How to Manage Pests

UC Pest Management Guidelines

Almond

Leaf Blight

Pathogen: Seimatosporium lichenicola

(Reviewed 3/09, updated 3/09)

In this Guideline:

SYMPTOMS AND SIGNS

Individual leaves on spurs or shoots wither and die in early summer. The fungus kills the petioles and the axillary buds. Leaf blades disintegrate, but diseased petioles stick on tree during winter. When the axillary bud is killed, spurs do not develop.

COMMENTS ON THE DISEASE

The fungus survives on dead petioles. Spores are spread by rain, and disease is favored by wet spring weather. Leaf blight is usually not very severe or widespread; it rarely destroys more than 20% of the leaves in one season. Repeated early death of leaves will weaken trees, however, and may contribute to loss in yield as a result of the loss of spur development.

MANAGEMENT

Treat during the period from bloom through early spring. Make the first application during early leafing, which usually occurs at full bloom to petal fall. Pink bud is too early for control.

Common name		Amount/Acre	R.E.I.+	P.H.I.+
(trade name)			(hours)	(days)
When choosing a pesticide, consider its usefulness in an IPM program by reviewing the pesticide's properties, efficacy, application timing, and information relating to resistance management, honey bees (PDF), and environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
A.	AZOXYSTROBIN
	(Abound)	11–15.4 oz	4	28
	MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
	COMMENTS: Do not apply more than 3 sequential sprays before alternating with a fungicide that has a different mode of action. Do not apply more than 4 applications of strobilurin fungicides/year or apply more than 2.88 qt/product/acre/season.
B.	TRIFLOXYSTROBIN
	(Gem)	6–8 oz	12	60–see comments
	MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
	COMMENTS: Do not apply within 60 days of harvest or after hullsplit. Do not exceed more than 3 applications of all QoIs per season to limit the potential for the development of resistance. Do not apply more than 12 oz/acre/season.
C.	MYCLOBUTANIL
	(Laredo EC)	8–12.8 fl oz	24	90
	MODE OF ACTION GROUP NAME (NUMBER1): Demethylation (sterol) inhibitor (3)
	COMMENTS: Apply in 400 gallons water/acre. Do not make more than 3 applications or apply more than 38.4 fl oz/acre/season.
D.	CAPTAN
	(various 50WP)	8 lb	4 days	See label
	MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M4)
	COMMENTS: See label for preharvest interval, which varies depending on formulation and if hulls are to be fed to livestock. Do not apply in combination with, immediately before, or closely following oil sprays.
E.	ZIRAM 76DF	8 lb	48	0
	MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M3)
	COMMENTS: Do not apply more than 32 lb/acre/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 these two intervals is the minimum time that must elapse before harvest may occur.
1	Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (For more information, see 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: Almond
UC ANR Publication 3431

Diseases

J. E. Adaskaveg, Plant Pathology, UC Riverside
W. D. Gubler, Plant Pathology, UC Davis
Roger Duncan, UC Cooperative Extension, Stanislaus County
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center, Parlier
B. A. Holtz, UC Cooperative Extension, San Joaquin County

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