Agriculture: Caneberries Pest Management Guidelines

Yellow Rust

  • Phragmidium rubi-idaei
  • Symptoms and Signs

    Of the major caneberry crops, yellow rust infects only red raspberry and is not a systemic pathogen, meaning the pathogen does not spread internally through the plant. In spring, yellowish orange pustules (aecia) form on the tops of raspberry leaves close to the ground. Early season observation of aecia on the tops of leaves is a general way to distinguish this rust from late leaf rust, which also infects red raspberry.

    Severely affected leaves can dry out and die. Later in June and July, orange to yellow pustules (uredinia) appear on the undersides of leaves; these structures later darken as black teliospores develop from the middle of July to fall. The yellow rust fungus overwinters as teliospores on the bark of remaining floricanes (fruiting canes). Such canes are the sources of inoculum that affect emerging leaves and primocanes (vegetative canes) the following spring.

    Management

    If possible and horticulturally sensible, complete removal of floricane and first flush of primocane is useful in controlling this disease, because it removes most sources of inoculum. Any method of pruning that improves air circulation is helpful in reducing yellow rust, as this allows leaves, flowers, and fruit to dry more quickly, subsequently reducing plant susceptibility. The dry conditions in a macrotunnel greatly limit the infestation of yellow rust, provided the tunnels are constructed before ideal conditions for infestation begin. In the Monterey Bay area, this generally means mid- to late July.

    Organically Acceptable Methods

    Cultivating to bury old crop debris, removal of fruiting canes after harvest, and sprays of lime sulfur or some fixed copper products are acceptable methods in an organically certified crop.

    Treatment Decisions

    Treatment for all occurrences of yellow rust are not necessary because it has been shown that light-to-moderate infections of yellow rust do not affect raspberry plant productivity. Fungicide treatments should be made with an eye to preventing large outbreaks, rather than eliminating the disease. Thus, low levels of disease late in season probably do not merit treatment, while it might be recommended to apply fungicide if signs of yellow rust are seen early in the season, for example in June.

    Common name Amount per acre REI‡ PHI‡
    (Example trade name) (hours) (days)
     
    Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used.
     
    DELAYED DORMANT
    A. FIXED COPPERS# Label rates 24 0
    MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M1)
    COMMENTS: For organically certified produce, check with your certifier for acceptable copper formulations.
     
    FIRST BLOOM
    A. FIXED COPPERS# Label rates 24 0
    MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M1)
    COMMENTS: For organically certified produce, check with your certifier for acceptable copper formulations.
     
    B. PYRACLOSTROBIN+BOSCALID
    (Pristine) 18.5–23 oz 12 0
    MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Succinate dehydrogenase inhibitor (7)
     
    C. PYRACLOSTROBIN
    (Cabrio EG) 14 oz 12 0
    MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
     
    D. MYCLOBUTANIL
    (Rally 40WSP) 1.25–1.5 oz 24 0
    MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
    COMMENTS: Initiate applications as early as budbreak and continue at 10- to 14-day intervals. Shorter intervals may be used under heavy disease pressure. Do not apply more than 10 oz/acre per season.
    # Acceptable for use on organically grown produce.
    Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) 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.
    1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. 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 a fungicide with a different mode of action Group number.
    Text Updated: 12/09
    Treatment Table Updated: 06/15