HomeBlueberriesBlueberries: Canes exhibit extremely abnormal or stunted growth

Blueberries: Canes exhibit extremely abnormal or stunted growth

Leaves may be deformed.

Causes include

 Herbicide injury

Herbicide injury by Roundup herbicide may cause abnormal or stunted growth. See also Leaf injury caused by herbicides. More herbicide damage information

 

A blueberry bush with several healthy branches and several bare branches with very small, yellow-pink leaves.
Glyphosate injury. This bush was sprayed with glyphosate in June 2023 and was photographed a year later in June 2024.
Deformed blueberry leaves with pronounced lobing and curled edges.
Roundup (glyphosate) herbicide injury.

Witches’ broom

The rust fungus Pucciniastrum goeppertianum causes unusual growth called witches’ broom. The alternate host for this fungus is white fir.

Blueberry plant with broomlike, vertical cluster of thin twigs.

Cut-off blueberry stem. Main stem is S-shaped and has many thin, vertical branches all pointing in the same direction.

 

Blueberry stem gall wasp

Blueberry stem gall wasp (Hemadas nubilipennis) cause swellings (galls) on canes at egg deposition.

Dormant blueberry bush with several swellings roughly the size and shape of unshelled peanuts. Swellings are maroon in color and are located on twigs off of the main branch at varying heights.

Swellings first appear greenish to red in color. Older galls appear gray and corky and often have exit holes.

Blueberry stem with three lumpy, egg-shaped galls. Two galls are bright red and shiny. One gall is lumpy, dull gray, and has multiple pin-sized holes.
Old and new galls from blueberry stem gall wasp. Older galls have exit holes and grayish color.

Larvae overwinter in galls then emerge as adults in spring.

Cross-section of corky gall showing multiple internal chambers. One chamber has a cream-colored sphere inside of it.
Cross-section of gall with overwintering larva.
Close-up of a curled, translucent larva inside of a frass-lined tunnel. Larva has no discernible limbs or features.
Cynipic gall wasp larva.
Blueberry branch with cluster of blossoms, leaves, and large dark corky mass situated above blossom cluster. A black wasp the size of a pinhead is perched atop the black gall.
Blueberry stem gall wasp perches atop a gall.

Crown gall

Infection by the crown gall, bacterium Agrobacterium tumefaciens, results in abnormal swelling of canes and stems.

Blueberry branch with large, brown, fibrous swelling along entire length.
Large gall on blueberry cane. Photo courtesy W. Bertram.

 

Blueberry stem with bark scraped off to show multiple small brown bumps developing underneath bark.
Smaller galls erupting from under bark. Photo courtesy W. Bertram.

Blueberry Stunt

Severe stunting could be caused by a mycoplasma called blueberry stunt. Leaves are small and tend to be cupped downwards.

Blueberry bush with wilted and cupped leaves. Leaves are dark green and bush otherwise appears healthy.

Single young blueberry twig with downward-cupped leaves. Leaves appear smaller in overall size than usual.

The organism is transmitted by the sharp-nosed leafhopper (Scaphytopius magdalensis).

Blueberry leaf with small, brown, mottled insect with trapezoid body shape. Insect viewed from above.
Adult sharp nosed leafhopper on blueberry leaf.

Leafhoppers must be managed to minimize the spread of stunt.

White, soft-bodied insect viewed from above. Leafhopper has red eyes on side of head, sharp triangular abdomen and triangular head. A black vest-like pattern is on the thorax.
First of 5 instars of sharp-nosed leafhopper.