RI Apple IPM Newsletter
May 2, 1997
From Heather Faubert and Steve Alm
We hope everyone is off to a good start and have been able
to apply good, thorough oil applications for European red mite
control. We saw a few hatched red mite eggs on April 30th. Once many eggs
have hatched, oil applications are much less effective. For those of you
who did not get on an adequate oil application and did not use Apollo
or Savey prebloom, consider using Agrimek at petal fall. Agrimek (2.5
oz./100 gals. or 10 oz./acre) in combination with horticultural oil (3
pints/100 gals or 1 gal./acre) should give excellent control of red mites.
Agrimek must be mixed with oil or it will be ineffective. Of course, once
you mix oil in your petal fall spray you must not use Captan for 7 - 10
days following the application. Agrimek will also control apple blotch
leafminer when used at petal fall - so if you know you need to control
leafminer it is really an excellent chemical choice.
A little bit more about Agrimek since it is really new to us: Agrimek
gets absorbed into the leaf and gives long, residual activity even under
heavy rainfall. It is suppose to be harmless to most beneficial predators
and parasites but highly toxic to bees. Do not apply while bloom remains
on trees but you need to apply it at petal fall to be most effective against
mites and leafminers.
European red mites can easily become resistant to miticides. To preserve
the effectiveness of these new materials it is extremely important not
to use the same miticide two years in a row. Also, you must consider Apollo
and Savey as the same pesticide for the purpose of resistance. In other
parts of the world growers have found resistance to Apollo and Savey after
just 3 or 4 years of once a year applications.
Apple blotch leafminer trap captures are above the threshold of
21 adults per trap by pink in 7 out of 10 monitored orchards. Usually
we get about half of monitored orchards above the threshold so this year
we have more than usual above the threshold. If you did not monitor your
orchard with red sticky traps you can still scout your orchard for leafminer
eggs and decide if a petal fall treatment is necessary. From pink to bloom
look for the eggs on the under side of the oldest fruit cluster leaves.
The eggs are pale yellow-clear gelatinous, flattened discs. The eggs are
larger than red mite eggs but difficult to see because of the pale coloring
- you must use a handlens to see them. Check the oldest 3 or 4 leaves
on a cluster and check 3 clusters per tree and at least 3 trees in a block.
If you find more than 2 eggs per cluster (not leaf, but cluster), apply
Provado at petal fall. (Agrimek plus horticultural oil at petal fall will
also control leafminer).
Provado (2 oz./100 gals.) is very effective against leafminer and will
also control white apple leafhopper. Provado is highly toxic to bees but
is not harmful to predatory mites. Now that we have Provado and Agrimek
to use against leafminers, we see no reason to use synthetic pyrethroids
(Ambush, Pounce, or Asana). The synthetic pyrethroids are very toxic to
Tarnished plant bugs have been caught in most orchards on white
sticky traps but have reached the threshold of 5 per trap in only one
orchard. Generally, orchards have not required a prebloom insecticide
for tarnished plant bug. This year we are catching a few more than we
have for the last several years, but still the trap captures are below
the spray threshold. It is difficult to control tarnished plant bugs anyway.
They are only fairly controlled by Guthion, Imidan or Lorsban and although
synthetic pyrethroids are quite effective against tarnished plant bugs,
we don't recommend their use because they are so toxic to predatory mites.
Speaking of preserving mite predator populations: choosing fungicides
to protect predator mite populations may be as important as choosing gentle
insecticides. Repeating information that was sent to you in February:
Recent research has shown that the EDBC fungicides (Dithane, Manzate,
Penncozeb, Maneb, Manex, and Polyram) and Ziram are harmful to predator
mites. In studies in New York, mite predator populations were reduced
by 50% after using EDBC fungicides for one season. Also, after looking
at spray records from RI apple growers I noticed that 2 out of 9 growers
had not used any EDBC fungicides for the past 4 years. These same 2 growers
had not needed to apply a miticide for the past 4 years!
Experience has told us that not everyone is going to abandon EDBC fungicides
just like that! We have persuaded a few growers to give up their EDBC's
and we'll let you know what happens in these orchards. We are especially
interested to see what happens in orchards where we released the mite
predator T. pyri last year. This year we will be collecting flower and
leaf samples and sending them to New York where they will look for T.
pyri. If EDBC fungicides do harm predator mites, would should be able
to find out this year.
We are participating in a New England wide project to get information
about growing apples on the internet. It is also a place for growers to
exchange ideas. The Apple Information Manager (AIM) is a growing web site
and can be accessed at http://orchard.uvm.edu/AIM/
We hope to have a demonstration ready for you at our next Twilight meeting
(May 27th at Paul Lamore's orchard in North Kingstown).
The recorded pest message should be up and running by May 5th. Call 949-0670
between 5:00PM and 8:00AM for the latest message.
If you have not received your copy of the 1997 Update to 1996-97 New England
Apple Pest Management Guide (handed out at Annual Meeting and Twilight
meeting) then call Heather Faubert at 874-2750.
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