Articles
Two practical techniques to determining presence/ absence and predicted levels of Botryosphaeria panicle and shoot blight of pistachio during the dormant season and in the spring
Article number
1406_57
Pages
403 – 410
Language
English
Abstract
Botryosphaeria (Bot) panicle and shoot blight of pistachio is caused by 10 different species that belong to the Botryosphaeriaceae family.
If left unmanaged, Bot can be extremely destructive.
Growers currently have many fungicides registered for controlling Bot panicle and shoot blight.
In recent years the lack of spring rains and the long drought periods have created an environment of less Bot blight pressure and fungicide application should be more judicious to address environmental concerns about the impact of synthetic fungicides applied in orchards.
We developed two assays that identify Botryosphaeria fungi infesting pistachio buds which lead to latent infections on immature fruit.
The first assay called ‘bud monitoring’ (BUDMON) consists of collecting randomly 100 dormant buds in late February and March from a pistachio orchard up to 20 acres, surface sterilizing them in a 10% household bleach solution, and plating them aseptically in Petri dishes (10 buds per dish, 10 dishes per orchard). The dishes are incubated at 27°C (81°F) for 4-6 days after which Botryosphaeria colonies originating from the buds are recorded as % of total buds.
The second assay, called ‘Overnight Freezing Incubation Technique’ (ONFIT), involves a collection of 100 random immature pistachio fruit.
These fruits are surfaced sterilized as above and placed in plastic containers, 200 mL water is added in each container, and the containers are placed in a freezer (-15°C, 5°F) overnight (at least for 12 h). Following freezing, the containers are placed on a bench at room temperature for 5-6 days after which fruit covered with Botryosphaeria fungi are recorded.
The results of these assays correlate with the disease levels that develop at harvest in the orchards.
If left unmanaged, Bot can be extremely destructive.
Growers currently have many fungicides registered for controlling Bot panicle and shoot blight.
In recent years the lack of spring rains and the long drought periods have created an environment of less Bot blight pressure and fungicide application should be more judicious to address environmental concerns about the impact of synthetic fungicides applied in orchards.
We developed two assays that identify Botryosphaeria fungi infesting pistachio buds which lead to latent infections on immature fruit.
The first assay called ‘bud monitoring’ (BUDMON) consists of collecting randomly 100 dormant buds in late February and March from a pistachio orchard up to 20 acres, surface sterilizing them in a 10% household bleach solution, and plating them aseptically in Petri dishes (10 buds per dish, 10 dishes per orchard). The dishes are incubated at 27°C (81°F) for 4-6 days after which Botryosphaeria colonies originating from the buds are recorded as % of total buds.
The second assay, called ‘Overnight Freezing Incubation Technique’ (ONFIT), involves a collection of 100 random immature pistachio fruit.
These fruits are surfaced sterilized as above and placed in plastic containers, 200 mL water is added in each container, and the containers are placed in a freezer (-15°C, 5°F) overnight (at least for 12 h). Following freezing, the containers are placed on a bench at room temperature for 5-6 days after which fruit covered with Botryosphaeria fungi are recorded.
The results of these assays correlate with the disease levels that develop at harvest in the orchards.
Authors
T.J. Michailides, V.M. Gabri, D.P. Morgan
Keywords
biological assay, Botryosphaeria dothidea, disease prediction, latent infection
Groups involved
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