Tomato Blossom End Rot

Most of us have experienced some form of tomato blossom end rot (BER). And lately I have noticed a few people experiencing varying forms of severity of this on their crop this growing season.Last season I personally noticed not a sign of BER, but have noticed a few mild cases of it this year despite having put the hard yards into soil preparation.

Blossom end rot (BER) in tomato

Did you know that the scientists are still researching this issue and that in fact it is not yet a resolved case!!! People who blame a lack of calcium uptake would be correct to some degree, but it is not as simple as that. A study by Saure (2001) found that BER is not caused by a single factor of calcium (CA) uptake, but rather is a sequence of two equally important factors.

(1) a higher susceptibility to various stresses due to an increase in physiologically active plant hormones that influence the development process and a resulting decrease in Ca ions, causing the enhanced permeability of cell membranes,  and
(2) some kind of stress, e.g. by soil water deficit, high salinity, or high NH₄⁺ activity, causing the deterioration of cell membranes with subsequent loss of rigidity of cells.

BER seems to occur when stress exceeds stress tolerance, most frequently in young fruit at the beginning of cell enlargement. At this stage, usually the highest amount of physiologically active plant hormones and the lowest amount of Ca are found, i.e. stress tolerance is lowest.  Calcium per se is considered neither a primary nor an independent factor in the development of BER.

Nonami et al  2004 did a study on Calcium metabolism in tomato fruits. They found that calcium deficiency in fruits may not be the direct cause of occurrence of blossom-end rot in tomato plants. When two varieties of tomato plants were compared for Ca ion uptake abilities, it was found that occurrence of blossom-end rot was unrelated with the Ca absorption. This suggests that occurrence of blossom-end rot is related to metabolic disorder regulated with gene expression under stress conditions.

There is much out there to read in the scientific paper world, however what now seems to be the case is that the growing environmental conditions has a large part to play, and in our case it is the dry spell. We have had some cool and very hot days with some very dry conditions, humidity has ranged from high to very low. Sub soil has all but dried out even if you have been watering every day. And from my readings, even allowing tomatoes to dry out for 3 days, combined with the weather or a sudden day of 10mm when we have had so little can aide in the formation of BER.

So what to do???

The good news is you can still get good tomatoes if you mulch & address water issues. Be sure to mulch with a material that allows water to slowly penetrate into your soil. This type of mulch makes what water you receive from nature available longer to your tomatoes - a thick layer of straw, newspaper, or wood chips will do the trick.And water the soil before laying the mulch!!!!!  Next year, plan to space your tomato out more. a spacing of 1.5m (less for bush types) between each plant would allow the root of each plant to not compete and allow a much wider zone of tolerance if the weather is varied and dry. This spacing sounds like a lot and is unrealistic to most people, but one high yielding healthy plant is better than four poorly performing plants.

If you've seen Blossom End Rot in your garden this year and are doing everything else right, be sure to check your soil pH. If your pH is below 6.5, add some lime to raise the level as too acidic soil can affect the plants ability to uptake calcium. But test your soil first!!!