Late Blight – Myths and Misinformation

Allegory-of-immortality-1179

Late blight is the nemesis of tomato growers, especially in the damp climate of the coastal Pacific Northwest. Many sources of gardening advice include a lot of misinformation about managing late blight.  For authoritative sources of good information, I recommend:
Managing Late Blight.
Managing Late Blight in Organically-Produced Tomatoes

Myths –

  • Crop rotation is essential because late blight spores survive in the soil over winter. False. Currently, in the US, the late blight pathogen can only survive on living host plant tissue. This is because blight fungi have two different modes of reproduction, only one of which is presently observed in the US. Late blight can reproduce either sexually, or asexually. Sexual reproduction requires the presence of both A1 and A2 mating types (equivalent to male and female sexes). Sexual reproduction produces oospores, which can survive over the winter, in soil for example.  However only the A2 mating type (sex) exists in most of the US.  Therefore, late blight can only reproduce asexually. Asexual reproduction produces zoospores, which are much less hardy than oospores, and can only survive for a few hours outside of living host (tomato or potato) tissue.
  • Seeds from late blight infected tomatoes will produce infected plantsFalse. Late blight zoospores do not survive on tomato seeds.
  • Stakes used for tomatoes must be disinfected before re-use to prevent spread of late blight. False. Zoospores cannot survive for more than a few hours on solid surfaces such as stakes.
  • Late blight infection is caused by spores present in the soil, so contact of tomato plant leaves with the soil must be prevented. False. Zoospores cannot survive in soil. Zoospores are spread almost entirely by air-born dispersal of spores released by living infected plants.

Starts started (II)

In my last post I touted my cable-heated gravel bed for starting plants. Forget that – my Gro-Quick 48 Ft Soil Heating Cable failed after only one season of use.  Thanks to Gro-Quick my starts are about a week behind where they should be. In the end, to get them started, I put a couple lamps with IR heating bulbs above my plants.  All but two of my 126 varieties are now sprouted.

Baby heirlooms
Baby heirlooms

 

It’s time to sow tomatoes!

I have used various systems to decide what date to sow tomatoes.  Choosing the correct date for indoor sowing requires predicting how soon consistently warm weather will arrive in the Spring, and this varies tremendously from year to year.  This year I have adopted a new system  I sow when my dog Lucy starts to actively shed her winter coat.  Today’s the day!

Lucy looses her fur
Lucy looses her fur

Csikos Botermo

Tomatofest lists this Hungarian heirloom as a late maturing variety and says Csikos Botermo translates as “striped good cropper”. Abundant Acres indicates it is an early variety and suggests the name as “early variety of Hungarian cowboys”. The only thing they agree on is that the fruit is striped. Although I prefer the colorful Abundant Acres translation, I am afraid Tomatofest has it right as Google Translate indicates that “csíkos bőtermő” means “striped, high yielding”. On the other hand, I must agree with the “early” designation by Abundant Acres. This year, Csikos Botermo was the 4th earliest variety to ripen in my collection of 118 varieties..Csikos Botermo

First Fruit

118 tomato varieties presently growing and the first two varieties to bear fruit are …………….(drum roll)………….. Purple Russian and Indische Fleisch.  Oddly, neither of these varieties was advertised as being particularly early – both are listed as mid-season varieties. But I have noticed before, tomato varieties respond in unpredictable ways to our odd Puget Sound climate.

Purple Russian and Indische Fleisch

Happy tomatoes

DSC_0053I don’t know whether to credit global warming, or my new regimen of growing my tomatoes vigorously pruned and trained to vertical posts, but this is the first time in many years I have made it to the first of July without any sign of late blight.  Growing tomatoes trained in this way prevents ground contact and improves air circulation – both helpful in preventing attack by the blight fungus.  In the Puget Sound region  we invariably have a number of days of cloudy, moist and relatively warm weather in June, which the blight fungus loves.  This year my tomatoes survived June unscathed and in phenomenally  good shape.  The majority of my 120 varieties of tomatoes already have fruit.  Shown below is Alicante, a British variety, which fruits early and productively, even in cool climates.

alicante

Training tomatoes

The key to training tomatoes to a vertical support is illustrated in the picture below.
before after prune

Tomato plants branch by growth of buds that form at the Y between two existing branches.  The bud in the upper panel has been removed in the lower panel by simply pinching it off.  These buds grow amazingly fast in warm weather, so buds need to be removed weekly.  Left unchecked, each bud forms a branch that will form more buds and branches, so the number of vines grows exponentially, from 2 to 4 to 8 to 16, etc. If you remove buds properly you will end up with a  single vigorous vine, which will easily grow 6′-8′ or more up a support.

A high stakes proposition

This year, for the first time, I am training my tomatoes on tall stakes.  This involves frequent pruning of the plants to remove the buds that form at branch nodes, so that the plants grow as one or two long vines, tied to bamboo poles at 10 inch intervals.  The process of pruning and tying 120 different plants takes much less time than I imagined it would.  In theory, growing plants vertically in this manner will improve air circulation around the plant, to reduce the possibility of the plants developing late blight.  I must say, the plants look wonderously healthy so far, so fingers crossed.stakedtomatoes