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 predatory mites.

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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