Getting Into the Weeds - November 19th, 2019

Thursday, November 14, 2019

This winter, Perennia Horticulture Specialists Rosalie Gillis-Madden and Jennifer Haverstock, are planning a workshop series called "Getting Into the Weeds."  This series will offer an in-depth look into certain aspects of horticulture production.

In collaboration with NSDA Regional Offices, the inaugural session is taking place on Tuesday, November 19th, from 10:00 - 11:30 at locations across the province.  Topics for discussion include: High Tunnels – site selection and preparation, and long term nutrient management, as well as soil-less substrate and different potting technologies. Using remote technology, we are excited to welcome guest speakers from across North America.

  • Elizabeth Buck, Extension Vegetable Specialist, Cornell Cooperative Extension Vegetable Program Avoiding a “Tunn”-el of Trouble: Site Selection and Prep
  • Judson Reid, Extension Vegetable Specialist, Cornell Cooperative Extension Vegetable Program High tunnel soils: Long term nutrient management for crop health
  • Shawn Mallen, Sales and Hydroponics Manager at A.M.A., Horticulture Inc. Substrate and Potting Choices in Tunnel Production
Admission is free, but space is limited, so we ask that you register in advance.  The deadline to register is Nov 18th at noon.  For details on how to register and to find the location nearest you, please click here!

Garlic spacing

Friday, September 27, 2019

John Zandstra from Ridgetown College in Ontario did some research on garlic spacing back in 2000, using the cultivar 'Music.'  A spacing of 10 cm between cloves and 65 cm between rows was standard practice in Ontario at the time.  They tried several spacings in a couple of different trials:
  1. 65 cm (25.5") between rows, 
    1. Cloves spaced at 5 cm (2")
    2. Cloves spaced at 10 cm (3.9")
    3. Cloves spaced at 15 cm (5.9")
  2. Cloves spaced 10 cm (3.9") apart
    1. Rows spaced at 65 cm (25.5")
    2. Rows spaced at 45 cm (17.7")
    3. Rows spaced at 25 cm (9.8")
    4. Rows spaced at 15 cm (5.9")
In the first trial, they found that decreasing the clove spacing from 10 cm to 5 cm resulted in a decrease in bulb weights by 15%, however yields increased by 74%.  For growers looking to increase their seed garlic quickly, but have limited acreage, a closer clove spacing may make sense.  Increasing row spacing from 10 cm to 15 cm did not affect bulb size, but decreased yields by 32%.  

In the second trial, significant increases in yield were found as garlic row widths narrowed, and bulb weights only dropped a little bit. Depending on the flexibility of your market and their willingness to accept slightly smaller bulbs, narrowing row spacing can have dramatic affects on yield.  To read the full report on the spacing trial, please click here.

Zandstra 2000: 10 cm between cloves with variable row widths, cultivar 'Music"

WANTED: Your post-harvest garlic losses.  I am working on a garlic storage disease factsheet, but I need your punky garlic for a photo op.  Growers who are registered farms in Nova Scotia: please bring samples to either Perennia (32 Main Street, Kentville, NS or 199 Dr Bernie MacDonald Drive, Bible Hill, NS) or to your Nova Scotia Department of Agriculture Regional office.  It is recommended that samples are brought in on Monday, Tuesday or Wednesday so they are not sitting on a truck or in an office over the weekend.

Lingering effects of Hurricane Dorian

Thursday, September 12, 2019

The Nova Scotia Federation of Agriculture recently sent an alert directing growers who continue to be in emergency situations impacting animal welfare, crop storage, etc.  (no power, generator failures, challenges accessing fuel for generators, access to reefer trucks, etc.) to contact Nova Scotia’s Emergency Management Office.  For more details, please see the full NSFA statement here.  

Late-season foliage loss in winter squash

Wednesday, September 11, 2019

Hurricane Dorian caused widespread damage in Nova Scotia.  Many cucurbit plants lost significant amounts of foliage.  Late-season foliage loss in winter squash and pumpkin leave the fruit exposed to sunscald.  If your crop has lost enough foliage so that there is no longer sufficient canopy protection to prevent sunscald, it is recommended that you harvest your squash and pumpkins.

Fig. 1. Sunscald on butternut squash, three
weeks post-storm.
Sunscald injury (Figure 1) occurs when cucurbit fruit are exposed to direct sunlight during the later stages of fruit ripening - while this year this is predominantly due to Hurricane Dorian, this can also occur as a result of powdery mildew, bacterial wilt, Phytophthora blight, or other pests.  Sunscald injury will result in rind tissue collapsing in the exposed area.  Initially the rind may appear water-soaked - on pumpkins this can be hard to observe at first and the area might just appear slightly sunken.  Darker skinned squash (particularly green acorn) will show sunburn fairly quickly.  Affected tissues can look bleached (Figure 2) and the rind may slough off when rubbed.  Over time, the fruit tissue may become tan, brown, or black (Figure 3), a result of secondary pathogens invading, and will eventually collapse.

Fig. 2. Sunscald on Sweet Mama, three weeks post-storm.
Typically, it is recommended that pumpkins and winter squash are harvested when they are fully mature for optimum quality and storability.  Fully mature pumpkins and winter squash will typically have a more hardened skin that is resistant to puncture with a thumbnail.  Fully mature
fruits will often have lost rind surface gloss and may have ground-spot yellowing.  Mature fruit that are left attached to vines are prone to infection in the stems and fruit.  As long as pumpkins have started to turn colour, they will continue to ripen off the vine if held under proper conditions.  When harvesting, avoid bruising the fruit or damaging the skin as this will result in storage rots setting in.

Proper curing and storing will greatly enhance the storability of your crop.  Note that chilling injury will occur if stored below 10°C (50°F).

Fig. 3. Sunscald on Sweet Mama with secondary infection,
three weeks post-storm.
The best conditions for ripening pumpkins are in a well-ventilated area at 27- 30°C (80-85°F) with relative humidity of 80-85%.  The curing period should be about 10 days.  This will help the fruit to ripen, the skin to harden, and any wounds to heal.  After curing, pumpkins should be stored in a cool, dry place (10 - 15°C or 50 - 60°F) with a relative humidity of 50-70%.

The best conditions for ripening squash are in a well-ventilated area at 21- 27°C (70-80°F).  How long squash will typically keep under optimal storage conditions depends on squash type.  Cornell has a chart outlining optimal storage temperatures and relative humidity based on squash type, which can be found here.  Note that if Acorn squash is stored below 13°C, it will become stringy.

The goal is to maintain enough humidity so that the fruit doesn't desiccate but not so much that condensation occurs which can promote bacterial and fungal growth.  Storing at higher temperatures results in weight loss, and at lower temperatures chilling injury can occur.  All fruit that is placed in storage should be free from disease and in good condition to promote the longevity of the crop's storage life.  Pressure bruises from packing fruit too tightly or too high can also result in reduce marketability of your squash and pumpkins.

Onion smut

Tuesday, August 20, 2019

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.

Hailstorms and crop impact

Tuesday, August 13, 2019

The hail storm over the weekend caused scattered damage in the Annapolis Valley, as well as in Hants, Colchester, and Cumberland Counties.  The degree of damage depends a lot on location and crop type, as well as on wind velocity, the size and shape of the hailstones, and how long the hail lasted.  The warm, wet weather that followed the storm can exacerbate disease problems, especially bacterial infections.

Fig. 1. Healing hail damage on butternut squash,
two weeks post-storm.
Crops with large leaves such as Cucurbits will typically look pretty destroyed, but, depending on the severity of the damage to the leaves, and how well the fruit were protected, might pull out of it with minimal yield loss.  If the Cucurbits are on a drip system, a little extra nitrogen will encourage the regeneration of leafy growth.  Damaged zucchinis and summer squash should be removed.  Leaving damaged fruits on the plant, which are unlikely to be marketable, will be a drain on the plant's resources and could result in more prolonged yield losses.  Depending on the severity of damage, many winter squash will scar-over (Figure 1, Figure 2).  Healed scars should not pose a disease risk, but may render the fruit undesirable to some buyers.
Fig 2. Healed hail damage on butternut squash,
seven weeks post-storm.
Other crops that are susceptible to bacterial rots (Figure 3) such as onions will have long-lasting damage - crop injury (Figure 4) opens the door for bacterial infection, which quickly spreads down the leaves into the bulbs.  Dead tissue is prime for stemphylium infection.  Growers are encouraged to continue with preventative stemphylium sprays.  Copper may help with bacterial infection, but results have been poor on onions in the past.

Leaf loss in crops close to harvest such as sweet corn or root crops should have minimal effects on yield.  However, direct impact on sweet corn ears can render them unmarketable, depending on the degree of damage.

Fruiting vegetables such as peppers will be more prone to sunburn if protective foliage has been badly damaged.  Fruits that have taken a direct hit, depending on the size of the hail stone and the velocity of the strike, can be unmarketable.

Fig. 3. Bacterial infection spreading down an
onion leaf
Losses of flowers and small fruit will reduce yield and delay harvest in crops such as green beans.

Wounds in plant tissue open the door for diseases to come in.  It is recommended that a protectant such as copper or Bravo be applied (if labeled) for your damaged crop, which will help guard against infection while the plant heals.  Always read and follow the label, the most up to date labels can be found on the Health Canada website.

If you have Crop Insurance, it is recommended that you reach out so that they can document the damage.  Should a claim be necessary down the road, they will have a record of how extensive the damage was, which will make filing a claim easier.  The days just after a hail storm are often the worse.  Apply a protectant, maybe give your crop a bit of extra fertility, if appropriate, and then come back in a week to see how things look.  If the crop pulls out of the damage, then no insurance claim needs to be filed.  Registered farms in Nova Scotia shouldn't hesitate to contact Perennia if you are unsure of best management practices in crops that have been affected by adverse weather.
Fig 4. Hail damage on onions

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Garlic harvest!

Friday, August 2, 2019

Wrapper leaves snug around cloves.
Garlic harvest is upon us, and if you haven't already started harvesting your garlic, now would be the time to start planning it.  Different varieties will mature at different times, so it's always good to check on bulb development of few bulbs of each variety.  One way to determine harvest-readiness is by looking at the number of green leaves.  Each leaf corresponds to a wrapper leaf around the bulbs.  Wrapper leaves protect the cloves from light, moisture, heat, etc.  For best storability, it is suggested to harvest with five to six green leaves.  That way, if a wrapper leaf or three is lost in harvesting and cleaning, there will still be two to three wrapper leaves around the bulb to protect it from storage rots, desiccation, etc.

Stem and bulb nematode damage
Green leaves should be used as a guideline, but not a rule.  Sometimes on a particularly healthy plant, the leaves can remain green despite harvest-readiness.  Alternatively, if there is heavy thrip damage, high stem and bulb nematode populations, etc. the leaves can brown prematurely.  It is always best to pull a few bulbs and check to see how the cloves are filling the wrapper leaves.  Give the bulb a squeeze, and if there is any give, then the garlic isn't quite ready yet.  You should also cut the bulbs in half perpendicularly to the stem.  Each clove should be tight in the wrapper leaves.  If the wrapper leaves seem a little loose around the cloves, then wait a little longer to harvest.  The cloves in harvest-ready garlic will also start to pull slightly away from the stem, especially in hardneck varieties. 

Cloves starting to pull away from stem.
Hardneck varieties (Allium sativum var. ophioscorodon) produce scapes.  Hardneck types, as a general rule of thumb, produce larger cloves, but have a shorter storage life, which can be greatly influenced by harvest timing.  If you leave harvest for too long, the wrapper leaves will start to decay, and the cloves will continue to grow and pull away from the stem and the bulb will split open, rendering the bulb unmarketable.  Softneck varieties (A. sativum var. sativum) do not produce a scape, and typically have a longer storage life.

Garlic harvested too early might not have fully developed its yield potential or flavour profile, and will tend to shrivel when cured.  Late-harvested garlic is more likely to have poor storability, particularly the hardneck varieties, as the wrapper leaves start to deteriorate, exposing cloves.  It is often better to harvest a little early than a little late.

Target harvest for early in the morning on a dry day for best results.  Do not leave garlic in the sun for long as it can scald, and the cloves will quickly deteriorate.  Handle garlic gently as it is sensitive to bruising.  The higher the moisture or relative humidity when you are drying your garlic, the slower the garlic will dry down and cure, resulting in high disease potential.

Post-harvest handling can dramatically affect garlic quality and storability.  Recent research from Cornell University suggests that root trimming does not have any impact on bulb quality, weight, or disease incidence.  Washing garlic post-harvest, while resulting in good looking bulbs initially, ultimately resulted in more discolouration after drying and curing.  For more details about post-harvest handling of garlic, check out Cornell's Garlic Post-Harvest Study.