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CRANBERRIES
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Cranberry Tipworm
Order: Diptera || Family: Cecidomyiidae (gall midges)
Dasineura oxycoccana (Johnson)
LIFE CYCLE IN MAINE
Adults: early to mid-May - Sept.
Larvae: mid-May - end of August
The larvae of cranberry tipworm, as the name implies, feed on the tips of cranberry uprights and runners (new growth only). They are equipped with scraping mouth parts that, upon feeding, results in a characteristic cupping and whitening of the terminal leaves. Heavy feeding leads to the death of the growing point, and the blackened result may sometimes be confused with either frost damage or heat stress. The plant responds to the loss of the terminal growing point by rebranching from lateral buds in an attempt to compensate for the damage.  During short growing seasons, such as in Maine and Wisconsin, much of the regrowth produces vegetative rather than fruiting buds, giving rise to a potentially significant reduction in the following year’s crop.
 
General Tipworm Facts:
  • Females lay eggs near base of terminal leaves (need a dissecting scope to see them).
  • Larvae feed (rasp) on new leaves.
  • As many as 5 generations of larvae per season.
  • Injured leaves lose their color, become cupped, and eventually die, along with the growing point.
  • Early-season injury: lateral branching (but often give rise to vegetative buds rather than flower buds).
  • Late-season injury: probably non-flowering uprights the following year (Maine situation differs here with that in Massachusetts--which has a slightly longer growing season--allowing cranberry tips more recovery time before the onset of dormancy).
  • Last-generation of larvae overwinter on the bed (within the trash layer) as pupae in cocoons.
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Management:
  • B.t., Confirm, or Intrepid will not work on this insect whatsoever since it is a fly larva and not a caterpillar! The B.t. bacterium--at least the kurstaki strain used in most pest control programs--is simply not toxic to the digestive system of flies (larva or adults) like it is to that of Lepidopteran insects (i.e., caterpillars).
  • No researched Action Threshold (AT), but suggested AT in Maine from 2003-2006 (for anyone expecting no more than 40 cents per pound for their berries) is 60% infestation of tips by eggs and/or larvae (or 60% of tips already damaged). (sample size = 40 to 50 tips)
  • Traditional strategy was to treat (if needed) during the peak of egg-hatch, usually mid to late May in Maine (population is very synchronized at that time). The current thinking has changed somewhat, to targeting the fly stage, before egg-laying can take place, but timing for the fly stage is a challenge because the flies live for only 4 to 5 days.
  • Follow-up with examination of at least 25 tips 2 to 3 days later and, if spraying again is deemed appropriate, make an application as soon as possible.
  • Sanding--especially heavy sanding--reduces populations, particularly early spring levels; However, after just a few weeks, levels can increase again.
  • Avoid late-season fertilizer applications! (because tipworm larvae prefer actively-growing tissue) 
 
Dissecting Microscope Images
A pair of cranberry tipworm eggsA pair of cranberry tipworm eggs
Egg Stage
(There are 2 eggs close together in each of the above images.  Notice the orange dot, which
is thought to give rise to the mouthpart of the larva.)

Clear stage of a cranberry tipworm larva
1st Larval Stage (clear)
(larva is on the tip of a forcep)

White larval stage of a cranberry tipworm larvaTipworm larvae inside a small vial
2nd Larval Stage (white)
(LEFT: single larva on the tip of a forcep; RIGHT: a few dozen larvae inside a small, 10 ml vial)
(Larvae inside vial collected 7/15/1996 from Washington County, Maine)

last instar cranberry tipworm larvaFinal growth stage of a tipworm larva
3rd and final Larval Stage (orange)
(The larva is difficult to control at this stage.)

Cocoon stage of a tipworm larva2 cranberry tipworm cocoons
Cocoon Stage
(LEFT: 2 cocoons)
(RIGHT: One cocoon's casing has been partially torn away, exposing the orange pupa inside.)

A female cranberry tipworm flyadult female tipworm fly
Adult Stage (2 females)
(Females are orange; Males are black)
If you have comments or questions about this page,
contact Charles Armstrong at: charlesa@umext.maine.edu
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These pages are currently being maintained by the Pest Management Office, University of Maine Cooperative Extension. Page Last Modified: 05/15/08