Death Valley

Ok that may be a bit of an exaggeration – but my garden is in a valley and there has been death – three so far and by the end of the season I suspect there will have been twenty with a complete tomato population wipe out.  The only advantage I can see is I will still get some tomatoes although from what I have read, they won’t be as “tasty”.

I have a disease.  To give it its full name:  Pith Necrosis.  And to be honest I’d never heard of it until today and it isn’t one of the big three problems that strike tomatoes in their prime.  You normally think of Blight, Blossom End Rot (which isn’t a disease but a nutrient availability issue) and the dreaded TTP Tomato Potato Psyllid.  I have a problem solver book that lists 22 things that could possibly go wrong with tomatoes, and Pith Necrosis isn’t there!  It wouldn’t surprise me if it was rare, we’re always getting some kind of rare problem around here – nothing that will kill us mind you.

I discovered the problem yesterday, unintentionally, but in doing so may have made it a whole lot worse.  I have been diligently spraying my tomatoes for the Psyllid every two weeks ever since I discovered those first tiny eggs clinging to the edge of a leaf.  I have been taking care of the needs of the tomatoes on a Monday as they are in sector one and doing the spraying then.  But last time I wasn’t able to do it on a Monday and couldn’t remember for the life of me if I had done it on a Tuesday or a Thursday and decided to wait until the next Monday to get back into routine.  But my goodness, those horrid little bugs didn’t wait for me…  there was quite the infestation, and plenty of green vegetable bugs to boot.

So, I grabbed the nearest secateurs and removed infested foliage and tied in wayward branches, making it easier to penetrate the tops and bottoms of the leaves with spray.   Before spraying I did a hard pick of anything that may come ripe in the next 7 days for the withholding period, which will probably save them from the ravages of the green vegetable bug.  There weren’t many but I thought that was because of the Psyllid.  Oh, how I was mistaken.

While I was at it, I decided to remove the plants that were clearly dead.  I knew it wasn’t the Psyllid but thought it was a stem borer as it looked a little munted at ground level.  Not only did I pull them out, but I chopped them up to make it easier to fit in my weed bucket.  Little did I realise what harm I was doing.  I was spreading disease!

You see – Pith Necrosis is a bacterial disease and Pseudomonas corrugata is responsible.  If I remember back to the days of my microbiological training, many moons ago, Pseudomonas was one of those ubiquitous bacteria that are found everywhere and if you didn’t know the answer to a question in a test or exam – if you wrote Pseudomonas down there was a high chance you’d get a point for getting the genus right.

This particular species lives in the soil and takes advantage of weak tomatoes in the perfect storm of weather conditions, with a little bit of help from an unwary gardener.

Firstly, as a bacterial disease, it is spread easily through contact and if you remove the lateral from one plant and then move on to the next plant without washing hands or sanitising tools, then you are spreading disease.  I should have known better.  It is microbiology basics drummed into students from day one.  I will no longer do or recommend pinching out laterals.  It is best to do it with clean, sharp secateurs and sanitised in between with a small spray bottle of meths.

The main reason my tomatoes were weak is my fault…  I wanted them to grow fast as they went into the garden late and so when they shot up, I thought nothing of it.  It turned out they shot up because there was too much nitrogen in the soil.  This causes fast but weak growth and makes them a target for all sort of pest and disease that can sense weakness.  But all that lush green growth looked healthy.

The first mistake I made was I thought I was doing a good thing following the tomatoes with the peas – a nitrogen rich soil must be good – right?!  Then I grew a cover crop to return organic material to the soil – only the best for my plants.  Once that had been dug in and allowed to rot down, I added compost, blood and bone, sheep pellets and Dynamic Lifter – all according to the instructions.  However, there should be instructions that says “when used in conjunction with…  then use this much…”

For the home garden it is difficult to know what state the soil is actually in as soil testing in a laboratory is cost prohibitive.  To test each of my beds individually would be well over two thousand dollars.  And there aren’t any effective home test kits readily available here – although under the circumstances I may need to investigate this further.  So, what is left is trial and error.  You know you need to replace the nutrients taken by the plant and tomato plants are big there for it makes sense to give the soil lots of love.  However not all plants have the same needs.  Corn is a big tall hungry plant and would love the preparation I prepared for the tomatoes.  Carrots on the other hand don’t like too much nitrogen and would split at the thought of it.

So, I will ease up on the additional material going into the garden and rearrange my crop rotation – again – to put the corn before the tomatoes instead of the peas.  I was going to move the corn into that cycle anyway to benefit from the shelter provided by the wind break along the fence.  I just need to make sure where I put them fits in with the timing of the early starters and the slow pokes who languish in the beds too long.  It is a bit of a puzzle.

The last part is out of my control – the weather.  Cool night time temperatures, high humidity and wet conditions are the final factors that encourage this disease.  And that dodgy spring and early summer we had would have been perfect conditions for a bunch of rampaging Pseudomonas to go off looking for a nice juicy stem to climb into.  If only I could control the weather…

So next season – I will have a gentle hand when preparing the soil, I’ll pop them into the bed where the corn once was, which will mean the corn will be where the tomatoes have been and before the peas.  This arrangement should suit everyone.  I will be slow to grow my tomatoes – there is no hurry and hope they respond by growing slowly.  I will take garden hygiene more seriously and I will pray the weather is better suited to avoiding this problem.

As a gardener you are always learning and boy have I just had a major lesson.

Come again soon – I’ll come up with something less gloomy.

Sarah the Gardener  : o)

NB:  Thanks to the experts at Yates NZ who diagnosed the problem for me.