Biological and control of the weed Mikania micrantha HBK in Kerala
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Date
1999
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Department of Agronomy, College of Horticulture, Vellenikkara
Abstract
Mikania micrantha is a recently introduced weed spreading fast in agricultural
and non-agricultural areas of Kerala. It is commonly known as mile-a-minute weed
in English and as American vally, Padvayara etc. in Malayalam. A study on "Biology
and control of the weed Mikania micrantha HBK in Kerala" was undertaken at the
College of Horticulture, KAU, Vellanikkara during 1995-1999 to study the
distribution, biology, competition to crops and alternate uses of Mikania and also to
develop recommendations for controlling the weed.
Infestation of Mikania was found to be widespread in Ernakulam and Kottayam
districts and in most parts of Trichur, Idukki, Alappuzha and Pathanamthitta districts.
The weed has not yet spread to the southern districts, with no infestation in
Thiruvananthapuram and only isolated incidence in Kollam district. In the northern
districts of Malappuram, Palakkad, Kozhikode, Wynad, Kannoor and Kasaragod, only
isolated infestation was noticed.
Mikania is a fast growing herbaceous perennial climber belonging to the family
Asteraceae. The weed seeds germinated in April-May, flowered in October and took
9 to 12 days for seed maturity. Inflorescence is an umbel of heads. Average seed
output per plant was 45812 with an average production of 357 inflorescence, each
having 32 flowers (four seeds per head). Fresh seeds gave 80 per cent germination
and the viability decreased to zero after seven months of storage.
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The weed can propagate by seeds and stem . cutti ngs. Seeds kept for
germination on the soil surface (0 cm depth) gave maximum germination, whereas
even the slight burying of the seeds prevented germination. From the stem cuttings,
maximum establishment was for the cuttings from the basal portion of stem when
planted at zero depth of planting followed by middle and apex portio . Sprouting per
cent decreased with depth of planting with no sprouts arising when planted at 5 cm
below the surface. No sprouts were produced from internode at any depth
of planting. Leaves did not sprout, but the leaf petioles with axillary bud
produced sprouts.
Competition from Mikania suppressed the growth of pineapple, banana,
rubber, coconut, cocoa and teak plants. It also delayed the flowering and reduced the
fruit weight of pineapple and banana.
Among the. physical methods of control, digging at monthly interval was found
to be the best followed by digging at bimonthly interval, sickle weeding at monthly
interval and sickle weeding at bimonthly interval.
Pre emergence herbicides, diuron 0.5 kg ha") and oxyflourfen (0.20 kg ha:')
resulted in prevention of germination and establishment of Mikania followed by
atrazine, butachlor, metolachlor, alachlor, pretilachlor and fluochloralin.
All forms of 2, 4-D resulted in complete drying of Mikania. Even the lowest
dose (0.25 kg ha') tested gave 92-99 per cent control of Mikania. Other herbicides
in the order of effectiveness were glyphosate, glufosinate ammonium and paraquat.
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Eighteen insect pests were found infesting Mikania. The major pests were
aphid, tea mosquito bug, thrips and the lepidopteran pest, Spilosoma obliqua.
However, since all these insect pests are polyphagous in nature, their utility for
biological control is limited.
Pathogens infecting the weed were identified as Colletotrichum
gloeosporioides, Alternaria alternata, Curvularia lunata Var. aria and Corynespora
cassicola. The toxic metabolites (both endotoxin and exotoxin) isolated from
Colletotrichum sp. and Alternaria sp. produced necrotic symptoms on Mikania. Size
of the leaf spot increased with time leading to complete drying of the leaf
by four days.
Biornass yield of single Mikania plant was 2.25 kg fresh weight (18.25 % dry
weight). Under natural field condition biornass yield from one square metre area was
2.012 kg fresh weight. Average increase in the length of vine per day was 6.29 cm.
The mean content of different nutrients in Mikania was 2.35 per cent N, 0.39 per cent
P, 3.58 per cent K, 0.82 per cent Ca, 0.42 per cent Mg, 0.013 per cent Mn, 0.167
per cent Fe, 0.0045 per cent Cu and 0.022 per cent Zn.
Rate of decomposition of Mikania was faster during the initial period and
decreased towards the end of the study, reaching almost 100 per cent decomposition
by one year.
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Fodder value was studied by estimating the chemical composition and fibre
fraction of Mikania. It contained an average of 14.63~ cent crude protein, 2.36
per cent fat. ~:3.2 per cent crude fibre, 48.75 per cent nitrogen free extract, 8.92 per
cent ash, 0.87 per cent calcium and 0.42 per cent phosphorus. The fibre fractions
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contained 42.42 per cent neutral detergent fibre, 33.22 per cent acid detergent fibre,
0.096 per cent cellulose, 9.2 per cent hemicellulose and 10.84 per cent lignin. The
analysis for anti-nutritional factor hydrocyanic acid showed negative result.
Allelopathic effect of Mikania when used as mulch or incorporation as well
as the effect of the Mikania extract were studied using the test crops, rice, cowpea and
rubber. Mikania had an inhibitory effect on growth of rubber, but the growth of rice
was enhanced by its application. Treatment with Mikania extract did not have any
influence on germination and radicle length of rice seeds where as in cowpea seeds
the allelopathic effect was very much pronounced.
Description
PhD
Keywords
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Citation
171615