Question

Uncontrolled plant introduction is responsible for introduction of which weed in India

Answer 1

Parthenium hysterophorus L. (Asteraceae), a noxious plant, inhabits many parts of the world, in addition to its native range in North and South America and the West Indies [1]. According to Holm et al. [2] this noxious invasive species is considered to be one of the worst weeds currently known. This is a weed of global significance responsible for severe human and animal health issues, such as dermatitis, asthma and bronchitis, and agricultural losses besides a great problem for biodiversity. It is a widely held belief that the seeds of this weed came to India with grains imported from USA under the US PL 480 scheme, also known as “Food for Peace” which is a food assistance programme of the US government, and spread alarmingly like a wild blaze to almost all the states in India and were established as a naturalized weed. In India, the weed was first pointed out in Poona (Maharashtra) by Professor Paranjape, 1951, as stray plants on rubbish heaps and was reported by Rao [3] as a new species in India, but the earliest record of this species in India goes back to 1814 by Roxburgh, the father of Indian Botany, in his bookHortus Bengalensis [3, 4]. Ever since the weed became a menace around the globe including India, efforts have been made to manage the weed employing different methods such as mechanical, competitive replacement (allelopathy), chemical, and biological control methods. However, the weed has defied all human efforts to control it due to one or other disadvantages. Biological control, the intentional manipulation of natural enemies, insects, bioherbicides, nematodes, snails, and competitive plants to control harmful weeds, is gaining momentum as it is an effective and ecofriendly alternative to conventional methods of weed control [5].

Answer 2

Answer:

A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place". Examples commonly are plants unwanted in human-controlled settings, such as farm fields, gardens, lawns, and parks. Taxonomically, the term "weed" has no botanical significance, because a plant that is a weed in one context is not a weed when growing in a situation where it is in fact wanted, and where one species of plant is a valuable crop plant, another species in the same genus might be a serious weed, such as a wild bramble growing among cultivated loganberries. In the same way, volunteer crops (plants) are regarded as weeds in a subsequent crop. Many plants that people widely regard as weeds also are intentionally grown in gardens and other cultivated settings, in which case they are sometimes called beneficial weeds. The term weed also is applied to any plant that grows or reproduces aggressively, or is invasive outside its native habitat.[1] More broadly "weed" occasionally is applied pejoratively to species outside the plant kingdom, species that can survive in diverse environments and reproduce quickly; in this sense it has even been applied to humans.[2]

Weed control is important in agriculture. Methods include hand cultivation with hoes, powered cultivation with cultivators, smothering with mulch or soil solarization, lethal wilting with high heat, burning, or chemical attack with herbicides.