Dormant spur sampling for prunes.
This technique can also be used to monitor for these pests in plum and almond. (View with transcript)
Dormant spur sampling is used to determine the need for a dormant
treatment to control San Jose scale, European fruit lecanium, European red
mite, and brown mite. If mealy plum aphid and leaf curl plum aphid were not
treated in early November, also record the presence of aphid eggs in the
dormant spur sample. Spurs are the short shoots containing the flower buds.
Dormant spur samples are taken once a year between mid-November and the end of
Use the sampling
form(PDF) with detailed treatment threshold information
for dormant spur sampling.
Take a sample between mid-November and mid-January.
Randomly select 35 to 50 trees from each orchard or plot to be sampled.
Select 2 to 3 spurs randomly from the inside of each tree's
canopy near the main scaffold. Continue until you have collected a total of 100
spurs. It is important to choose spurs on older wood because they are much more
likely to be infested.
Clip the spur off at the base, making sure to include some
old spur wood along with the past season's growth to detect parasite activities
Using a hand lens or binocular microscope, examine the
spurs and note the presence or absence of scales and parasitized scales, aphid
eggs and mite eggs on the sampling form. It is not necessary to count the
number of individual insects or mite eggs present, just identify the pest and
record whether it is present or not.
A parasitized scale can be
distinguished from a live scale by a small hole in the top of the scale
European fruit lecanium scales turn black. If a
large number of scales have been parasitized, minimize the use of insecticides
during the growing season, and use those that are not harmful to parasites so
that naturally occurring parasite populations will not be destroyed.
1 See the San Jose scale section for more
information about treatment choices according to infestation levels.
CHOICE OF INSECTICIDES
Oils alone are effective against the white
cap and black cap stages of San Jose scale, which are present at this time, and
will also control low-to-moderate populations of mite eggs and fruittree
Other pests such as peach twig borer and obliquebanded
leafrollers will not be controlled by oil alone during the dormant season.
Environmentally sound insecticides such as Bacillus thuringiensis, spinosad (Entrust, Success), methoxyfenozide
(Intrepid) and diflubenzuron (Dimilin), however, applied at bloom will control
peach twig borer and leafroller caterpillars.
The combination of these bloom
time treatments along with a dormant oil application for scales, mite eggs, and
leafroller eggs is a good IPM strategy for many orchards.
Organophosphates applied during the
dormant season for peach twig borer are particularly vulnerable to run-off into
waterways and should be avoided.
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