Cornell Cooperative Extension
Swede Midge Introduction,
Damage and Biology
Christy Hoepting
Cornell Cooperative Extension
Vegetable Program
Swede Midge
• Serious insect pest of cruciferous plants:
– vegetables (i.e. broccoli, cauliflower, Brussels
sprouts, cabbage, collards, swede/turnip,
Asian vegetables (i.e. bok choy, etc.)
– canola
– weeds (i.e. shepherd’s purse, wild mustard)
– Ornamental crucifers
• Common and endemic in Europe:
– Known since late 1800s
– Major pest in Belgium, Germany, Switzerland,
Netherlands, France, Poland and Slovania
Swede Midge in North America
• 2000: first identification in Ontario, Canada
(Hallett & Heal)
– Symptoms observed at least since 1996, but
erroneously attributed to a molybdenum deficiency
• Economic losses occur in Canada and in parts
of New York State:
– up to 85% losses
– Especially in organic and small-scale operations
Swede Midge: Adult
Adult female
Adult male
Swede midge: eggs
Length: 0.3 mm
Width: 0.08 mm
Deep in the youngest actively growing vegetative tissue
Swede midge: larvae
0.3 to 3-4 mm
Damage: Blind head,
brown scarring at growing point
broccoli
Damage: Leaf puckering
Green cabbage
Damage: Leaf puckering
broccoli
Damage: Leaf puckering
Red cabbage
Damage: Leaf puckering
cauliflower
Damage: Multiple shoots,
growing points
broccoli
Damage: Multiple small heads
Red cabbage
Damage: Brown corky scarring in head
cauliflower
Damage: Brown corky scarring in head
broccoli
Damage: Brown corky scarring in head
Green cabbage
Damage: Secondary soft rot
Swede midge larvae in an infested
growing tip
Damage: Swollen Flower Buds
Damage: Swollen Florets
broccoli
Swede midge damage in canola
Swede midge damage on weeds
Field pennycress
Swede Midge Damage Severity
Increases…
• as number of larvae per
plant increases
• the earlier in
development that the
plant is infested
• later in the season as
the population builds
• in sheltered areas near
hedgerows, buildings,
treelines
Crucifers are susceptible to swede midge all season long
Swede Midge Life Cycle
3 days
drought
Transparent to
creamy white
2-50 eggs/cluster
100 eggs /female
Mating
1-5 days
Soil
moisture
Eggs ~0.3 mm
Adults ~1.5 to 2 mm
4-5 over-lapping generations
Larvae ~0.3 to 3-4 mm
21-44 days
per generation
Emerge
Transparent on first hatch to yellow
when mature, feed gregariously at plant growing tip
mid-May
7-21 days
7-14 days
Pupae ~2-4 mm
Overwintering
Cocoons
May-June
July
July-August
August
Sept - Oct
Survive in soil > 1 year
Pre-pupae
most within top 2 cm of soil,
Optimum 25-75% soil moisture
for emergence
Ju
n
Ju 2-J
n un
5
Ju - J 5
u
n
8 n
Ju -Ju 8
n1 n
Ju 3- 13
n Jun
1
Ju 6-J 16
u
n
20 n 2
Ju -J 0
un
n
Ju 23- 23
n Ju
27 n
27
Ju Jun
n
30 30
Ju -Ju
l4 l4
Ju - Ju
l7 l
Ju -Ju 7
l1 l1
0
0
Ju -Ju
l1 l1
Ju 4-J 4
l 1 ul
8
1
Ju - Ju 8
l2 l2
Ju 1-J 1
l 2 ul
5
2
Ju - J 5
l 2 ul
8
2
Ju - J 8
l 3 ul
1
3
Au - A 1
u
g
g
Au 4 - 4
A
g
Au 8 - ug
A 8
g
1 u
Au 1 - g 1
A 1
g
1 u
Au 5 - g 1
A 5
g
1 u
Au 8 - g 1
A 8
g
2 u
Au 2 - g 2
A 2
g
25 ug
25
Au g Au
30 g
- S 30
ep
t5
Total # SM Captured on 3 Traps
2006 Swede Midge Trap Activity –
Ontario, Canada
450
400
Wellington Cty
Hamilton/Wentworth Cty
Simcoe Cty
350
300
250
200
150
100
50
0
J. Allen, M. Paibomesai and H. Fraser, 2006