Maine Cranberry Management Calendar

CRANBERRIES

Maine Cranberry Management Calendar

Green text is for horticultural events and management activities. Red text is for insect pest events and management activities. Blue text is for disease events and management activities. Black text is for all other crop management activities
Yellow highlighted boxes are for those activities considered to be of very high priority.

Start Dates and/or Plant Stages	Biological Events and Management Activities

Mid to Late April	Pre-emergence herbicides need to be applied before cranberry vines break dormancy. For a list of herbicides, and individual target weeds, check the weeds portion of the Maine Cranberry Pest Management Guide.
~Late April	Late Water (LW) flood. Do not apply the flood if the buds have broken dormancy, or if the winter has been severely cold and long, oxygen deficiency conditions are suspected, or if the bed has been sanded since the preceding fall. Provides very good control of fruit rot fungi and boosts keeping quality; Kills overwintering Cranberry Fruitworm and may eliminate the need for sprays for this insect during the LW year (Expect 90% or more Cranberry Fruitworm control if flood is held for 4 weeks, 40-50% range if shorter duration); Virtually wipes out Southern Red Mite infestations; May suppress False Armyworm and Gypsy Moth larval populations; Can delay the development of weeds (suppresses growth of some perennials, most notably brambles) (LW does not control dodder);
Weeds just starting to emerge (best if <5" tall, yet growing actively) (~From May to 45 days before harvest or flooding, and not during bloom)	Callisto is reportedly an extremely good choice for weed control, having both pre-emergence activity as well as post-emergence activity (especially when weeds are <5" tall), and you are encouraged to wait for that stage (if you apply 'too' early, some weeds with vast root systems--such as cinquefoil--can quickly recover. So, for cinquefoil, wait until the first flush of new growth has taken place. The maximum application rate is 8 oz/acre/application; no more than two apps. per season, and split apps. need to be at least 14 days apart. Callisto is effective against a large number of different weeds (will control most all annual broadleaf weeds if under 5" tall), but plan on several years of treatment in order to achieve permanent control of many perennial weeds, especially yellow loosestrife/swamp candles. Birdsfoot trefoil and other Lotus members are very sensitive to Callisto (but more difficult to control if they are completely covering over the cranberry canopy). Cranberry vines are highly tolerant of Callisto - they can readily metabolize its active ingredient (mesotrione).
May (after terminal bud has broken dormancy & begun to swell or grow)	The approximate window for spraying for UPRIGHT DIEBACK control is April 30 - May 20. For Washington County growers, the target window is likely a bit later (May 6 - 26). But, exact timing depends on whether the variety is early or late-season. Remember, too, that if a chlorothalonil application is used at this time, that leaves only two more available that you can use for fruit rot control. For a list of available fungicides you can use, and details about the disease, consult the Maine Cranberry Pest Management Guide. NOTE:Bravo does not control upright dieback if applied later than early bloom—by this time the fungus has apparently invaded shoots and is out of reach of the material. Fungicides will not cure upright dieback but will prevent the spread of the infection.
~May 14 - May 31 (vegetative buds elongated 1/2" and flowering buds at bud break stage)	Cranberry tip worm begins! Overwintering pupae will be hatching out into flies (the length of this period is a bit uncertain). Individual flies only live for about 3 days (5 at most), so right out of the gate they are busy mating and laying eggs on the terminal leaves of uprights with buds that have begun to elongate. The more dormant the upright, the less likely its chances of being chosen for egg deposition by the female tipworm fly. Conventional wisdom is to treat at peak of egg hatch, though some growers are targeting the flies, hoping to kill them before they can lay their eggs. The window for either of these two spray strategies is extremely narrow. Preliminary Degree day model (From 2007 work; repeating in 2008): Using a base of 45F, an estimated 510 degree days are needed for emergence; Using a base of 50F, an estimated 344 degree days are needed. Sweepnet First Dates (for flies): 5/14/07 in Mt. Vernon; 5/28/07 in Troy.
~May 20 - early June (tip elongation)	False Armyworm larvae begin (If no Late Water flood was used). These cutworms have been consistently found in significant numbers on Maine cranberry beds annually. The larvae feed on leaves, stems and buds (basically consume entire uprights), and get quite big when mature (2” long), at which point they feeds almost exclusively at night. Sweepnet First Dates: 6/6/97, 5/28/98, 5/28/99, 5/24/00, 5/31/01, 5/13/02, 5/24/05.
	1st-generation Black-headed fireworm larvae begin. Spend some time visually scanning for upright tips with terminal leaves that have been webbed tightly together! Break off any tip of that sort, and carefully tease apart the terminal leaves. If a small larva suddenly squirms out, wriggling backwards and possibly right across your hand and down to the ground (often attached to a strand of silk--very much like Spider Man)...and if this happens before you've even blinked, then you've probably encountered a fireworm larva. You should then sweep to see if you pick up any in your net. They do not get picked up in sweeps very easily, so if you average even ONE larva per 25 sweeps, you may well be justified in taking action (depending on your history with this pest, your expected crop value, etc.). View the Maine Cranberry Pest Management Guide for the most current recommended Action Threshold (AT) to consider using (traditional AT is 1), and for a list of control materials (Avaunt is a new choice as of the 2008 season). Infestations of 2nd-generation larvae are far more dangerous, because their numbers are much higher, especially--of course--if any 1st-generation populations are left uncontrolled. Infestations of both generations are usually patchy, at least at first, and larvae tend to be more numerous along edges. Spot-treatment is desirable in such cases. Sweepnet First Dates (1st-gen larvae): 6/12/06, 5/25/07.
1st week of June, ± 1 week	Gypsy Moth caterpillars begin to show up on beds, mostly blown in from forested areas though they can also overwinter right on the beds. Their numbers can be fairly numerous in some years. Add the number of these larvae to any cutworms and humped green fruitworms found when using a thresholds table. This insect is cyclic and in the past has undergone major outbreaks every 9 to 10 years in the northeastern U.S. and Canada. The larva is one of North America’s most devastating forest pests (especially fond of oak and aspen). It has no problem eating cranberry foliage as well. Check for patchy infestations that can be spot-treated, e.g. along bed edges facing trees that might be infested. Check any previously infested areas. Early detection is key: larvae consume terminal buds and any new growth that has begun. To learn even more about gypsy moth, visit http://www.umassgreeninfo.org/fact_sheets/defoliators/gypsey_moth.html Sweepnet First Dates: 5/29/00, 5/20/01, 6/13/02, 6/12/06, 6/6/07.
DISCLAIMER: Pesticide registration status is subject to change and varies from state to state; therefore the author and the University of Maine Cooperative Extension cannot assume liability for recommendations. It is the responsibility of the applicator to verify the registration status of any pesticide BEFORE applying it. THE LABEL IS THE LAW: ALWAYS READ AND FOLLOW THE LABEL WHEN APPLYING PESTICIDES. Use of product names does not imply endorsement.

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