Articles
BURIED DRIP IRRIGATION REDUCES ALTERNARIA LATE BLIGHT IN PISTACHIO
Article number
449_47
Pages
335 – 340
Language
Abstract
Alternaria late blight (Alternaria alternata) (A.a.), a fungal disease associated with high orchard humidity, threatens large pistachio production areas of California.
This disease affects both leaves and nuts.
Lower marketable yields due to reduced shell splitting and shell staining are the usual consequences of the disease.
This problem is most severe in flood irrigated (FI) orchards with infiltration problems and no chemical control method is currently available.
We theorized that changing orchard atmospheric conditions by reducing surface wetting could lessen A.a. damage.
The effects of buried drip (BDI) and FI on A.a. of pistachio were compared in a 32 ha mature pistachio orchard ("Kerman" on P. Integerrima) for two seasons.
BDI resulted in shorter periods of dew formation per day, lower relative humidities, and higher temperatures.
This, in turn, reduced the incidence and severity of infected leaves by A.a.
For instance, about 10 and 55% of the leaves in the BDI and FI, respectively, were infected at harvest.
Furthermore, BDI reduced the incidence of A.a. infected fruit by half.
The levels of A.a. (and other filamentous fungi and yeasts) spore inoculum on leaves and fruits were not affected by the irrigation neither the incipient infections by A.a. on pistachio leaves.
Disease differences can be explained by differences in atmospheric parameters associated with the two irrigation systems.
BDI had somewhat lower (not statistically significant) gross yields but significantly more shell splitting.
This resulted in higher yield of marketable product (edible split nuts). In both irrigation systems, higher fruit load on shoots predisposed leaves to infection by A.a.
This work strongly suggests that control of A.a. late blight in FI pistachio orchards can be successfully accomplished by converting to BDI.
This disease affects both leaves and nuts.
Lower marketable yields due to reduced shell splitting and shell staining are the usual consequences of the disease.
This problem is most severe in flood irrigated (FI) orchards with infiltration problems and no chemical control method is currently available.
We theorized that changing orchard atmospheric conditions by reducing surface wetting could lessen A.a. damage.
The effects of buried drip (BDI) and FI on A.a. of pistachio were compared in a 32 ha mature pistachio orchard ("Kerman" on P. Integerrima) for two seasons.
BDI resulted in shorter periods of dew formation per day, lower relative humidities, and higher temperatures.
This, in turn, reduced the incidence and severity of infected leaves by A.a.
For instance, about 10 and 55% of the leaves in the BDI and FI, respectively, were infected at harvest.
Furthermore, BDI reduced the incidence of A.a. infected fruit by half.
The levels of A.a. (and other filamentous fungi and yeasts) spore inoculum on leaves and fruits were not affected by the irrigation neither the incipient infections by A.a. on pistachio leaves.
Disease differences can be explained by differences in atmospheric parameters associated with the two irrigation systems.
BDI had somewhat lower (not statistically significant) gross yields but significantly more shell splitting.
This resulted in higher yield of marketable product (edible split nuts). In both irrigation systems, higher fruit load on shoots predisposed leaves to infection by A.a.
This work strongly suggests that control of A.a. late blight in FI pistachio orchards can be successfully accomplished by converting to BDI.
Authors
D.A. Goldhamer, T.J. Michailides, D.P. Morgan
Keywords
Alternaria alternata, P. Integerrima, plant disease, subsurface, water conservation
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