ESTABLISHMENT OF APRICOT AND ALMOND TREES USING SOIL MULCHING WITH TRANSPARENT (SOLARIZATION) AND BLACK POLYETHYLENE FILM - EFFECTS ON VERTICILLIUM WILT AND TREE HEALTH
Jj. Stapleton et al., ESTABLISHMENT OF APRICOT AND ALMOND TREES USING SOIL MULCHING WITH TRANSPARENT (SOLARIZATION) AND BLACK POLYETHYLENE FILM - EFFECTS ON VERTICILLIUM WILT AND TREE HEALTH, Plant Pathology, 42(3), 1993, pp. 333-338
Apricot (Prunus armeniaca) and almond (P. dulcis) trees at the first l
eaf stage were planted in soil infested with Verticillium dahliae and
mulched with transparent or black polyethylene film, or not mulched, i
n the San Joaquin Valley of California, March-August 1990. During the
19-week mulching treatment, summer soil temperatures reached as high a
s 46, 41, and 33-degrees-C at 18 cm depth; and 41, 37, and 32-degrees-
C at 30 cm depth under clear film, black film, and no film, respective
ly. Trees mulched from the time of planting with transparent polyethyl
ene (solarization) did not survive or grow as well as those mulched wi
th black film or not mulched. Incidence of foliar symptoms due to Vert
icillium wilt was reduced by 86-100% in both apricot and almond trees
by black, as well as transparent film mulch the following season. Inci
dence of vascular discoloration symptoms of trunks and primary scaffol
ds due to Verticillium wilt was similarly reduced by both mulches. Mul
ching with black polyethylene film gave better overall results than so
larization with transparent film. The intermediate soil temperatures p
roduced did not chronically harm trees, as judged by tree survival and
annual growth of trunk diameter, yet the prolonged period of soil hea
ting provided control of Verticillium wilt equivalent to that of solar
ization with transparent polyethylene. These studies provided further
evidence that in-season mulching can be used to conserve water during
establishment of new orchards or replant trees in warm, arid climates.