Review of the book "Parthenium Menace in the Indo-Myanmar Hotspot Region"
Dr Ricardo Labrada *
This book (written by Nameirakpam Irabanta Singh, Biman Kumar Dutta and Yumnam Ngangthoi Devi and published by LAMBERT Academic Publishing, Germany) presents extensive information on the harmful effects, especially allelopathic, of Parthenium hysterophorus (PTNHY) weed, in the conditions of the Indo-Myanmar region, which appear in the first two chapters of the book, while the third and fourth chapters address the effect of different plants on this weed as a method for its biological control.
The main approach of the conducted studies has been to determine the effect of dry masses of PTNHY or extracts of parts of their organs on various plants, and vice versa of plants such as Amaranthus spinosus, Senna tora (L.) Roxb. (There called Cassia tora) and Cassia sericea Sw. on the growth of PTNHY.
Both types of studies provide valuable information, which confirms the invasive character of PTNHY, its adverse effects in the agriculture, as well as its allelopathic toxic effect over the surrounding plants, where they grow and interact.
The option to eliminate the presence of the weed planting another species, perhaps more competitive and/or allelopathic in a way not to leave empty space for weed growth and development, is really reasonable, moreover, that such an approach may prevent the use of toxic chemicals, some of them tolerate to some extent by PTNHY.
The information provided in the book indicates that high dissemination of PTNHY in the conditions of Indo-Myanmar region, confirming the aggressive distribution of this species in most parts of Tropical and Sub-Tropical Asia. Even its polyploidy may provide its evolution and adaption to temperate climate areas, something already observed in the fields of China and South Korea.
Consulted literature was extensive; it covers 351 bibliographical sources, which enabled the authors to compare their results with others previously obtained by researchers of other institutions.
Conclusions and recommendations are all reasonable. We all agree that it is essential to organize an awareness campaign for the population to know of the damage PTNHY may cause only to the agricultural fields, but even to public health.
A detail noticed in the text, the authors assert that PTNHY can have even a complete cycle of 90 days and no source of this result is provided, which is highly doubtful. In the conditions of the Caribbean, where this plant originates from, its flowering begins regularly after six weeks of its emergence, and the whole cycle lasts up to five months and more, so it is recommended that this statement be reviewed and if data is available, inform about it.
The other aspect not taken into account is the one related to PTNHY C/N and other plants chosen for the control of the weed.
When organic matter decomposes, nitrogen usually experiences two different stages of mineralization and immobilization. Mineralization of nitrogen means that nitrogen is decomposed into plant accessible form such as NH4+ (via ammonification) NO3 (via nitrification). Immobilization of nitrogen occurs when the accessible nitrogen species are taken up by microorganisms preventing them from being accessible by plants.
The rate and extent of Nitrogen immobilization are related to the biochemical composition of the compost. A high C/N ratio in soil-incorporated mass will promote nitrogen immobilization.
PTNHY C/N ratio should be more than 20, which is relatively high, and the effect seen after its mass incorporation could be rather related to nitrogen immobilization than to immediate allelopathic effect, i.e., release of substances from roots and stems causing plant toxicity.
This effect can be also achieved incorporating mass of A. spinosus and Casssia spp. In areas infested by PTNHY. Therefore, the authors are invited to study this aspect in coming studies.
The other aspect is the use of weeds to combat a weed. PTNHY is a very harmful species, so the same we can assert for Amaranthus spinosus. If this approach is to be adopted, it is necessary to have a clear idea of how to combat these species to avoid high infestations in the field. In this context, it would be feasible to study the effect of various crops to this end or their mixtures.
In conclusion, this book is an important source of data on PTNHY damage and possible ways to control it, which can be well used by students, researchers and technicians dedicated to weed management.
* Dr Ricardo Labrada wrote this article for The Sangai Express
The Reviewer is ex-technical agricultural officer, FAO, Rome,
and in charge of the area of Weeds in that organization (1990-2009)
This article was webcasted on June 26 2024.
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