Different Bio –agent Used for Controlling Weeds
Below are the different bios –agent used for controlling weeds
2) Carp fish
5) Fungi and
6) Competitive plants.
The long term experiments with great care are conducted for searching a host specific bio agent. The outstanding and feasible examples of biological control of weeds are given below:
1) Use of Insects:
a) Lantana camara ( Ghaneri) – was controlled by using Crocidosema lantana Busck, a moth as most promising bio-agent in Haweli- This bio-agent feeds on flowers and seeds.
Lantana bug ( Teleonemia scruplosa stall) was used in Australia for controlling Ghaneri.
Hispine beetles ( Octotoma scabripennis and Uroplate girandi were also used in Australia for control of Ghaneri.
b) Prickly pear/cactus (Opuntia spp) by using cochineal scale insects. ( Dactylopis indicus and Dactylopius tomentosus in south India and in Australia by using Cactoblastis cactorum.
c) Alligator weed ( Altermathere philoxoroides ) in U.S.A has been effectively controlled with flea beetle (Agasicles hygrophyla)
d) Fern (Salvinia molesta) in kerela (India) by using a beetle called Cytrobagous saviniae.
e) Cypenis rotundus (nustsedge ) in India U.S.A and Pakistan by Bacteria spp a shoot borer moth.
2) Use of Carp Fish:
Common carp ( Cyperus carpio) and Chinese carp ( White amur or grass carp) called Clenopharyngodon idella for control of aquatic weeds.
(Marisa cornuarietis ) and certain fresh water snails are useful to control aqutic weeds like water hyacinth, salvinia spp. and water lettuce.
4) Use of Mites:
A spider mite (Tetranychus desertorum ) was used in Australia foe control of prickly pear ( cactus).
5) Use of Fungi:
a) Acacia glauca was controlled in Hawali by injecting suspension of spare of cephalosporium spp.
b) Rhizoctonia blight for control of water hyacinth.
c) Use of Mycoherbicides / Bioherbicides.
Bioherbicides approach involves spray of specific fungal spores or its fermentation products , against the target weed. These preparations are called mycoherbicides ( Bioherbicides). Mycoherbicides can be specific (Selective) or non-specific (Non selective) and are used just like chemical herbicides in developed countries. Control of weeds by using the mycoherbicides is called bio-herbicidal control of weeds. Some commercial mycoherbicides in use abroad are as below:
A liquid suspension of fungal spores of Phytophthora palmivora.
Strangle Vine ( Morrenia odorata) in Citrus.
Wettable powder contaning fungal spores of collectotrichum spp.
Joint-Ventch ( Aeschymone spp)
A suspension of fungal spores of Bipolaris sorghicola.
Johnson grass (Sorghum helepense)
A microbial toxin produced as fermentation product of Streptomyces hygroscopicus
Non selective for killing generated vegetation.
6) Use of Competitive Plants:
a) Use of Rajagira (Amaranthus panjculatus ) for control of nutsedge ( nutgrass) and other weeds as it is the best smother crop and also produces allelopathic effect.
b) Use of smother crop like soybean, cowpea, greengram, Sanhemp, Sweet potato, etc. in crop rotation for control of weeds.
c) Proper crop rotation is helpful for management of crop associated and parasitic weeds.