How to Manage Pests

UC Pest Management Guidelines

SYMPTOMS

Powdery mildew is marked by superficial, white, weblike growth on leaves, shoots, or fruit.

COMMENTS ON THE DISEASE

The fungus overwinters in buds on twigs and as chasmothecia, which are spore-containing structures, on the bark of twigs and branches. Secondary spores produced in spring spread the fungus to new growth. Infections can be severe in commercial orchards during years of low rainfall, high humidity, and warm temperatures (70° to 80°F). The disease is particularly severe on new growth, such as shoots of inner scaffolds, and can infect fruit as well, causing direct crop loss. In warm, humid, coastal areas, powdery mildew can also be severe after harvest.

MANAGEMENT

To protect fruit, spray soon after petal fall and 2 to 3 weeks later if needed. Treat immediately if mildew is found on leaves or shoots of inner scaffolds or water sprouts. Do not use the same fungicide or fungicides with similar chemistry more than twice in one year to reduce the potential for the development of resistance by the pathogen to the fungicide. In orchards with a history of mildew, select fungicides that are active against brown rot and Botrytis, as well as powdery mildew during bloom and immediately before harvest, being careful to note the preharvest interval.

Common name		Amount/Acre	R.E.I.+	P.H.I.+
(trade name)			(hours)	(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. Not all registered pesticides are listed. Always read label of product being used.
A.	QUINOXYFEN
	(Quintec)	7 fl oz	12	7
	MODE OF ACTION GROUP NAME (NUMBER1): Quinoline (13)
	COMMENTS: Treat early; this product is a protectant so do not use if disease symptoms are present. Apply at full bloom and 2 weeks after petal fall. If additional treatments are necessary, rotate with a fungicide that has a different Group number. Do not apply more than 35 fl oz/acre/year or make more than 5 applications/year.
B.	TRIFLUMIZOLE
	(Procure) 50W	8-16 oz	12	1
	MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
C.	PYRACLOSTROBIN/BOSCALID
	(Pristine)	10.5–14.5 oz	12	0
	MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Carboxamide (7)
D.	PYRACLOSTROBIN
	(Cabrio) EG	9.5 oz	12	0
	MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
E.	TRIFLOXYSTROBIN
	(Gem) 500SC	1.9–3.8 oz	12	1
	MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
F.	MYCLOBUTANIL
	(Rally) 40W	2.5–6 oz	24	0
	MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
	COMMENTS: Do not apply more than 3.2 lb product/acre/season. More effective when applied as a concentrate (80-100 gal/acre) than as a dilute spray.
G.	FENARIMOL
	(Rubigan) EC	6–12 oz/200 gal water	12	0
	MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
	COMMENTS: Apply a treatment at late bloom to petal fall and repeat at 14–21 day intervals as required for control until harvest. Do not apply more than 36 oz before harvest.
H.	PROPICONAZOLE
	(Bumper, Orbit) 3.6EC	2-4 fl oz	see comments	0
	MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
	COMMENTS: Apply at popcorn. REI os 24 hours for Bumper and for Orbit, 12 hours. More effective when applied as a concentrate (80-100 gal/acre) rather than a dilute spray. Do not apply more than 8 fl oz/acre/crop.
I.	TEBUCONAZOLE
	(Elite, Orius, etc.) 45WP	4-8 oz	12	0
	MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
	COMMENTS: More effective when applied as a concentrate (80-100 gal/acre) rather than a dilute spray.
J.	FENBUCONAZOLE
	(Indar) 70WSP	Label rates	12	0
	MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
K.	AZOXYSTROBIN
	(Abound)	11–15.4 fl oz	4	0
	MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
	COMMENTS: Do not apply more than three sequential sprays of this product before alternating with a fungicide with a different Group number.
L.	THIOPHANATE METHYL
	(Topsin-M) 70WP	0.5 lb/100 gal water up to 1.5 lb/acre	12	1
	MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
	COMMENTS: Use only once a year. Do not use in orchards where resistance has been observed. Use only in combination or in an alternating application program with a fungicide with a different Group number. Resistant populations to benzimidazole fungicides may result in low performance or a failed fungicide treatment.
M.	WETTABLE SULFUR#
	(80-92% Sulfur)	10–20 lb	24	0
	MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M2)
	COMMENTS: Do not enter treated areas for 24 hours unless protective product clothing is worn. Do not apply within 3 weeks of an oil application. May cause outbreaks of pest mites; at temperatures above 85°F, may cause phytotoxicity.
N.	POTASSIUM BICARBONATE
	(Kaligreen)	2.5–3 lb	4	1
	MODE OF ACTION GROUP NAME (NUMBER1): Not classified
O.	LIQUID LIME SULFUR#	2–3 gal/100 gal dilute	48	0
	MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M2)
	COMMENTS: Lime sulfur is incompatible with most other pesticides. Check before use. Use in delayed dormant season only, not during the growing season.
+	Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
#	Acceptable for use on organically grown produce.
1	Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to fungicide with a different mode of action Group number.

PUBLICATION

UC IPM Pest Management Guidelines: Cherry
UC ANR Publication 3440
Diseases
J. E. Adaskaveg, Plant Pathology, UC Riverside
J. L. Caprile, UC Cooperative Extension, Contra Costa County
Acknowledgment for contributions to Diseases:
W. D. Gubler, Plant Pathology, UC Davis
B. L. Teviotdale, Kearney Agricultural Center, Parlier

Top of page