[tomato] More on causes of sour rot in tomatoes

cvinson@mindspring.com (Tomato@GlobalGarden.com)
Fri, 13 Aug 1999 22:32:34 -0400

Marie's note about sour rot intrigued me, so I dug through my notes to
refresh my aging brain. Sorry for the poorly written post that follow; I am
cutting and pasting from my notes and it's been a long week! Anyway.....

Sour rot doesn't show up until the crop is ripening. This is because only as
sugars in the tomato rise, approaching 8%, does the environment for the
development of sour rot (aka Geotrichum citri-aurantii) develop.

The closer to ripeness, the more the susceptible the tomato fruit becomes
since near-ripe tomatoes are at their greatest level of susceptibility to
physical injury. Injured tomatoes (anything from insect/critter damage to
lesions caused by growth habit and environmental stress) are susceptible to
invasion by a wide variety of naturally-occurring fungi. The degree of
susceptibility is correlated to: a) the degree of injury; b) the overall
health and vigor of the individual plant; c) the genetic make up of the
variety, e.g., some varieties demonstrate more innate resistance than
others; d) the overall health of the environment in which the tomato is
grown (soil, water, balance of predators, etc.) For example, acetic acid
bacteria are one of the microorganisms causing sour rot in grapes (and other
crops). These bacteria are spread by vinegar flies which are in turn
attracted to the rotting clusters of fruit on the vine or ground (another
reason why good housekeeping is so vital in the garden).

Hopefully the above makes sense and doesn't contain any misinformation; if
not, apologies!

Catharine/Atlanta, zone 7b