Notes on Raspberry Insects
Two-spotted spider mite
Identification
Use a 10-14 × magnifying hand lens to see mites properly. Adult
mites are 0.3-0.5 mm, greenish-yellow with two dark spots on the back.
Nymphs are similar in appearance only smaller. Eggs are clear and round.
All stages occur predominantly on the lower leaf surface.
Two spotted spider mite damage
showing webbing and leaf stippling
Period of Activity
Female two-spotted spider mites overwinter in crop debris
on the ground. The overwintering adults are orange in colour. In spring
they move to new growth and feed on leaves closest to the ground. There
are many generations per year and eggs, nymphs, and adults are frequently
present at the same time. As populations build and leaves age or become
damaged, mites move up the plant to newer, more succulent growth. The
time for one generation to develop, from egg to mature adult, ranges from
to five days at 24ºC to three weeks at 12ºC.
Monitoring
Most field-grown raspberry plantings will not have a problem with mites.
However, when raspberries are grown in greenhouses or high tunnels, mites
can be a major problem. Certain varieties like Autumn Britten are susceptible
to mites both in protected culture and in the field.
Observe the plants weekly for signs of mite damage, which first appears
as flecks and stipples on the leaves. Collect leaf samples from mid-way
along the cane and examine the lower surface for all stages of mites.
Record the presence of beneficial insects such as syrphid larvae, ladybird
beetle larvae and predatory mites.
Two-spoted spider mite damage and
defoliation
Management notes
There are no thresholds for spider mite control on raspberries. Control
mites if damage is evident and populations increase from week to week.
Beneficial insects reduce the need for miticides. There are several miticides
available for raspberries. Each has a different mode of action and acts
best against a certain stage of mite. Apply each product when most mites
are at a susceptible stage for that product. See Table 1. Miticides Registered
on Raspberries. Use different products from year to year to prevent the
development of resistance.
Table 1. Miticides Registered on Raspberries
| |
Stage of mite controlled |
Comments |
For use before harvest |
For use after harvest |
| Apollo SC |
Eggs, very young nymphs |
Should be applied when most mites are in the egg stage. This miticide
works best if applied early in the season, when generations tend to
be most synchronous. |
X
|
|
| Kelthane 50 W |
Nymphs |
An older product. Resistance to Kelthane has developed where it
has been used repeatedly. This miticide works slowly; do not expect
rapid knockdown of mites. |
X
|
X
|
| Agri-Mek 1.9% EC |
Adults, nymphs |
Translaminar (locally systemic). Absorbed best by new, expanding
leaves. |
|
X
|
| Pyramite |
Adults, nymphs |
A contact miticide providing rapid knockdown of adults and nymphs.
|
|
X
|
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