Ciclo de vida e índicedel mildiú polvoriento

(Erysiphe necator,Uncinula necator)

Lynn Wunderlich, Farm AdvisorUniversity of California Cooperative Extension-

Central Sierra

Photos:UCANR,UCIPM and U.C. Regents

Powdery mildew has 2 spore types:

Chasmothecia are spore “sacs”. Each sac contains many ascospores. The sac carries the disease over winter-from one

year to the next.

Conidia are asexual spores in a chain. Produce disease during the

growing season.L.R. Wunderlich, University of California Cooperative Extension

In vineyards with high disease incidence, the powdery mildew life cycle for the next year begins in the late summer/fall of the current year-when the chasmothecia form in infected berries, leaves and shoots.

L.R. Wunderlich, University of California Cooperative Extension

In winter, rain washes the chasmothecia into the vine trunk and cordon arm bark.

The chasmothecia protects the spores inside and overwinters the disease in this way.

L.R. Wunderlich, University of California Cooperative Extension

10°-27° COptimal: 20°-24°C

In Spring, chasmothecia release the ascospores with ~ 10 mm. moisture (rain, fog, dew, irrigation) and optimal temperatures.

L.R. Wunderlich, University of California Cooperative Extension

GREEN tissue is required for infection by ascospores to occur. This is called “primary” or “initial” infection. L.R. Wunderlich, University of California Cooperative Extension

L.R. Wunderlich, University of California Cooperative Extension

L.R. Wunderlich, University of California Cooperative Extension

Bud Perennation. The fungus can also overwinter is in buds that were covered with mildew the previous year. The shoot emerges with powdery mildew mycelium growth on it-called a “flag shoot”. These shoots then produce conidia. Can occur in highly susceptible varieties like Carignane.

L.R. Wunderlich, University of California Cooperative Extension

After initial infection by ascospores, powdery mildew mycelium grows and produces conidia. The rest of the powdery mildew life cycle is driven by conidia infections during the growing season. Mildew growth is dependent on optimal temperature of 21°-30°C.

Optimal relative humidity is 65%. Rain is not needed and can even wash conidia off of the leaves.

L.R. Wunderlich, University of California Cooperative Extension

Across a landscape, powdery mildew infections start in blocks that had infections the previous year. Once the ascospores in that block germinate and grow mycelium-conidia are produced that can infect other blocks.

L.R. Wunderlich, University of California Cooperative Extension

6/9/2014-Untreated

L.R. Wunderlich, University of California Cooperative Extension

6/26/2014

L.R. Wunderlich, University of California Cooperative Extension

L.R. Wunderlich, University of California Cooperative Extension

Berries are no longer susceptible at 8% sugar. Spores are produced until 15% sugar.

L.R. Wunderlich, University of California Cooperative Extension

L.R. Wunderlich, University of California Cooperative Extension

The powdery mildew index uses canopy temperature to predict risk of infection. Goal: Minimize unnecessary mildew sprays while maintaining quality (no disease).

L.R. Wunderlich, University of California Cooperative Extension

L.R. Wunderlich, University of California Cooperative Extension

L.R. Wunderlich, University of California Cooperative Extension

How the mildew index accumulates points forpredicting conidial infections.

Based on canopy temperature. Scale is 0-100.

• 6 or more continuous hours between 21°C-30°C: Add 20 points

• Less than 6 continuous hours between 21°C-30°C:Subtract 10 points

• If 35°C or higher for 15 minutes or more:Subtract 10 points

L.R. Wunderlich, University of California Cooperative Extension

In spring, the mildew index starts when

there are more than 3 consecutive days with 6 or more hours

of temperatures from 21° to 30°C

L.R. Wunderlich, University of California Cooperative Extension

Budbreak

L.R. Wunderlich, University of California Cooperative Extension

L.R. Wunderlich, University of California Cooperative Extension

DISEASE PRESSURE RATINGS USING THE POWDERY MILDEW INDEX

Index Disease pressure Pathogen status

0-30 low present

30-50 intermediate reproduces every 15 days

60 or above high reproduces every 5 days

L.R. Wunderlich, University of California Cooperative Extension

Suggested spray schedule

Index Disease pressure

Biologicals and SARs(i.e. Serenade)

SulfurSterol-inhibitors(i.e. Rally)

Strobilurins(i.e. Pristine)

0-30 low 7- to 14-day interval

14- to 21-day interval

21-days or label interval

21-day or label interval

30-50 intermediate 7-day interval 10- to 17-day interval

21-day interval

21-day interval

60 or above high use not

recommended 7-day interval

10- to 14-day interval

14-day interval

L.R. Wunderlich, University of California Cooperative Extension

PMI 2015-2016: Lava Cap Vineyard

L.R. Wunderlich, University of California Cooperative Extension

L.R. Wunderlich, University of California Cooperative Extension

L.R. Wunderlich, University of California Cooperative Extension

3 ways the PMI can help save a spray* ($ $):• First spray of the season

delayed

• Spray intervals lengthened (so fewer sprays per season)

• High temperature periods drop PMI

*“clean” blocks only, not susceptible varieties L.R. Wunderlich, University of California Cooperative Extension

Thankyou!

L.R. Wunderlich, University of California Cooperative Extension

L.R. Wunderlich, University of California Cooperative Extension

This presentation was created by Lynn R. Wunderlich, Farm Advisor, Central Sierra University of California-Cooperative Extension and presented at the:

Primer Seminario Internacional Vitivinícola del Sur de Chile “Manejo Integral del Viñedo para aumentar productividad y calidad” Centro de Extensión Vitivinícola del Sur Día: Jueves 16 de Noviembre de 2017 Lugar: Auditorium INIA Quilamapu, Vicente Méndez 515, Chillán.

Lynn can be contacted atlrwunderlich@ucanr.edu