Soil salinity in Nova Scotia high tunnels

When evaporation from the soil surface and transpiration from plants exceeds water input, salts can start to accumulate at the soil surface. This is because when water from the soil surface evaporates, it wicks salts that are suspended in the soil solution to  the soil surface.  This is particularly a problem in high-tunnels that are in production year-round.  

Accumulating salts are not just sodium (Na⁺) and chloride (Cl^-) ions, but are also essential plant nutrients... calcium (Ca²⁺), magnesium (Mg²⁺), potassium (K⁺), ammonium (NH₄⁺), hydrogen (H⁺), phosphate (HPO₄^2-), sulfate (SO₄^2-), and nitrate (NO₃^-) are all salts. Nitrate accumulation is particularly frequent in high tunnels as high-value crops are well fertilized, and since there is no rainfall to leach the nutrients, they accumulate year after year.

To learn more about soil salinity, how it happens, and what you can do about it, please read Perennia’s factsheet: http://www.perennia.ca/wp-content/uploads/2015/12/Soil-Salinity-NS-Hi-Tunnels.pdf 

Late Blight of Tomato

The recent weather has been conducive to the development of late blight of tomatoes.  Producers should be vigilant in keeping up with their spray program.  The 2014 Tomato Management Schedule contains up-to-date information on registered products.

For more information on the symptoms of late blight on tomato select blight from the category menu on the lower right side of the blog page, one of the three posts that show up is called 'Late blight of Tomatoes.'

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.

Late Blight of Tomatoes

The weather conditions this year have been favorable for early and late blight on tomatoes.  Given the right conditions and an early initial infection, late blight can be a devastating disease on both tomato and potato crops. 

 

The most common symptoms on tomatoes are sunken, dark green or brown lesions on leaves and brown lesions on stems, with white fungal growth developing under moist conditions.  

 

 

 

Preventative measures include sound crop rotation, proper spacing, pruning, and avoiding overhead irrigation.  The key is spraying preventatively.  Once plants are infected with late blight, it's too late to save them.  Before using any products, read the label and then use accordingly.  For more information please refer to Perennia’s Tomato Management Schedule, a guide to weed, insect and disease management in tomatoes.

Watch for Tomato Diseases

Tomato Leaf Mold

 
Due to a wet growing season the tomato crop, especially in high tunnels, has been infected by leaf mold. Some growers experienced difficulties associated with leaf mold in June while others are getting their crop infected now.

Tomato leaf mold is caused by Fulvia fulva (also known as Cladosporium fulvum).  This fungus attacks during cloudy, humid weather and can be particularly severe in plastic greenhouses.  We certainly have had weather that would favour this pathogen.

 
Tomato leaf mold can spread very quickly under humid conditions such as we have been experiencing lately.  It is key (even more important than fungicides) to increase air flow through the crop and to lower the humidity.  It is advisable to crack the vents at dusk and increase night-time temperatures so that they are above outdoor temperatures to prevent high humidity in the greenhouse. 

Heat during rainy days might also be required.  Pruning off the lower leaves will help to get air flow through the crop and reduce infection.  Air movement with fans is also a good idea.  If the infection is serious and the crop is nearing the end of production, it might be best to harvest what you can without investing more money/effort in control. 

There are not many fungicide choices.  Fontelis and Pristine are registered for Cladosporium suppression on other crops, but both fungicides are also registered on tomato for Botrytis and Alternaria control.

Early blight, botrytis and septoria have all been found in tomato crops.  Given warm, humid weather it is likely that before too long we might see late blight on tomatoes.  In addition to proper canopy management, pruning out the diseased foliage and proper ventilation, it may be necessary to keep ahead of diseases by providing periodic fungicide applications.  For more information please see the Tomato Management Schedule - a guide to weed, insect and disease management in tomatoes.

Tomato Pith Necrosis

Tomato pith necrosis, a newly emerging disease of tomatoes, is caused by Pseudomonas corrugata and appears to develop when there are low night temperatures, high nitrogen levels and high humidity.  The bacteria may be seed-borne but the epidemiology is poorly understood.  

Tomato pith necrosis has been found in the Nova Scotia greenhouse tomato crop this season.

Early symptoms of this disease include wilting of foliage and chlorosis of older leaves.  Dark brown to black lesions develop on the surface of lower stems (Picture 1).  Vascular tissue may be brown. Adventitious roots may grow profusely from these symptomatic stems.  It may resemble that of bacterial canker.  This disease may affect the fruit as well (Picture 2).

 

 

Picture 1 Tomato pith necrosis lesions on stem 

Picture 2 Tomato pith necrosis symptoms in fruit

 
 
 
 
 
 
 

 

Growers should avoid using excessively high nitrogen rates, should not use overhead sprinklers on field tomatoes, and remember to sanitize pruning shears.  In field tomato, keep good crop rotation and control volunteer tomato and nightshade weeds.