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How to Manage Pests
UC Pest Management Guidelines
Peach
Brown Rot Blossom and Twig Blight
Pathogens: Monilinia fructicola, occasionally Monilinia laxa
(Reviewed 3/06,
updated 3/06)
In this Guideline:
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SYMPTOMS
Young blossom spurs and
associated leaves collapse to form shoot blight. Gum exudes at
base of infected flowers. Cankers on blighted twigs have tan centers with dark
margins. Gray brown spore masses form on diseased flower parts and twig cankers under high humidity.
Monilinia fructicola overwinters on mummified fruit that either fall to the ground in late fall or early winter, or remain in the
trees. In spring, apothecia form on mummies that are on the ground; these apothecia release ascospores at
the same time as the trees bloom. Ascospores serve as primary inoculum for brown rot in
many orchards. Mummies in the trees as well as those on the ground may also
produce conidia, which may serve as the primary source of inoculum in some
years. Twig lesions apparently do not produce spores.
Although all flower parts except the sepals are susceptible to
infection by M. fructicola, only infection
of the stamens leads to the development of blossom and twig blight.
Bloom sprays to reduce blossom and twig blight help minimize loss to
ripe fruit rot at
harvest. Removal of remaining fruit from trees soon after harvest will help
reduce inoculum the following spring.
Take fruit samples every other week after color break (see
PREHARVEST FRUIT SAMPLES) to detect any developing problems in the orchard and
a fruit damage sample at harvest to assess the effectiveness of the current
year's IPM program and to determine the needs of next year's program (see FRUIT EVALUATION AT HARVEST).
Chemical Control
Make a treatment at 20 to 40% bloom and
again at 80 to 100% bloom if heavy rainfall or other conditions are occurring
that result in high susceptibility to infection. Aerial applications are
generally not as effective as properly applied ground sprays but may be
necessary when the orchard floor is wet. To help prevent development of
resistance to fungicides, be sure to rotate chemicals that have different mode
of action group numbers.
| Common name |
|
P.H.I.+ |
| (trade name) |
Amount to Use |
(days) |
|
| The following materials are
listed in order of usefulness in an IPM program, taking into account
efficacy. When choosing a pesticide, also consider information relating to
environmental impact.
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| A. |
PROPICONAZOLE |
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(Bumper, Orbit) |
4 oz/acre |
0 |
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MODE OF ACTION: A DMI (Group 3)1
triazole fungicide.
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COMMENTS: A sterol inhibitor fungicide. |
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| B. |
TEBUCONAZOLE |
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(Elite) 45WP |
4–8 oz/acre |
0 |
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MODE
OF ACTION: A DMI (Group 3)1 triazole fungicide.
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COMMENTS: A sterol inhibitor fungicide. Do not apply more than 3 lb/acre/season. |
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| C. |
FENBUCONAZOLE |
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(Indar) 75WSP |
2 oz/acre |
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MODE OF ACTION: A DMI (Group 3)1
triazole fungicide.
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COMMENTS: A sterol inhibitor fungicide. Do not apply more than 1 lb/acre/season. |
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| D. |
IPRODIONE |
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(Rovral) 4 |
1–2 pt/acre |
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MODE OF ACTION: A dicarboximide (Group
2)1 fungicide.
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COMMENTS: Addition of a narrow range
oil (superior, supreme) at 1–2% increases the effectiveness of this material. May not be used after petal fall. |
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| E. |
PYRACLOSTROBIN/BOSCALID |
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(Pristine) |
10.5–14.5 oz/acre |
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MODE OF ACTION: A Qol (Group 11)1 and carboxamide
(Group 7)1 fungicide.
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COMMENTS: To reduce the potential for
resistance, do not make more than 5 applications of this or other Group 11 or
7 fungicides per season. Do not make more than 2 sequential applications of this product. |
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| F. |
THIOPHANATE METHYL |
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(Topsin-M) 70WP |
8 oz/100 gal water |
1 |
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MODE OF ACTION: A MBC (Group 1)1
thiophanate fungicide.
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COMMENTS: Strains of Monilinia
fructicola resistant to thiophanate
methyl are common, especially in the Sacramento and northern San Joaquin
Valleys. If resistance has occurred in your orchard, do not use this
fungicide; otherwise, one application at early bloom is usually sufficient.
If brown rot is severe, or an extended bloom period is accompanied by
rainfall, make a second application using a fungicide with a different group number. |
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| G. |
CYPRODINIL |
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(Vangard) WG |
5 oz/acre |
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MODE OF ACTION: An AP (Group 9)1 fungicide. |
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COMMENTS: Do not apply more than 10 oz/acre/year. |
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| H. |
PYRIMETHANIL |
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(Scala) SC |
18 fl oz |
7 |
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MODE OF ACTION: An AP (Group 9)1 fungicide. |
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| I. |
FENHEXAMID |
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(Elevate) 50 WDG |
1–1.5 lb/acre |
0 |
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MODE OF ACTION: A hydroxyanilide (Group 17) 1
fungicide.
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COMMENTS: Avoid making more than 2 consecutive applications of this material. |
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| J. |
MYCLOBUTANIL |
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(Rally) 40W |
2.5–6 oz/acre |
0 |
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MODE OF ACTION: A DMI (Group 3)1
triazole fungicide.
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COMMENTS: Do not apply more than 3.28 lb/acre/season. |
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| L. |
AZOXYSTROBIN |
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(Abound) |
12.3–15.4 fl oz/acre |
0 |
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MODE OF ACTION: A Qol (Group 11)1 fungicide. |
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COMMENTS: Do not apply more than two
applications before alternating with a fungicide that has a different mode of action. |
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| M. |
CHLOROTHALONIL |
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(Echo 720) |
3.125–4.125 pt/acre |
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(Bravo Ultrex DF) |
2.8-3.8 lb/acre |
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(Bravo Weather Stik) |
3.125–4.125 pt/acre |
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MODE OF ACTION: A multi-site contact (Group M5)1
chloronitrile fungicide.
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COMMENTS: Do not use with or closely following oil sprays. May not be used after jacket split. |
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| N. |
CAPTAN 50WP |
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(various products) |
2 lb/100 gal water (dilute spray) |
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MODE OF ACTION: A multi-site contact (Group M4)1
phthalimide fungicide.
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COMMENTS: Do not apply in combination with, immediately before, or closely following oil sprays. |
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More information on peach fungicides
UC IPM Pest Management Guidelines: Peach
UC ANR Publication 3454
Diseases
W. D. Gubler, Plant
Pathology, UC Davis
J. E. Adaskaveg, Plant Pathology, UC Riverside
J. K. Hasey, UC Cooperative Extension, Sutter/Yuba counties
Acknowledgment for contributions to the diseases section:
B. L. Teviotdale, Kearney Agricultural Center, Parlier
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