Nova Scotia Garlic Industry Survey!

As garlic planting season is upon us, it seemed timely to roll out our garlic survey!  Garlic is widely grown across Nova Scotia.  We are hoping to put together some programming around garlic production in the coming months and wanted to assess the state of the garlic industry so that we can better serve you!  The goal of this survey is to determine where outreach and support might help the industry move forward.  This survey should take about 15 minutes to complete. 

The mission of Perennia is to help farmers, fishers, and food processors be prosperous and profitable.   

Garlic harvesting time

Hard neck garlic harvest in Nova Scotia typically happens the first week of August, although with how hot this summer has been (Table 1), some varieties are a bit ahead of schedule.

Table 1. Degree day accumulations as of July 26, 2021.  All data are taken from the Kentville weather station, based on a start date of March 1, and calculated using the single sine method.

 

Fig. 1. This garlic from mid-July, isn't quite ready to
harvest. Note how the wrapper leaves aren't yet snug
around the cloves.

I have blogged about garlic harvest timing in the past, and if you haven't come across it before, I strongly recommend giving it a read!  The number of green leaves left is a good tell, but if your garlic is super healthy, or super sick, it might not be the best barometer (Fig. 1).  You can find the blog post by typing "garlic" into the search bar on the right of the NS Vegetable Blog, or for direct access, click here.  

By mid-August my car usually smells of garlic from all the samples of unhappy garlic I've collected from growers.  This is often the result of poor post-harvest management.  August in Nova Scotia, when growers are trying to cure their garlic, is often a muggy month, providing poor drying conditions. 

Fig. 2. Relative humidity and temperature.

You NEED good air circulation and ideally low relative humidity (less than 70%) in your curing space otherwise you run the risk of disease running rampant.  If your garlic is taking more than three weeks to cure, it is likely your relative humidity is too high.  There are cheap sensors available from Canadian Tire or Amazon to measure relative humidity and temperature.  If you are serious about growing garlic, I strongly recommend you get one.  Some of the nicer sensors even upload it to a web portal (Fig. 2) so you can check on it from the comfort of the couch. Move the sensor around your drying space to see if you can find any "dead" space with low air movement and higher relative humidity.  Those are the areas where disease is most likely to rear its ugly head.  It is best to try and move some fans to around to get rid of this dead space.

Fig. 3. Unhappy garlic - Penicillium (blue) and
Rhizopus stolonifer (white and black fungus). 

Did you know you could submit samples to 
Perennia's Plant Health Lab?  This service
is often free for registered farms.  Reach out to
me, Rosalie Gillis-Madden, if you have a vegetable
sample you want to submit to the Plant Health Lab.

It shouldn't need to be said that diseased garlic should not be used for seed.  Advanced growers with smaller plantings sometimes earmark particularly healthy plants in the field before harvest as candidates for seed stock.    To read more about garlic storage, post-harvest diseases, and planting stock considerations, check out Perennia's factsheet.

Fig. 4. Garlic storage, post-harvest
diseases, and planting stock considerations
fact sheet.

Garlic Harvest

As we move toward garlic harvest season, there are some important factors to keep in mind that will help determine the best time to harvest. 

Harvest timing is very important in preventing post-harvest diseases. Garlic should be harvested with five to six green leaves and before the cloves start to pull away from the stem. Green leaves correspond to the wrapper leaves around the cloves which protect them from light, moisture, and heat during storage. As the wrapper leaves start to deteriorate, the cloves will continue to grow and pull away from the stem causing the bulb to split open. Besides being unmarketable in this condition, exposed cloves make for poor storability. 

Check out Perennia’s new “Garlic Storage, Post-Harvest Diseases, and Planting Stock Considerations” factsheet for more information.

Garlic spacing

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.

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Garlic harvest!

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.

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Garlic scape removal

If you haven’t signed up for it before, OMAFRA has a fantastic vegetable blog.  A couple of years ago, Travis Cranmer, OMAFRA’s Allium Specialist, wrote a great piece about the benefits of removing garlic scapes.

Figure 1. Yield and bulb weight in response to scape removal timing of
garlic cv. ‘Music’. (Zandstra, 2006)

John Zandstra did some research on scape removal and the influences it has on yield.  Scapes should be removed sooner rather than later to preserve yield and bulb size (Figure 1). The longer you leave the scapes growing in the field, the more energy the plant will divert to creating a flower and bulbils - to the detriment of bulb size and yield.

Figure 2. Influence of leaf removal on yields and bulb weights of
garlic cv ‘Music’. (Zandstra, 2000)

Best practices also suggest that the scapes should be removed by hand (Figure 2).  Using a sickle bar mower, or other mechanical means to remove the scape often damages leaves.  Damage to the leaves reduces the photosynthetic potential of the plant, resulting in less energy to be poured into bulb development.  In short, even a small percentage of leaf damage will reduce bulb weight and total yield so be careful when removing scapes!

Scape removal is also a good time to be on the lookout for leek moth damage in your crop. Leek moth is a new pest to Nova Scotia and has been found in Kings and Annapolis Counties.  Cornell has an excellent site devoted to providing further leek moth information.  If you grow garlic, leeks, or onions, I strongly suggest you make yourself familiar with this pest.

Leek moth damage on garlic, photo credit Amy Ivy, Cornell

Leek moth damage on garlic leaves, photo Amy Ivy, Cornell

Leek moth damage on garlic scapes, photo Scott Lewins, UVM

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).

Time to Harvest Garlic

It is time to harvest garlic now.  It is important that garlic be properly dried and cured. A good post was written on this topic last year.  If you click on postharvest under categories on the lower right side of the blog page you will see last years post.

Garlic Scapes

Garlic scapes are the immature flower stems of garlic (Allium sativum).  They begin to develop in midsummer.  If your main crop is garlic bulbs, remove the scapes when they begin to curl so that the plant focuses most of its energy into bulb production.  If the scapes are not removed total yield may be reduced by 5-25 percent depending on several factors such as soil fertility.

To harvest garlic scapes, carefully pinch or cut them off just above the top leaf.  Instead of discarding the scapes, market them for use in a wide variety of foods.  Garlic scapes have a mild, gentle garlic flavor and can be added to many dishes or used as a side dish. 

 

Garlic harvest and postharvest

Garlic growers are harvesting their crop these days.  In general garlic may be harvested when the leaf tops begin to discolor and dry.  If the bulbs are immature when harvested they will tend to shrivel when cured.  If harvested too late, the bulbs may be discolored and the outer papery covering will break down exposing the individual cloves.  Garlic is ready for harvest when the cloves are fully segmented but the bulb is still tightly encased by an intact outer skin.

Given wet weather and increased humidity, curing and postharvest storage are critical in the production of quality garlic.  Garlic must be cured for several weeks prior to storage.  Under very humid conditions, the bulbs can also be cured on racks in forced air dryers at low temperature and low humidity.  The bulbs must be thoroughly dried before placing in long term storage.  Mold growth can be a problem if garlic is not cured properly before storage.
 

 

When properly cured, garlic keeps well under a wide range of temperatures.  Store cured garlic in open-mesh sacks in a dry, well-ventilated storage room.  

 

 

 

Garlic and Onion Diseases

I wrote about white rot and its risk to garlic industry in Nova Scotia. That threat is still real and growers should be using only seed from clean seed program.

Aside from white rot, there are other garlic diseases which can be devastating to garlic crop, namely botrytis and downy mildew. I have already seen some heavy botrytis disease pressure in commercial garlic crop plantings. Warm and humid weather is very conducive for disease development.

Botrytis and downy mildew are serious crops of onions and growers must apply fungicides to keep those diseases to the minimum.

For registered fungicides in garlic please visit: 
http://www.agrapoint.ca/Pest%20Management%20Guides/Vegetables/2012/Garlic%202012.pdf

For registered fungicides in onion crop please visit:
http://www.agrapoint.ca/Pest%20Management%20Guides/Vegetables/2012/Onion%202012.pdf

Garlic - Watch for White Rot

The garlic crop in general overwintered well and scapes are emerging these days. As you all know, those needs to be removed before they unwind. This is also a time to monitor for diseases. The most devastating disease of the onion family is White Rot and it was unfortunately found in Nova Scotia in the past growing season.

Leaves of plants infected with the White Rot pathogen show yellowing, leaf dieback, and wilting. Leaf decay begins at the base, with older leaves being the first to collapse. 

Roots also rot, and the plant can be easily pulled from the ground. Associated with the rot is a fluffy white growth which develops around the base of the bulb.

As the disease progresses, the mycelium becomes more compacted with numerous small black bodies. These sclerotia, the resting bodies of White Rot, are approximately the size of poppy seed and may persist in soil for over 20 years.

Healthy Garlic Crop

Garlic with signs of White Rot infection

If you are interested in a CD copy of the talks on Diseases by Rick Delbridge from the Garlic Workshop held in March 2012, please call Gail at (902) 678-7722.  We will ten copies at the office by Monday and then hope to have them available on line shortly thereafter.