blueberry stem gall wasp

(Hemadas nubilipennis)

Conservation Status
blueberry stem gall wasp
Photo by Luciearl
  IUCN Red List

not listed

 
  NatureServe

not listed

 
  Minnesota

not listed

 
           
 
Description
 
 

Blueberry stem gall wasp is a tiny, gall-forming, chalcid wasp. It occurs in the United States and southern Canada east of the Great Plains. In Minnesota it is common in the northeast quarter of the state.

Blueberry stem gall wasp forms a multi-chambered swelling (gall) on a highbush or lowbush blueberry stem. It is often found in wild blueberry populations. It has only recently become a significant pest of commercial blueberry crops.

The female lays multiple eggs in a young stem. Most egg laying, about 70%, takes place low in the stem, within leaf litter near the ground. The remaining is higher on the stem. After laying eggs, the female climbs to the stem tip and stabs it several times. This causes severe damage and often causes the stem to stop growing. Before the eggs hatch, the plant forms a soft, red swelling composed of non-vascular (parenchymatous) cells. After the eggs hatch and the larvae begin to feed, stronger, fibrous (sclerenchymatous) cells form walls around each larval chamber. By mid-summer the gall is hard, woody, darker reddish green, kidney-shaped, and ¼ to 1½ (7 to 38 mm) long. The size is determined by the number of eggs in the gall.

Most adults by far are female. They are 116to (2 to 2.5 mm) in length. The head, thorax, and abdomen are black.

The antennae are bent (elbowed) and have 10 segments. The first segment (scape) is long. The end segments are enlarged, creating a club at the tip. They are mostly orangish yellow, but the club is black.

The rear part of the body (gaster) is coarsely sculptured. On the female, the needle-like egg-laying tube (ovipositor) is short.

The forewings are long, reaching to the end of the abdomen. They are clear and lightly tinged with black. They have no closed cells. The veins reach more than halfway to the tip.

The legs are orangish yellow. On the hind legs, the third segment (femur) is not swollen, and the fourth segment (tibia) is more or less straight. The last part of each leg (tarsus), corresponding to the foot, has 5 segments.

 
     
 

Size

 
 

Total length: 116to (2 to 2.5 mm)

 
     
 

Similar Species

 
     
     
 
Habitat and Hosts
 
 

Highbush and lowbush blueberry

 
     
 
Biology
 
 

Season

 
 

One generation per year:

 
     
 

Behavior

 
 

Adults are active only in the day, and especially on warm days.

 
     
 

Life Cycle

 
 

The larvae feed in individual cells within the gall. They overwinter in the gall and pupate in the spring. Adults emerge from late May to early June before the host buds break.

 
     
 

Larva Food

 
 

Blueberry stem tissue

 
     
 

Adult Food

 
 

 

 
     
 
Distribution
 
 

Distribution Map

 

Sources

24, 27, 29, 30, 82, 83.

 
  11/17/2023      
         
 

Occurrence

 
 

Common

 
         
 
Taxonomy
 
 

Order

Hymenoptera (ants, bees, wasps, and sawflies)  
 

Suborder

Apocrita (narrow-waisted wasps, ants, and bees)  
  Infraorder Proctotrupomorpha  
 

Superfamily

Chalcidoidea (chalcidoid wasps)  
 

Family

Ormyridae  
 

Subfamily

Ormocerinae  
 

Genus

Hemadas  
       
 

This is the only species in the genus Hemadas.

 
       
 

Synonyms

 
 

 

 
       
 

Common Names

 
 

blueberry stem gall wasp

 

 

 

 

 

 

Glossary

Femur

On insects and arachnids, the third, largest, most robust segment of the leg, coming immediately before the tibia. On humans, the thigh bone.

 

Gall

An abnormal growth on a plant produced in response to an insect larva, mite, bacteria, or fungus.

 

Gaster

The bulbous part of the abdomen of ants, bees, and wasps. In ants it usually begins at segment three.

 

Ovipositor

A long needle-like tube on the abdomens of some female insects, used to inject eggs into soil or plant stems.

 

Scape

On plants: An erect, leafless stalk growing from the rootstock and supporting a flower or a flower cluster. On insects: The basal segment of the antenna.

 

Tarsus

On insects, the last two to five subdivisions of the leg, attached to the tibia; the foot. On spiders, the last segment of the leg. Plural: tarsi.

 

Tibia

The fourth segment of an insect leg, after the femur and before the tarsus (foot). The fifth segment of a spider leg or palp.

 

 

 

 

 
 
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Luciearl

 
    blueberry stem gall wasp   blueberry stem gall wasp  
           
 
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Other Videos
 
  Blueberry gall wasps, Hemadas nubilipennis
Endless Forms
 
   
 
About

Sep 8, 2018

These tiny wasps (𝘏𝘦𝘮𝘢𝘥𝘢𝘴 𝘯𝘶𝘣𝘪𝘭𝘪𝘱𝘦𝘯𝘯𝘪𝘴) induce stem galls in blueberries (𝘝𝘢𝘤𝘤𝘪𝘯𝘪𝘶𝘮), where their larvae develop. From Dr. Patrick Edger, Department of Horticulture, Michigan State University.

 
  Emergence, blueberry stem gall wasp
John van der Linden
 
   
 
About

Nov 9, 2017

Adult blueberry stem gall wasp, Hemadas nubilipennis, chewing its way out of a gall on wild lowbush blueberry, Vaccinium angustifolium

11 May 2017

Iowa, USA

 

 

Camcorder

 
 
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  Luciearl
10/12/2023

Location: Fairview Twp.

blueberry stem gall wasp  
           
 
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Created: 11/17/2023

Last Updated:

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