RI Apple IPM Newsletter

From Heather Faubert and Steve Alm

The recorded pest message is operating now. Call (401) 949-0670 between 5:00PM and 8:00AM for the weekly message. New messages are usually recorded on Wednesday. Updates to the Rhode Island Apple IPM Website are made at least twice weekly. The address ishttps://www.uri.edu/research/ipm.

The wet weather starting out this season may lead to severe problems. This is not a year to be casual about fungicide applications. This seems to be an excellent year to use sterol inhibiting fungicides or the new Strobilurine fungicides. The Strobilurine fungicides (Sovran and Flint) are a new class of fungicides produced originally from a forest floor mushroom, Strobilurus tenacelius. They protect against apple scab for 3 – 6 days and have a 4 day post-infection activity (kick-back action).

Dan Cooley, from UMASS, wrote this about the new Strobilurines:
New class of fungicides, effective against scab and flyspeck
Environmentally benign (low mammal toxicity)

Potential for resistance development

Dealing with resistance:
Do not apply more than 3 sequential applications of a strobilurine
Do not apply more than 4 applications per season
Do not apply more than 11 oz. Flint or 22 oz. Sovran per season
Consider tank-mix with a broad spectrum fungicide

The Strobilurines are not Sterol Inhibiting fungicides:
They have a 7 – 10 day effective interval between applications, but…
Protectant activity is about 3 – 6 days
Post-infection about 4 days
Exceeding the 4 day post-infection period probably won’t stop lesion growth,
though it might stop spore production.

Sovran 4 – 6.4 oz./acre
Flint 2 – 2.5 oz./acre
12 hour re-entry period

Apple blotch leafminer adult moths have been caught on red sticky traps since early April and eggs have been seen since April 18. Leafminer populations appear to be much lower this year than last year where we caught record number of adults. Still, leafminers will be a problem in some orchards. Look on the underside of cluster leaves for the small, pale, gelatinous eggs. The eggs are easiest to see on smooth, hairless leaves such as Red Delicious. A good threshold is probably 13 eggs per 100 leaves. To control leafminers we recommend applying Provado or AgriMek at petal fall. AgriMek must be mixed with an adjuvant to be effective. Supposedly an oil spray, such as Sunspray Ultrafine Oil, works better as an adjuvant than LI-700 or Silwet. Of course, combining AgriMek with oil interferes with using Captan. Don’t use Captan within two weeks of an oil application.

European red mites started hatching by April 25. Do not delay applying oil against red mites. This has been an extremely difficult season for applying oil so it will be necessary to assess mite populations at petal fall. Look for mite nymphs during bloom and plan for a control at petal fall if you find one mite per leaf. Use Apollo, Savey or AgriMek. Remember, if you used Apollo or Savey last year, don’t use it this year. If you used AgriMek last year, don’t use it this year.

Rosy apple aphids have been found in some orchards. They will attack all apple varieties, but varieties such as Cortland, Idared, Golden Delicious are particularly susceptible. Rosy apple aphids are usually pinkish, sometimes varying to light brown, slate grey, or greenish black. The body is covered with a whitish coating and can be found in curled up leaves.

Sample 10 clusters from interiors of susceptible trees; sample 10 trees per block. NY researchers recommend spraying at pink if you find even one colony of rosy apple aphid. Thiodan or Lorsban at pink will control rosy apple aphid. Synthetic pyrethroids (such as Pounce or Asana) are also effective but we do not recommend them since they are harmful to predatory mites. Provado used at petal fall against leafminers will also control rosy apple aphids.

The May Twilight Meeting will be on May 11, at 5:30 at Sunset Orchards in North Scituate, RI. The orchard is located on Gleaner Chapel Road. See you there!

The 2000 – 2001 New England Apple Pest Management Guide is now available and it is beautiful, complete with color pictures! The cost is $8.00 a copy if you haven’t paid your RI Fruit Growers Association dues.