pests and diseases
Fusarium wilt

Photo of soil tomato plant with Fusarium wilt.
The tomato plant in the centre is most likely suffering from Fusarium wilt.  I say probably as there are a number of soil bourn fungal diseases that show similar symtoms.
Fusarium Wilt is caused by the fungal pathogen Fusarium oxysporum.  It effects tomatoes, legumes, cucurbits, and sweet potatoes sweet potatoes.  The symptoms include wilting, chlorosis, necrosis, premature leaf drop, browning of the vascular system, and stunted growth. It is a soil pathogen that feeds on dead and decaying organic matter and survives in soil debris.

It is spread short distances by water splash and on garden tools, and long distances by infected transplants and seeds and in contaminated soil brought into your garden.  While it can survive in a range of conditions in does best in warm moist soils.

For more details see the Fusarium Wilt entry in Wikipedia.

Once in the soil Fusarium Wilt is difficult to eradicate.  The best defence is to try and not introduce it to your vegetable garden in the first place.  Do not transplant any plant that looks like it has the disease and avoid bringing in soils from other gardens.  If it is introduced to your garden then below are steps you can take to control it.

  • If possible do not plant vegetables susceptible to  Fusarium Wilt for at least three years.
  • If planning vegetables that are susceptible in a bed known to be contaminated with it then keep the watering to a minimum, the dryer the soil the less likely that the pathogen will spread.
  • Avoid using wicking beds as they create the warm moist conditions that pathogen thrives in.
  • If growing plants that are susceptible to Fusarium Wilt then choose varieties that have some resistance to it.

Note that there is a number of soil bourn fungal diseases that affect vegetables and they generally show similar symptoms to Fusarium Wilt.  They are however usually treated in a similar fashion.