Many growers try to plant warm season vegetables earlier to take advantage of high early season prices. Unfortunately, the chances of transplanting crops like tomatoes, peppers, and cucurbits into field conditions favorable to damping off is increased, even if using good practices like raised beds covered with plastic mulch and protected by floating row covers. This spring’s fluctuating temperatures (often on the cool side), along with cloudy and rainy conditions, further aggravate the situation. So what is damping off and what can you do about this situation?
Damping-off generically refers to seedling diseases from a number of fungi including species of Pythium*, Phytophthora*, Fusarium**, Rhizoctonia**, Sclerotinia**, Sclerotium**, and Botrytis**. It is often associated with germinating seeds and young seedlings, which are vulnerable to attack by these pathogens during periods of unfavorable growing conditions- damp, cool, and low light conditions.
** True fungi
The best control of damping-off for early transplanted warm season vegetables is to start with disease free transplants and clean growing media. Once this disease has started in a seedling flat, it may be difficult or impossible to control or determine if ‘healthy looking plants’ are uninfected. Treating transplants before field planting should be considered in these situations:
What fungicides are available to use? Unfortunately two common broad spectrum fungicides are no longer labeled for vegetables- Captan and Banrot. Synthetic products available are Terraclor (PCNB), Ridomil (mefenoxam), Previcur Flex (propamocarb ), and Ranman (cyazofamid). Ridomil and Ranman are currently labeled for cucurbits and fruiting vegetables, but Previcur Flex is only labeled for cucurbits. Ridomil (mefenoxam), propamocarb (Previcur Flex), and Ranman are effective only against Oomycetes (Pythium and Phytophthora), but will not control any of the ‘true fungi’ damping off species (see 2nd paragraph above). Terraclor can provide protection against Rhizoctonia diseases. Another option is the biologically based fungicides, which are generally considered better at preventing diseases than curing them. Streptomyces griseovirdis (Mycostop), Trichoderma virens (SoilGard), and Trichoderma harzianum (RootShield), Basillius subtillis (Companion) are biological controls that are labeled for vegetables, including organic production.
A few of good questions are:
REVISED: December 1, 2015