4. A.Root-feeding Pests
The most common root-feeding pests of
strawberries in Illinois include the strawberry
crown borer, Tyloderma fragariae, the strawberry
root weevil,Otiorhynchus ovatus, and white
grubs in the genus Phyllophaga. Other below
ground pests, including the strawberry
rootworm, Paria fragariae and strawberry root
aphid, Aphis forbesi, are rarely economically
important in Illinois. Although the crown borer,
root weevil and grubs are all members of the
insect order Coleoptera (the beetle and weevils)
their life histories differ considerably.
5. 1. Straw berry Crown borer
Damage Strawberry corn borer
Although adults eat small
holes in leaves in the fall, this
defoliation rarely is
economically damaging. Larval
feeding is far more harmful. As
one or more larvae bore
downward through strawberry
crowns, plants are weakened,
stunted, or killed. Field
borders or the portions of
fields nearest older, infested
plantings are often most
heavily damaged
Strawberry corn borer adult and
larva.
Adult is about 1/3 inch (8 mm)
long;
larva is about 1/4 inch (6 mm)
long.
6. 2.Strawberry Root Weevil
Otiorhynchus ovatus
Damage Weevil
Root weevil adults lay eggs in
strawberries throughout the
summer, with each female
depositing 150 to 200 eggs in the
soil. Eggs hatch in about 10 days,
and larvae burrow through the soil
to feed on roots until they mature
or until cold temperatures cause a
suspension of their activity.
Damage to roots and crowns
caused by root weevil larvae can
weaken, stunt, or kill strawberry
plants. Although adults eat
notches from the edges of leaves,
their feeding causes no economic
loss.
Strawberry root
weevil.
Adult is about 1/3
inch (8 mm) long;
larva is about 1/4
inch (6 mm) long.
7. 3.White Grubs
Phyllophaga spp
Damage White Grub
Females deposit eggs in soil during late
spring or early summer; they especially
prefer grass sod near wooded areas for
egg-laying. As a consequence, damage
caused by larvae is greatest in crops
grown on sites that were grass-covered
the previous season. Newly-hatched
larvae feed on crop roots throughout
the summer, then burrow deep in the
soil to overwinter. The following year
they again migrate to the root zone to
feed. These larger larvae cause much
greater damage than they did the year
before. After overwintering again well
below the soil surface, white grubs
pupate early in the following summer,
and adults emerge from pupal cells in
the spring three years after the cycle
began.
White grub adult and larva.
Adults of common species
range from 1/2 to
1 inch (12 - 25 mm) in
length;
C-shaped larva may exceed
1 inch in length
8. B.Foliage-feeding Pests
The foliage-feeding pests of strawberries in
Illinois include leafrollers (strawberry leafroller
and others), the strawberry rootworm and two
mite species—the two-spotted spider mite and
the cyclamen mite. This summary reviews the
life histories of these pests and the practices that
can be used for their management. Other
foliage-feeding pests, including the grape
colaspis and strawberry sawflies rarely damage
strawberries in Illinois and are not covered in this
paper. Information on these less common pests
is summarized in Insect Pests of Strawberries in
Ohio (Williams and Rings, 1980
9. 1. Leafrollers
Ancylis comptana fragariae
Damage Leaf Roller
As larvae feed, they secrete silken
threads to fold and tie strawberry
leaflets together. Within these
folded leaves, larvae feed on only
the epidermis of each leaf, but
entire leaflets usually turn brown.
The strawberry leafroller
completes 2 or 3 generations of
development each year, and moths
of the summer generations are
often present from July through
September. Infestations may
develop in spring and early
summer, but they may also build
up after harvest.
Strawberry Leafroller,
adult and larva.
Adults wingspan and
larval length are
about 1/2 inch.
10. 3.Slugs
Agriolimax spp. and Arion spp
Damage Slug
Slugs damage fruit by eating deep
holes into the surface of berries.
Slugs that damage strawberries in
Illinois in the spring and early
summer hatched from eggs
deposited in strawberry plantings
the previous fall. Conditions that
favor egg-laying in the fall include
the continuous presence of straw
mulches. Slug survival and fruit
damage in the spring are greatest
in dense, wide rows and when
overcast and rainy weather creates
continuously moist conditions in
strawberry beds.
Gray garden slug.
Most slugs in
strawberries range in
length from 1/2 to 1
1/2 inches (12 - 36
mm).
11. 4.Strawberry Clipper
Anthonomus signatus
Damage Clipper
Adult clippers first feed on immature
pollen by puncturing nearly mature
blossom buds with their snouts. The
female then deposits a single egg inside
the bud and girdles the bud, preventing
it from opening and exposing the
developing larva. The adult female then
clips the stem so that the bud hangs
down or falls to the ground. Larvae feed
within the damaged bud for a period of
3 to 4 weeks; a new generation of
adults emerges in late June and July.
These weevils feed on the pollen of
various flowers for a short time, but
seek shelter in midsummer in
preparation for overwintering.
Strawberry clipper
(aka strawberry
weevil) Adult is 1/10
inch (2.5 mm) long.
12. 5.Strawberry Sap Beetle
Stelidota geminata
Damage Sap Beetle
Their feeding leaves deep cavities
in berries, and females then
deposit eggs on the injured fruit.
Although larvae feed in berries,
they usually are unnoticed because
the fruit has already begun to
decompose as a result of damage
caused by adults. Because over-
ripe fruit is especially attractive to
sap beetles, damage is often
greatest in U-Pick operations
where pickers leave large numbers
of ripe and over-ripe berries in the
field.
13. 6. Tarnished Plant Bug
Lygus lineolaris
Damage Bug
Several generations of this insect
develop each year, and adults and
nymphs are present on many
different plants from April or May
until a heavy frost in the fall.
Tarnished plant bugs use
piercing/sucking mouthparts to
feed on sap from flower buds. As
they feed, they inject a toxin that
kills surrounding cells. This results
in berries that remain small, with a
concentration of seeds at the end
of each ripening berry. These
distorted "button berries" remain
woody and unmarketable.
Adult Tarnished Plant
Bug. Length is 1/4
inch (6 mm)