(12 L ha
À1 ) with pendimethalin (0.5 g a.i. ha
À1 ) and S-metolachlor (1.0 kg a.i. ha
À1 )
reduced the density and dry biomass of horse purslane [159]. A reduction of 53–95%
was recorded in the weeds’ dry weight when sorghum water extract (10 L ha
À1 ) was
sprayed in combination with reduced doses of herbicides [160]. Various studies have
reported that the combined application of allelopathic water extracts in combination
with reduced dose of pre- and postemergence herbicides reduced the weed density
and dry biomass (Table 4).
4
Allelopathy for Insect Pest Management
Insects cause considerable damages to grain crops, fiber crop, legumes, and
vegetable crops. Insecticides have harmful effects on the environment and affect
the health and cause hygienic problems. Due to frequent and irrational application of
insecticides, the insects have evolved resistance against insecticides. In this scenario,
the use of secondary metabolites (i.e., allelochemicals) is the effective method to
control the insect pests (Table 5; [6]). There have been several advantages of these
metabolites such as easy handling, easy biodegradation, economical affordability,
and the environmental safety.
The chickpea beetle (Callosobruchus chinensis) is efficiently controlled by
application of secondary metabolites derived from olive, bhang (Cannabis sativa L.),
tea (Thea chinensis Sims), garlic (Allium sativum L.), black pepper (Piper nigrum
L.), and red chillies (Capsicum annum L.) [169]. The eucalyptus volatile oil was
useful for the control of rice moth (Corcyra cephalonica St.). Aphids and sucking
insects of Brassica spp. can be controlled by allelopathic water extracts from
mulberry (Morus alba L.), sorghum, sunflower, and mustard species [6]. The
strawberry aphids (Chaetosiphon fragaefolii; nymphs and adults) are controlled by
use of neem (Azadirachta indica A. Juss) seed oil [170]. The green cicadellid
(Jacobiasca lybica), whitefly (Bemisia tabaci), and Ashbya gossypii were controlled
by azadirachtin, an allelochemical extract from different parts of neem plant [168].
The conifer plantations provide shelter for large pine weevil (Hylobius abietis L.)
which can be managed by treating with neem oil. Azadirachtin, salannin, and nimbin
are the allelochemicals found in neem oil which help to control feeding weevil of
Sitka spruce (Picea sitchensis B.) [171].
The phenolics such as ferulic acid and p-coumaric acid can be used to control
wheat midge (Sitodiplosis mosellana G.) [172]. The mosquito (Culex pipiens L.) and
Mediterranean fruit fly [Ceratitis capitata (Wiedemann)] larvae are controlled by
common rue (Ruta graveolens L.), a fragrant plant that has coumarins and flavonoid
compounds. Cover crop residues enhance the nutrient level and allelochemical in the
soil that discourage plant pests, mainly diseases of soilborne pathogens [130, 131].
In a study, the larva of rice moth (Corcyra cephalonica St.) was controlled by the
application of eucalyptus volatile oils [166]. The allelopathic water extracts of
mustard, sunflower, and sorghum in combination with the mulberry extracts were
effective for managing the different sucking insects (e.g., aphid) in Brassica spp.
Sorghum and sunflower water extract were found to be more effective for aphid
mortality [77].
558
A. Nawaz et al.
À1 ) with pendimethalin (0.5 g a.i. ha
À1 ) and S-metolachlor (1.0 kg a.i. ha
À1 )
reduced the density and dry biomass of horse purslane [159]. A reduction of 53–95%
was recorded in the weeds’ dry weight when sorghum water extract (10 L ha
À1 ) was
sprayed in combination with reduced doses of herbicides [160]. Various studies have
reported that the combined application of allelopathic water extracts in combination
with reduced dose of pre- and postemergence herbicides reduced the weed density
and dry biomass (Table 4).
4
Allelopathy for Insect Pest Management
Insects cause considerable damages to grain crops, fiber crop, legumes, and
vegetable crops. Insecticides have harmful effects on the environment and affect
the health and cause hygienic problems. Due to frequent and irrational application of
insecticides, the insects have evolved resistance against insecticides. In this scenario,
the use of secondary metabolites (i.e., allelochemicals) is the effective method to
control the insect pests (Table 5; [6]). There have been several advantages of these
metabolites such as easy handling, easy biodegradation, economical affordability,
and the environmental safety.
The chickpea beetle (Callosobruchus chinensis) is efficiently controlled by
application of secondary metabolites derived from olive, bhang (Cannabis sativa L.),
tea (Thea chinensis Sims), garlic (Allium sativum L.), black pepper (Piper nigrum
L.), and red chillies (Capsicum annum L.) [169]. The eucalyptus volatile oil was
useful for the control of rice moth (Corcyra cephalonica St.). Aphids and sucking
insects of Brassica spp. can be controlled by allelopathic water extracts from
mulberry (Morus alba L.), sorghum, sunflower, and mustard species [6]. The
strawberry aphids (Chaetosiphon fragaefolii; nymphs and adults) are controlled by
use of neem (Azadirachta indica A. Juss) seed oil [170]. The green cicadellid
(Jacobiasca lybica), whitefly (Bemisia tabaci), and Ashbya gossypii were controlled
by azadirachtin, an allelochemical extract from different parts of neem plant [168].
The conifer plantations provide shelter for large pine weevil (Hylobius abietis L.)
which can be managed by treating with neem oil. Azadirachtin, salannin, and nimbin
are the allelochemicals found in neem oil which help to control feeding weevil of
Sitka spruce (Picea sitchensis B.) [171].
The phenolics such as ferulic acid and p-coumaric acid can be used to control
wheat midge (Sitodiplosis mosellana G.) [172]. The mosquito (Culex pipiens L.) and
Mediterranean fruit fly [Ceratitis capitata (Wiedemann)] larvae are controlled by
common rue (Ruta graveolens L.), a fragrant plant that has coumarins and flavonoid
compounds. Cover crop residues enhance the nutrient level and allelochemical in the
soil that discourage plant pests, mainly diseases of soilborne pathogens [130, 131].
In a study, the larva of rice moth (Corcyra cephalonica St.) was controlled by the
application of eucalyptus volatile oils [166]. The allelopathic water extracts of
mustard, sunflower, and sorghum in combination with the mulberry extracts were
effective for managing the different sucking insects (e.g., aphid) in Brassica spp.
Sorghum and sunflower water extract were found to be more effective for aphid
mortality [77].
558
A. Nawaz et al.