Expanding classical biological control of weeds with pathogens in India: the way forward.

Abstract

Invasive alien weeds are a major constraint in agriculture, forestry and the environment in India. Classical biological control (CBC) of these exotic weeds through deliberate introduction of arthropods is almost a century-old practice. History has recently been made with the successful introduction of the first plant pathogen, Puccinia spegazzinii de Toni, against mikania weed (Mikania micrantha H.B.K.) in India. With the mechanism in place for the importation, quarantining and release of pathogens, it is envisaged that more introductions will be made in the future. The agent under immediate consideration is Puccinia abrupta Diet. and Holw. var. partheniicola (Jackson) Parmelee against parthenium weed (Parthenium hysterophorus L.), generally considered as the worst terrestrial social weed in India. Down the line, other terrestrial weeds such as Chromolaena odorata (L.) R. King and H. Robinson and Lantana camara L. and aquatic species like Eichhornia crassipes (Martius) Solms-Laubach could be targeted for pathogens. This article, besides presenting an overview of the research that has gone into selection of candidate fungi for CBC of M. micrantha and P. hysterophorus, also analyses the infrastructure and expertise requirements for further expanding the target list.

Biology, ecology and management of the invasive parthenium weed (Parthenium hysterophorus L.)

“…India has become one of the most affected countries, with parthenium weed now occurring in all of its States and presenting a major problem in those States that have large areas of non‐cropped, rain‐fed land . This weed may have gained entry into India from the United States in a wheat ( Triticum aestivum L.) food grain lot imported into Pune in 1956 .…”

“…India has become one of the most affected countries, with parthenium weed now occurring in all of its States and presenting a major problem in those States that have large areas of noncropped, rain-fed land. 16 This weed may have gained entry into India from the United States in a wheat (Triticum aestivum L.) food grain lot imported into Pune in 1956. 17 However, a herbarium record from Dehradun suggests that at least one earlier introduction had occurred in the 1800 s. 18 Parthenium weed has now spread from India into most of its neighbouring countries.…”

Endophytes of Invasive Weeds:Pertinence to Classical Biological Control in India

“…Identification of the entire diversity of endophytes in different populations of these two weeds in India, and its comparison with the diversity in the native region, may give indica-tions on the performance or otherwise of potential natural enemies. Though the introduced rust pathogen, Puccinia spegazzinii, showed initial signs of establishment on M. micrantha in Kerala (Sreerama Kumar et al, 2008), it could not spread further. Do endophytes have a role in the M. micrantha-P. spegazzinii system?…”

“…A thorough understanding of the endophytic diversity of invasive weeds -which could be future targets for CBC in India (Sreerama Kumar et al, 2008) -is necessary for zeroing in on the right candidate bioagent. For instance, if Ambrosia psilostachya, which has been reported only from Tumakuru district of Karnataka (Prasad et al, 2013), were to spread widely, biocontrol options may have to be considered and an analysis of endophytes associated with the plant is warranted.…”

“…Therefore, where insects fail, other category of agents may offer control. In the case of Lantana camara, for example, the two rust species, Prospodium tuberculatum and Puccinia lantanae, may be considered (Sreerama Kumar et al, 2008). Of course, desired control of lantana weed has not been achieved through insects in most of the tropics, except Hawaii (McFadyen, 1998).…”