Ventura, California.

The NASGA Symposium is only held once every 4 years so

hope to see you there. For more information visit

www.nasga.org.

EDUCATIONAL EVENTS:

Arboriculture and Landscape Professionals: ISA Workshop:

“IPM in the Woody Landscape”. Tuesday, July 15 at the

University of Guelph Arboretum Centre. Come spend the day

learning about current pests and physiological problems on

trees and shrubs. This workshop will be led by Jen Llewellyn

with Dr. Shannon Shan and Sean Fox. CEU’s are availa-

ble! To register, contact Kathleen at ISA Ontario at 1-888-

463-2316 or info@isaontario.com

Growers: Nursery Growers Research Auction, Wednesday,

July 16 at Winkelmolen Nurseries. Landscape Ontario’s

Growers Group invites you to its annual fundraising auction

No admission fee or RSVP required. Bid on top quality plant

material and tour the production farm while helping raise

funds for industry research and scholarships. All winning

bidders will be entered into a draw for a special prize. Enjoy

lunch, network with peers and bid on fantastic items –

something for everyone!

Farm Tours: 10:00 a.m. – 11:30 a.m.

Lunch and Refreshments: 11:45 a.m. – 12:45 p.m.

Live Auction: 1:00 p.m. – 4:00 p.m.

Subscribe on-line to receive notice by email when a new issue of Hort Matters is posted. All you need to do is enter your email address at http://www.omafra.gov.on.ca/english/subscribe/index.html and submit.

To receive a fax version of Hort Matters, send your fax number to: OMAF and MRA, Vineland Resource Centre, Box 8000, 4890 Victoria Avenue N, Vineland Station, ON L0R 2E0 or fax to 905-562-5933.

Edited by: Hannah Fraser, Entomology Program Lead (Hort)

Prepared by: Carolyn Prieur, Client Service Rep, Vineland Resource Centre

Horticulture Technology Mike Celetti Pathologist 519-824-4120, x58910 Jim Chaput Minor Use Coordinator 519-826-3539 Hannah Fraser Entomologist 905-562-1674 Kristen Obeid Weed Management 519-738-1232 Christoph Kessel Nutrition 519-824-4120, x52480 Deanna Németh Nutrient Management Planning Spec. 905-562-1170 Anne Verhallen Soil Management Specialist 519-674-1614 Vacant Organic Crop Production 519-826-4587 Denise Beaton Crop Protection Program Lead 519-826-6594 Jason Deveau Application Technology Specialist 519-426-8934 Horticulture Crops Marg Appleby IPM Systems Specialist 613-475-5850 Eugenia Banks Potato Specialist 519-826-3678 Wendy McFadden-Smith Tender Fruit & Grape IPM Spec. 905-562-3833 Jennifer DeEll Fresh Market Quality 519-426-1408 Pam Fisher Berry Crop Specialist 519-426-2238 Janice LeBoeuf Vegetable Specialist 519-674-1699 Elaine Roddy Vegetable Specialist 519-674-1616 Kathryn Carter Tender Fruit & Grape Specialist 905-562-1639 Leslie Huffman Apple Specialist 519-738-1256 Kristy Grigg-McGuffin Pome Fruit IPM Specialist 519-426-4322 Marion Paibomesai Vegetable Crop Specialist 519-826-4963 Greenhouse, Agroforestry & Specialty Crops Jim Todd Transition Crops Specialist 519-426-3823 Melanie Filotas Specialty Crops IPM Specialist 519-426-4434 Sean Westerveld Ginseng & Medicinal Herbs Spec. 519-426-4323 Evan Elford New Crop Development Specialist 519-426-4509 Wayne Brown Greenhouse Floriculture Specialist 905-562-4141, x179 Graeme Murphy Greenhouse Floriculture IPM Spec. 905-562-4141, x106 Shalin Khosla Greenhouse Vegetable Specialist 519-738-1257 Gillian Ferguson Greenhouse Vegetable IPM Spec. 519-738-1258 Pam Charbonneau Turfgrass Specialist 519-824-4120, x52597 Jennifer Llewellyn Nursery Crops Specialist 519-824-4120, x52671 Todd Leuty Agroforestry Specialist 519-826-3215 Mahendra Thimmanagari Crop Bioproducts Specialist 519 826-4593

http://www.ontario.ca/crops

OMAF and MRA STAFF

working for you

Suggestions? We’d like to hear from you

Hort Matters, OMAF and MRA, Box 8000, 4890 Victoria Avenue N,

Vineland Station, ON L0R 2E0 Ph. 905-562-1674 Fax 905-562-5933

Email: hannah.fraser@ontario.ca

HORT MATTERS 3 June 20, 2014

HORT SHORTS - June 17

Soils in many areas in the southwest are becoming dry. A gentle

rain would be welcomed by many. However, some areas east of

Toronto have experienced heavy rains ranging 1-5”, and are

looking for drier conditions.

Apples: Apple fruitlets are quickly growing past the chemical

thinning window. Some touch-up hand thinning will be needed,

but in general the cool spring and aggressive thinning appears

to have reduced the cropload to better levels. Some blocks have

disappointing return bloom, eg. Honeycrisp and Golden Deli-

cious. Winter injury is becoming more evident in Mutsu, Jonag-

old, Fuji and Golden Delicious, and surprising some older and

healthy trees are dying. Hot weather and dry conditions this

week may hasten their demise. Scab lesions have been ob-

served on fruit and fire blight is present in some orchards. Spray

timing for codling moth has passed in most regions and OBLR

biofix has been set. Scale crawlers are expected to begin emerg-

ing shortly and leafcurling midge are beginning to pupate in the

earlier regions. European apple sawfly, plum curculio, mullein

bug and plant bug damage can be found on developing fruitlets.

Mite populations are slowly starting to build.

Berries: Strawberry harvest is in progress mostly from day neu-

tral plantings and early June varieties if row covers were used.

Pick your own will open soon. Plan on lots of strawberries for

Canada day and a nice long late strawberry season.

Cyclamen mites are common. Sap beetles have already been

reported as a fruit pest at one site. Virus symptoms are contrib-

uting to some very poor plant stands with missing or stunted

plants. Fields which were not sprayed for aphids in 2013 seem

especially bad.

Vegetable: Asparagus harvest is winding down and it is time to

make post-harvest residual herbicide control choices. Rust is

present in nursery and immature fields. Early peas are coming

on fast. Early melons are starting to flower and zucchini harvest

has started.

Specialty crops: Alternaria leaf and stem blight is still the big-

gest issue in ginseng at this time. Growers need to scout regu-

larly for the first signs of disease, apply a rotation of fungicides,

and ensure thorough coverage of all above ground surfaces of

the plant. Lavender is about to begin blooming in the south-

west. Bloom will be staggered this year with shoots off of old

stems blooming first and new shoots blooming later. Four-lined

plant bug damage continues to be reported in many areas, and

will also be present on most other mint-family herbs (e.g. thyme,

oregano, sage, lemon balm, savory). Basil downy mildew has

now been reported in potted basil throughout Ontario. Field

growers need to keep plants protected from airborne spores.

Nursery and Ornamentals:

In the north Toronto area, there is quite a problem with yellow

headed spruce sawfly. I blogged about their hatch last week

and already they have grown to 10-15 mm long! Take a quick

scan of the new growth on spruce, especially Colorado spruce

(Picea pungens). Look for straw-like needles that are wither-

ing….and the disappearance of needles all together. This is very

typical damage of YHSS.

?

Test your

horticultural

knowledge

Last week we asked what these are found under the bark of grapevines.

nswer: Grape mealybugs can be found under

the bark of vines. The nymphs and the adult fe-males have a flattened, oval pink body covered in a mealy white wax coating. Mature females are 4- 5 mm long, with long waxy filaments along the rear end. Or-ange eggs are laid in cottony masses; the yellow to brown “crawlers” that emerge are not covered in wax. We are currently finding predominantly adults so the second generation will be starting any time. One aspect of interest with respect to grape leafroll virus is the biology of the vectors (mealybugs and scales). In order to study this, we are monitoring in four vineyards (two in Lincoln, two in NOTL) where grape leafroll disease was confirmed in the survey conducted in the fall of 2013. In order to confirm the species of mealybugs, we would like to sample a large number of vineyards across On-tario. We will collect insects and send them off for identification. If your vineyards had symptoms of leafroll disease last fall and you are interested in participating in this research, please send an email to wendy.mcfadden-smith@ontario.ca.

For more information refer to a previous Hort Matters article, Mealybugs, scale oh my” www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2014/09hrt14a2.htm.

Con’t on pgs 8 & 10

HORT MATTERS 4 June 20, 2014

Healthy soil + healthy roots = wealthy yields Laura L. Van Eerd and Steven Loewen, Ridgetown Campus, University of Guelph

We know the value of a good soil and a healthy root system. This was evident in the summer of 2009, when processing tomato growers in southwestern Ontario noticed unusual crop symptoms, which resulted in an estimated 30% or higher yield loss in some fields. This came to be known as ‘vine decline complex’ and appeared to be due to mix of several root diseases. This makes management challenging because conditions that suppress one fungus may amplify others. While plant breeder Steven Loewen worked on developing resistant varieties, Prof. Laura Van Eerd decided to take an alternative strategy. Her approach was to focus on the soil and test a variety of soil amendments. The hope was that these treatments might promote healthier bacterial and fungal populations in the tomato root zone thereby tipping the balance to healthy plant roots and good tomato yields.

Field trials were conducted in commercial processing tomato growers’ fields from 2011 to 2013, in a total of 4 locations. Fields with a high incidence of vine decline complex were selected. Soil amendments were applied in the spring and incorporated into the soil, with tomatoes being transplanted two to three weeks later. Growers followed their typical management production practices for fertility and pest management.

In all growing seasons and locations, soil amendments of poultry manure, mushroom compost, thermophilic compost, and MPT MustGRO® mustard seed meal gave equal or higher yields of processing tomatoes than the unamended control. In all years, poultry manure had greener, lusher plants and delayed maturity, likely due to the extra nutrients provided by the manure. Based on plant growth and soil testing, researchers do not believe that the yield increases with soil amendments were strictly due to nutrients.

Work is underway to gain a better understanding of the microbial community in and around tomato roots. Researchers at Ridgetown Campus and A&L Canada Laboratories in London, Ontario, are continuing to work together to learn more about the vine decline complex and how to manage it. The positive results from these trials are providing optimism for future breakthroughs.

So, why did the soil amendments improve tomato yields? Perhaps, the carbon in the amendments provided food for the microbes and good soil conditions for growth and a healthy root system, which lead to good crop yields. It is speculated that the soil amendments changed the type of microbes around the root to the advantage of tomato yield. Thus, practices such as soil amendments that appear to improve soil and root health provided an advantage to crop yields.

Researchers are grateful for the valuable assistance from growers and ConAgra Foods Canada INC. in Dresden; project funding by Ontario Tomato Research Institute, and the Ontario Ministry of Agriculture and Food and Ministry of Rural Affairs.

Healthy Soils Webinar Series from USDA-NRCS

Managing for Soil Health when Raising Potatoes: A Farmer’s Perspective Brendon Rockey, Rockey Farms, LLC, San Luis Valley, CO

Presented by the: USDA NRCS National Soil Health and Sustainability Team, East National Technology Support Center

July 8, 2014

2PM Eastern / 11AM Pacific (60 Minutes)

Learn more about this webinar at campaign.r20.constantcontact.com/render?ca=687ed22f-c13d-4507-9f4e-92a091a2c1ae&c=b7f2d7a0-7ce4-

11e3-9813-d4ae52754950&ch=b8cd8030-7ce4-11e3-987a-d4ae52754950

See the full list of webinars in the series at archive.constantcontact.com/fs140/1109295883063/archive/1115970610330

HORT MATTERS 5 June 20, 2014

A team of OMAF staff and students together with 12 scouts and consultants from agribusiness and research , are monitoring for SWD in Ontario in 2014. We are planning to have apple cider vinegar traps set up at 50 key locations between Essex , Ottawa, Niagara, Georgian Bay and New Liskeard. Thanks to the Ontario Berry Growers Association and OFIP 2 funding we have a student placed in eastern Ontario to focus on SWD and have hired an assistant in Guelph to help process trap contents.

WE have trapped SWD in 1 location. This was an early trap capture (June 3) of one female fly in a strawberry field east of Toronto. We have not caught SWD at this site since then and do not think that fruit is at risk at this time. Our neighbours in New York and Michigan are not reporting SWD either. Growers and consultants who are who are monitoring for SWD themselves should have early trap captures verified – we are happy to do that for you. Remember that traps may not be sensitive enough to catch the first SWD on your farm – use regional counts (combined from several locations in a region) to make your spray decisions.

Fruit assessment is an important tool for monitoring SWD

When ripe fruit is present, and flies are active in the region, insecticides as well as other management practices are needed for control.

New : Insecticides have been registered for SWD control in 2014. See: www.omafra.gov.on.ca/english/crops/facts/swd-registrations.htm

Visit www.Ontario.ca\spottedwing for weekly updates on SWD activity in Ontario

SWD UPDATE

Eggs being laid, nymphs emerging soon

BMSB adults are still being found indoors, although most will have made their way outside by now. Apart from an adult female collected at one of our hot spots in Hamilton a few weeks ago, BMSB have not been found during our provincial surveys. Numbers will remain low and populations difficult to detect until BMSB begin to lay eggs and nymphs emerge. However, the female specimen we collected a few weeks ago at our hot spot has laid an egg mass and the nymphs are about to emerge. This means that adults were present, sexually mature and mating as early as late May – much earlier than the developmental model for BMSB would predict for southern Ontario. While a sample size of 1 is not exactly a strong data set, it’s a head’s up to growers and their scouts. If you haven’t started monitoring in your crops (peach is an early crop host) and in landscape along crop borders (buckthorn, lilac and Tree of Heaven are good early wild hosts) , consider doing so now.

The research team conducting surveys in crops and landscape hosts across southern Ontario (Cynthia Scott-Dupree, University of Guelph, Tara Gariepy, Agriculture and Agri-Food Canada, Hannah Fraser and Tracey Baute, OMAF / MRA) have set up pheromone traps for BMSB. We hope these will help provide early detection of BMSB. This week (June 16-18th, 2014), the BMSB IPM Working Group (US) met to discuss new information and research plans for 2014. Thresholds and management programs are still being developed in the mid-Atlantic US, where BMSB is abundant.

For those who are interested, most of the presentations for these meetings have been posted and can be found at www.northeastipm.org/index.cfm/working-groups/bmsb-working-group/bmsb-information/. Keep in mind that some of this information is still preliminary. Another website to check out is www.stopbmsb.org, and of course, we have general information on our OMAF / MRA website www.ontario.ca/stinkbug.

Most BMSB in Ontario have been found by homeowners, and in some locations, multiple reports indicate that local populations have been established. To date, BMSB has been confirmed in:

Golden Horseshoe and GTA: Hamilton (2010, established population), Burlington (2012), Milton (2012), Toronto (2012), Vaughan (2013), Niagara-on-the Lake (September 2013), St. Catharines (April 2014, photo only), Niagara Falls (winter 2014, photo only), Fort Erie (February 2014), Stoney Creek (February 2014)

Western Ontario: Cedar Springs (2013), Windsor (2013, 2014), Kincardine (2013), London (October 2013), Kincardine (November 2013), Paris (January 2014), Tecumseh, Maidstone (April / May 2014)

Eastern Ontario: Newboro (2012, established population), Ottawa (March 2014)

BMSB

Update

HORT MATTERS 6 June 20, 2014

In April 2014, NDSU extension published an excellent factsheet explaining what thermal inversions are, how to detect them and how they affect pesticide spray drift: http://tinyurl.com/NDSU-ae-1705. This article attempts to summarize the key points, but it is recommended that spray operators read the NDSU factsheet.

The Atmosphere The Earth is surrounded by a bubble of air called the atmosphere, and while you can’t see it, imagine it as a bubbling, swirling mass that moves like water. The lower part of the Earth’s atmosphere (the Surface Boundary Layer) is directly influenced by the Earth’s surface and everything on it (Figure 1). As it drags and percolates over the surface, it experiences relatively rapid changes in windspeed, temperature and humidity (on a time scale of an hour or less).

Atmospheric Temperature Dry air naturally cools with elevation, at a rate of about 1°C per 100 m. This change, called the Adiabatic Lapse Rate is caused by pressure changes with elevation. As we move up, the weight of the overhead atmosphere decreases, pressure drops, and air expands. That expansion takes work, and that creates the cooling effect (see red line, Figure 2). See how simple thermodynamics are?

When we add the effect of daytime solar heating and night time cooling, the rate of this temperature change is affected, and this changes how airborne particles like spray droplets settle, flow, and disperse.

Thermal inversions and spray drift

Dr. Jason S.T. Deveau, Application Technology Specialist

Dr. Tom Wolf, AgriMetrix Research & Training

Let’s consider a clear, relatively calm day:

Early morning On a clear, relatively calm morning, the sun emits short wave radiation, which is absorbed by the Earth’s surface. The surface conducts some of this energy deeper into the ground as well as heating the air near the surface. This creates a temperature gradient wherein the surface is warmest, and the air gets cooler with elevation (see red line, Figure 2).

As the air warms and expands, it becomes less dense and rises, similar to a lava lamp or hot air balloon (see Figure 3). As it rises, cooler air sinks and the air begins to circulate in a Convection Cell. This is called Thermal Turbulence, and is a very effective way for airborne particles, such as pesticide spray, to be rapidly diluted. This is also how the atmosphere disperses pollution.

If the morning were overcast instead of clear, the clouds would intercept much of the sun’s radiation, absorbing or reflecting it. As a result, the Earth’s surface would still warm up, but much more slowly. Thermal turbulence would be supressed.

Mid-late afternoon As the sun passes over and the wind starts to rise, the convection cells get disrupted by the wind and experience mechanical turbulence (see blue line, Figure 2). This type of turbulence mixes warmer air near the ground with cooler air above it, and also suppresses thermal turbulence.

Figure 1 – The Earth’s Atmosphere. The illustra-

tion of the Earth is to scale, but the landscape is

not. Our focus in on the Surface Boundary Layer.

Figure 2 – Three

possible atmospheric

temperature profiles in the

Lower Troposphere.

HORT MATTERS 7 June 20, 2014

Mid-afternoon to night As the energy from the sun lessens, the soil begins to cool, which in turn cools the air next to it. Once the air cools enough to be colder than the air above it, we have the beginning of a Temperature Inversion (see green line, Figure 1). It is called that because it is now the reverse of the typical day-time temperature profile. The height of the inversion grows with time, reaching a maximum of about 100 m by sunrise. Within the inversion layer, thermal turbulence no longer ex-ists.

How Inversions affect Dispersion We now know that during a sunny day, solar energy warms the Earth’s surface, and the air near the surface, more than air above it (see red line, Figure 2). We also know that this causes convection cells to circulate (Figure 3). The rising parcel of air will cool and shrink as it rises through the relatively cooler air above it. Conversely, cool parcels of air fall feely through warm air, and the resulting mixing action allows airborne particles (such as pollution or pesticide spray) to become much less potent at ground level. This protects us from drift damage (see Figure 4).

Now let’s imagine an air parcel that is displaced upward during an inver-sion. This time it is cooler than the air above it, and as it begins to rise it gets denser. This prevents it from rising, and it will return to the layer where started. In other words, it stays where it is. It is the same for a sinking par-cel of air: it will start off warmer (and less dense) than the air below it, but will warm further as it falls. As a result, it will want to rise back to its origin.

The result is that in an inversion, air does not mix by thermal turbulence. Spray drift (or vapour) stays concentrated in the cold air into which it was released. And cold, dense air tends to move downhill or laterally with light winds, taking any spray drift particles with it.

Figure 3 – A hot-air balloon is a metaphor for con-

vection cells that create thermal turbulence.

Figure 4 – Thermal Turbulence allows particle-laden warm air to rise and clean cool air to fall. This disperses

air-borne particles like pollution or pesticide.

How Clouds and Wind affect Inversions As mentioned earlier, clouds absorb energy from the sun as well as the long-wave radiation from the Earth’s surface. They also reflect radiation from the Earth back to the soil. This is why overcast nights are warmer than clear ones. Inversions are not affected by light wind (e.g. 6 to 8 km/h), but as the wind increases and mechanical turbulence mixes the air, the strength of the inversion will be reduced and the atmosphere will approach a neutral condition (see blue line, Figure 2). There may not be an inversion, but spraying would still be inadvisable if the wind got too high.

Therefore, extended periods of mostly clear skies in the evening or night when the wind is light means a high probability of strong temperature inversions. Conversely, cloud cover usually means a near neutral atmosphere, so no strong inver-sion.

Humidity affects Inversions Inversions form more rapidly when there is less water vapour in the air to absorb radiation. Once humid air has cooled to the dew point, water condensation gives off energy and warms the air a little. This slows the formation of the inversion. Be aware that inversion conditions can exist long before fog forms, so fog is not a good indicator for the beginning of an inversion – you’re already in one.

Soil Conditions and Shade affect Inversions This is a complex issue, but soil conditions that make inversions more intense include low soil moisture, freshly tilled soils, coarse soils, heavy residue and closed crop canopies. Further, inversions in shaded areas (e.g., behind wind-breaks) start sooner, and last longer. See the NDSU factsheet for more detail.

HORT MATTERS 8 June 20, 2014

Figure 5 – Thermal Turbulence is supressed during a Temperature Inversion. Particle-laden cool air at

the surface cannot rise, and warm, clean air cannot fall. No dispersion occurs, and the concentrated,

particle-laded air tends to move downhill or laterally with light winds.

Inversions and Spray Drift When you spray during an inversion, the larger drops fall quickly, but smaller lighter droplets fall very slowly (a few centimetres per second). The do not disperse (as in Figure 4). Instead, they float along with the cool air, evaporating very slowly, over great distances (see Figure 5). These small particles, as well as vapours from volatilizing products, are capable of moving for kilometers.

Spray Timing Inversions, once formed, persist until the sun rises and warms the Earth’s surface, or until winds increase and mix the stationary layers of air together. Therefore, spraying in the evening poses the greatest risk for pesticide drift when condi-tions favour inversions. Very early mornings (e.g. around sunrise) are not much better. Remember, at sunrise, the inver-sion will be at its maximum height.

The rising sun will warm the earth and create turbulent conditions near its surface (e.g. a few metres). It takes a few hours of sun for the inversion to burn off to a sufficient height to adequately disperse once again. Most inversions will have dissipated two hours after sunrise, which may be the best choice for spraying.

Detecting an inversion The only sure way to know if you are in an inversion is to take two temperature readings: the first about 10 cm from the ground, and the second about three metres off the ground. If the surface temperature is cooler, you are in an inversion. The magnitude of the difference indicates how strong the inversion is. Accurate measurements are difficult to manage with conventional thermometers, so it is generally easier for sprayer operators to watch for the following cues:

Large temperature swings between daytime and the previous night.

Calm (e.g. less than 3 km/h wind) and clear conditions,

Intense high pressure systems and low humidity where you intend to spray

Dew or frost (fog may be too late)

Smoke or dust hanging in the air or moving laterally,

Odours traveling large distances and seeming more intense,

Daytime cumulus clouds collapse toward the evening

Overnight cloud cover is 25% or less

If you suspect a strong inversion, don’t spray. Stop drift before it starts.

Turfgrass: The temperature is ramping up in the daytime, but thankfully, the night time temperatures are going to remain

below 20C. This is good news for the hot weather foliar diseases such as Pythium blight and brown patch which need those

higher night temperatures to develop and cause extensive turf damage. The hot days and cool nights are perfect for heavy

dew formation and dollar spot development. If you don’t have your preventative fungicide application for dollar spot down, it

is probably a good time to do that. What you may see with the high humidity that accompanies overnight thunder storms is

white mycelium associated with dollar spot which can easily be mistaken for Pythium blight. The spring growth flush has

occurred and the turf probably needs a pick me up. This is especially true for turf that is irrigated and will continue to grow

throughout the summer such as golf course turf and irrigated sports fields. Home lawns do nicely with a slow release fertiliz-

er or an organic source of N that will be released slowly over the summer. On home lawns, fertilizing now will also help the

turf fill the voids after an application of the broadleaf herbicide Fiesta and help the turf recover from seedhead production.

An application at this time of 0.3- 0.5kg/N per 100m2 is the right amount for this time of year, especially on mature stands

of turf. On golf course turf, N at this time of the season will help protect against heavy dollar spot infection. Fertilizing at this

time of year is tricky though. You want to have enough N to help minimize dollar spot and anthracnose but not so much that

you encourage the warm temperature foliar diseases such as brown patch and Pythium blight. Young seedlings that are just

getting established this spring after winter injury will particularly susceptible to these foliar diseases that attack seedlings.

HORT SHORTS - June 17

HORT MATTERS 9 June 20, 2014

HORT MATTERS 10 June 20, 2014

Agricultural Information Contact Centre: 1-877-424-1300

E-mail: ag.info.omafra@ontario.ca

www.ontario.ca/omafra Queen’s Printer for Ontario, 2013

Use of Sandea herbicide in tomatoes, vine crops,

sweet corn and peppers Darren Robinson, Weed Researcher, Ridgetown Campus – University of Guelph

Sandea and Permit are Group 2 herbicides that are taken up by roots and shoots and are systemic in the plant. The herbicides will translocate to the new growing tissues, and if applied to a sensitive crop or weed, it will cause stunting, chlorosis (yellowing) and may even delay maturity of sensitive species. These herbicides are particularly useful for control of preemergence control of common lamb’s-quarters and postemergence control of yellow nutsedge. They have also provided good control of common ragweed and redroot pigweed. The labels should be consulted before use in all cases, and are available at: www.uap.ca/products/documents/Sandea31209_E_Approved_25MAR2014_Label.pdf www.uap.ca/products/documents/PermitElabel-140325-apprvdwlogo.pdf

Tomatoes: Sandea is particularly useful for control of common lamb’s-quarters when applied prior to transplanting and before emergence of the weed. Its efficacy on common lamb’s-quarters is significantly reduced when applied postemergence. Though it can be applied postemergence to tomatoes, temporary injury (ie. chlorosis) is possible when applied in hot, humid weather.

Vine Crops: Sandea can be applied both preemergence and postemergence, though growers are cautioned to con-sult the label for product rates, as they vary depending on crop species and application timing. Best results have been obtained when Sandea is applied in a tank mix with Command, prior to crop emergence, followed by a postemergence application of Sandea alone later in season.

Sweet Corn: Permit can be applied postemergence in sweet corn, and is particularly useful for control of yellow nutsedge. Growers should consult the label for information on rates, variety sensitivity, and corn leaf stage.

Peppers: Care should be taken when applying Sandea to peppers. The label indicates that Sandea should be ap-plied as a directed-postemergence application between pepper rows. Injury may be possible with certain pepper varieties.

Nursery and Ornamentals con’t: The cool, weather this spring slowed down leaf emergence and allowed for the successful

infection of several plant pathogens on woody ornamentals. High levels of anthracnose, leaf spots and and other leaf dis-

eases are in many areas. Oak leaf blister (Taphrina caerulescens) is not usually an issue but this year it is rampant in the

landscape. Although it looks unsightly, it does not significantly impact tree health, it’s too late to do anything about it now.

There is still A LOT of dieback in the landscape and many horticulturalists are predicting that it’s not over yet. Winter injury

(e.g. freeze\thaw or low temperature injury) causes damage to the conductive tissue under the bark. During cool, wet

springs like this one, damaged trees and shrubs may still be able to send enough water up to expanding foliage and twigs

to keep them going for a while. But once it becomes hot and dry, those compromised branches and twigs will not have

enough live conductive tissue to support the canopy and branches will “suddenly fail”. I’ve seen this happen as late as mid

-July. If you see branches crashing over the next few weeks, chances are it’s not Verticillium wilt….it could very well be win-

ter injury. When in doubt, slice through the inner wood of the branch and look for greenish-black discolouration of inner

vascular tissue as a sign of Verticillium. Powdery mildew is common on deciduous flowering shrubs and herbaceous peren-

nials. Adult bronze birch borer beetles are actively laying eggs on the bark of susceptible birch (e.g. Betula pendula). Symp-

toms of larval boring damage appear as branch tip death, branch death and death of the leader and progresses quite

quickly. ADULT Potato leafhoppers are feeding and laying eggs on the newest leaves of maple (Acer platanoides, A. sac-

charum). Our nursery scout found them on Acer platanoides, Acer rubrum last week and we have already seen dam-

age. Susceptible crops are those that are flushing new leaves (leafhopper’s favourite food source). Aphids are quite numer-

ous on herbaceous and woody ornamentals, and they also attract ants. Gypsy moth larvae (3rd and later instars) are moving

into their heaviest feeding period in the next couple of weeks. We have been finding GM larvae feeding on Colorado spruce

as well as deciduous trees and other evergreens. Oystershell scale crawlers have hatched. Maple spider mite

(Olygonychus aceri) can be found feeding on the undersides of leaves of red and red x silver maple hybrids. The first gener-

ation of Euonymus scale crawlers have hatched in container production. Larvae of European pine sawfly are feeding in

clusters on last year’s (and older) needles. Taxus or Fletcher Scale nymphs are still developing on foliage and twigs of Tax-

us and Thuja. Taxus mealybug nymphs will be showing up. Cedar leaf miner larvae are pupating and tiny, grey-white adult

moths are emerging.

HORT SHORTS - June 17