Department of Plant Pathology, Punjab Agricultural University, Ludhiana-141004
National Symposium on Strategic Issues in Plant Pathological Research held at Department of Plant Pathology, CSK HP Krishi Vishvavidayalaya, Palampur on November 24–25, 2011
The use of fungicides has assumed importance over the years in the control of more damaging plant pathogens against which host resistance is not easily available or is unstable, particularly for polycyclic oomycete pathogens. In some cases, the benefit gained through fungicide use is more critical to the extent that certain crops, such as potato, grapes and rubber, to name a few, can not be cultivated in the absence of disease control that remains heavily dependent on the use of fungicides. The process of fungicide discovery for managing Oomycete caused diseases has undergone a significant change over the years. After the era of broad spectrum multisite fungicides and site-specific systemic fungicides, notably phenylamides, several novel action fungicides of different chemical classes have been developed in the past two decades. These are more ecofriendly and used at a much lower dose rates as compared to the earlier compounds. Most noted among these are the strobilurins (QoIs), derived from Strobilurus tenacellus, a wild mushroom. These are analogues of strobilurin-A and have a wide range of disease control. Azoxystrobin was the first strobilurin introduced in 1996 and currently nine strobilurin compounds are available. Other important fungicides introduced for the control of Phytophthora and related Oomycete pathogens in the last decade are Oxazolidinediones (famoxadone), Imidazoles (fenamidone), Benzamides (fluopicolide, zoxamide), Valinamides (iprovalicarb, benthiovalicarb), Mandelamides (mandipropamid), Cyanoimidazoles (cyazofamid), and Thiocarbamates (ethaboxam) representing different chemistries and mode of action. The main advantages of new generation compounds are that these ae ecologically safer and are required to be used at a much lower dose rates that their earlier counterparts. Prominent among those being tested against different Phytophthora caused diseases in India are mandipropamid, iprovalicarb, benthiovalicarb, fluopicolide, famoxadone, cyazofamid, pyraclostrobin and kresoxim methyl. The role of recently developed anti-Oomycete fungicides in disease control will be discussed. One of the main limitations of new generation fungicides is their single-site mode of action that may lead to resistance build up in target pathogens. Rapid development of resistance to strobilurins is now well documented and these need to be used in prepacked mixtures. The use of new generation fungicides needs to be regulated and FRAC guidelines adopted so as to maintain their efficacy levels.
