Agriculture Reference
In-Depth Information
(Davis, 1991; Davis
et al
., 2008). The list of pathogenic fungi which are controlled
by solarization includes many key pathogens, such as
Verticillium, Rhizoctonia
and
Fusarium.
The fi rst focus of solarization was aimed at controlling diseases caused by
pathogenic fungi, such as Verticillium wilt in eggplants and tomatoes (Katan
et al.,
1976),
Fusarium wilt in cotton (Katan
et al.,
1983) and Rhizoctonia in potatoes (Elad
et al.,
1980). The wide spectrum of pathogen control was evident in the early days of solariza-
tion when combined control of both
V. dahliae
and
Pratylenchus thornei
was achieved in
potatoes, along with a 33% increase in yield and successful weed control (Grinstein
et al.,
1979). Similar results regarding the control of Verticillium wilt were observed by Davis
& Sorensen (1986) in Idaho.
The heat-tolerant pathogens
Monosporascus cannonballus
and
Macrophomina
phaseolina
are not controlled by solarization.
Fusarium oxysporum
f. sp
. dianthi
is also
considered one of the wilt pathogens that is not easily controlled by solarization (Tjamos
et al.,
1999).
The control of phytopathogenic bacteria by solarization has only been reported in a
relatively few cases. Soil-borne
bacteria, including
Agrobacterium
and
Streptomyces
,
are among the bacteria controlled by solarization.
Streptomyces scabies
is an important
pathogen
of potatoes and peanuts, which has also been reported to respond to solariza-
tion (Davis & Sorensen, 1986; Grinstein
et al.,
1995). Solarization for 8 weeks in tomato
plastic houses drastically reduced symptoms caused by
Clavibacter
michiganensis
ssp.
michiganensis
(Antoniou
et al.,
1995). Solarization reduced populations of Gram-positive
bacteria by 64-99% (Stapleton & Garza-Lopez, 1988). It has been shown in a detailed
study in Oregon that
Agrobacterium
spp. population densities declined within solarized
plots and incidence of crown gall on cherry root stock planted in solarized soil was
reduced signifi cantly (Pinkerton
et al
., 2000).
Negative effects, due to control of benefi cial
rhizobia, have also been reported (Abdel-Rahim
et al.,
1988).
Many phytopathogenic nematodes are controlled by solarization (Stapleton &
Heald, 1991). Reports of effective control of nematodes for a short time, such as in
annual crops, are well established. The effi cacy of solarization for long-term suppres-
sion of nematodes, such as in perennial crops, is inconclusive. Certain nematodes, such
as the root knot
Meloidogyne
sp., are not always effectively controlled by solariza-
tion. However, ectoparasite nematodes such as
Pratylenchus
and
Ditylenchus
are well
controlled (Grinstein
et al.,
1979; Siti
et al.,
1982). Many phytopathogenic nematodes
cannot survive at temperatures above 40
o
C, and solarization therefore kills them in the
upper soil layers, but not necessarily at depths below 40 cm. One of the most impor-
tant, and as-yet unexplored, factors in nematode suppression is their upward migration
from the deep soil layers to the root zone following plant establishment during crop
growth. This effect might be connected with failure of nematode control by SH and other
disinfestation methods.
Solarization has been found to be effective in reducing the viability of various weeds.
The spectrum of controlled weeds includes species of winter and summer annual weeds
(Elmore, 1991; Cohen & Rubin, 2007). A parasitic weed of the genus
Orobanchae
was
controlled by solarization, (Jacobsohn
et al.,
1980; Abdel Rahim
et al.,
1988). Similar
results were obtained in the laboratory with the parasitic weed
Striga
(Elmore, 1991). In
contrast, differential responses are achieved with solarization in perennial weeds. Weeds
from the genus
Cyperus
are inconsistently controlled by solarization (Elmore, 1991).