Agriculture Reference
In-Depth Information
9.9.1 MECHANISMS THAT MEDIATE PEST CONTROL
Plants grown in inorganic fertilizers are more prone to pest attack than those
grown on organic fertilizers (Culliney and Pimentel 1986; Yardim and Ed-
wards 2003; Phelan 2004). Inorganic nitrogen fertilization improves the nu-
tritional quality and palatability of the host plants, inhibits the raise of sec-
ondary metabolite concentrations (Fragoyiannis et al. 2001; Herms 2002),
enhances the fecundity of insects dieting on them, attracts more individuals
for oviposition (Bentz et al. 1995) and increases the population growth rates
of insects (Culliney and Pimentel 1986; Jannsson and Smilowitz 1986).
Though organic fertilizer has an enhanced nutritional composition they re-
lease nutrients at a slower rate (Patriquin et al. 1995) hence plants grown
with organic fertilizers possess decreased N levels (Steffen et al. 1995) and
have higher phenol content (Asami et al. 2003) resulting in resistance of
these plants to pest attack. Similarly vermicomposts exhibit a slow, balanced
nutritional release pattern, particularly in release of plant available N, sol-
uble K, exchangeable Ca, Mg and P (Edwards and Fletcher 1988; Edwards
1998). Vermicomposts are rich in humic acid and phenolic compounds.
Phenolic compounds act as feeding deterrents and hence significantly af-
fect pest attacks (Kurowska et al. 1990; Summers and Felton 1994; QiTian
2004; Hawida et al. 2007; Koul 2008; Mahanil et al. 2008; Bhonwong et al.
2009). Soil containing earthworms contained polychlorinated phenols and
their metabolites (Knuutinen et al. 1990). An endogenous phenoloxidase
present in
L. rubellus
bioactivate compounds to form toxic phenols viz.,
p-nitrophenol (Park et al. 1996). Monomeric phenols could be absorbed by
humic acids in the gut of earthworms (Vinken et al. 2005). Uptake of soluble
phenolic compounds from vermicompost, by the plant tissues makes them
unpalatable thereby affecting pest rates of reproduction and survival (Ed-
wards et al. 2010a; Edwards et al. 2010b).
9.10 ROLE OF VERMICOMPOST IN NEMATODE CONTROL
It has been well documented that addition of organic amendments decreas-
es the populations of plant parasitic nematodes (Addabdo 1995; Sipes et
al. 1999; Akhtar and Malik 2000). Vermicompost amendments appreciably
suppress plant parasitic nematodes under field conditions (Arancon et al.
