Hailstorms and crop impact

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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New pesticide registrations

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

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

Freezing Injury Observed on Tomato, Pepper, Eggplant and all Cucurbits

Frost  that occurred on May 26 and May 28 caused widespread damage on crops which were not protected with covers.

Although frost occurs, by definition, when the temperature drops to 0° C at 1.5 meters above the ground, this may or may not result in freeze damage to crops. The actual temperature at which freezing will occur depends on such factors as plant species and variety, plant vigor, soil conditions, surface cover, duration of the freezing temperature, thawing conditions, cloud cover, and wind conditions.

In tomato, freezing causes a darkening of the leaf or stem tissues as seen on the picture below. Damaged areas later wilt and turn brown. It may be difficult, initially, to determine whether the growing point has been killed and damage may become more evident on the day after the frost. 

Peppers (below) and eggplants are more sensitive than tomatoes to freezing temperatures and may be injured or killed by a light frost. 

Cucurbits are also very susceptible to light frost injury. While it is possible to replant some short seasoned crops such  zucchini and cucumbers, it is getting late for replanting peppers, eggplants and tomatoes.

Insect and Floating Row Covers

Insect covers provide an alternative pest control option for growers.  Insect covers come in different sizes and are suitable for control of a whole host of insects such as carrot rust fly, cabbage maggot, and flea beetles.   Insect covers will create a physical barrier between the crop and flying insects.  It has to be applied tightly so insects are unable to get under the netting.

 

Insect cover on rutabaga

 

Insect covers do not trap heat and therefore are used on cole crops, carrots etc where extra heat might be undesirable.  On the other hand crops such as cucurbits, lettuce and peppers may benefit from extra heat, so floating row covers are more beneficial.

 

Floating row cover on lettuce