RI Apple Newsletter
May 29, 1998
From Heather Faubert and Steve Alm
Recorded pest message is available between 5:00PM and 8:00AM
daily. Call (401) 949-0670.
Here is your 1998 -1998 New England Apple Pest Management Guide!
We are certainly past primary scab season now! Lesions from
the intense wet spell of May 4 - May 11 have probably all appeared by
now. Check now to see how thoroughly you controlled primary apple scab.
Since a scab lesion can continue to produce conidia for 4 weeks once it
forms, it is advisable to apply fungicides to try and burn out the lesions.
These fungicides reduce the number of conidia produced on lesions and
reduce the ability of existing conidia to germinate. Because of the need
to cover all scab lesions with fungicide, relatively high volume, low
concentrate applications (no more than 4x) will give the best results.
Try two full-rate captan applications 5-7 days apart. Read more about
eradicating scab on page 15 of the Pest Management Guide.
If you are scab free, or close to it, you can switch to your summer fungicide
schedule. We recommend either Captan every two weeks or Captan plus Benlate
every three weeks.
If you have applied a full rate of Imidan or Guthion since May 24 or so,
you should be finished controlling plum curculio for the season.
We did find two plum curculio adults feeding in an orchard this week that
had not received an insecticide for 14 days. Continue to monitor trouble
spots for late plum curculio activity. Perhaps a border row spray would
be warranted if you find fresh plum curculio egg laying scars 10 - 14
days after the last insecticide treatment. Fresh scars are crescent shaped
slits that have very little callus tissue associated with them.
This could be a very big year for European red mites! In one orchard
this past week we found plenty of red mite eggs where we had found very
few, if any, red mite adults the week before. This early hot, dry weather
could lead us into a very difficult mite season. The spray threshold until
June 30th is 2.5 motile mites (not eggs) per leaf or 62% of leaves with
any number of motile mites. Once this threshold is exceeded a miticide
should be applied. Pyramite is a very effective miticide but should be
used only one time per season so the mites don't build up resistance too
quickly. It is labeled for no more than two applications per season. After
Pyramite, what do we have? It is too late in the season for Apollo, Savey,
or Agri-Mek. Kelthane and Vendex have not been effective and Carzol is
very damaging to predatory mites. There is also the option of using ultra
fine oils. Call the recorded pest message to hear updates on results of
different strategies attempted for mite control.
Apple blotch leafminer can be found now as sap feeding mines and
tissue feeding mines. The larvae have begun to pupate in the mines; adults
will begin to emerge in a week or two. Now is not the time to apply
pesticides against leafminer - the mines are too far advanced to be controlled
properly. If you are finding more than 7 - 14 mines per 100 fruit cluster
leaves, consider treating for the second generation mines with Provado
around the third week in June. Since the second generation is more spread
out than the first generation, often two applications of Provado are needed
to adequately control second generation leafminers.
Green apple aphid colonies are starting to build up on terminals
and suckers in some orchards. I expect next week we will begin to find
many of the predators that feed on aphids. In nearly all cases the predators
will adequately control aphids without the use of pesticides. The two
most common aphid predators are the syrphid fly larvae and the cecidomyiid
larvae. The syrphid fly lays small, long, white eggs among aphid colonies.
The eggs hatch into small, motiled green and brown larvae that feed on
aphids. The cecidomyiid eggs and larvae are bright orange. Both species
feed by sucking fluids from aphids and leave behind shriveled, blackened
aphid cadavers. Spraying Thiodan or Provado against aphids is only warranted
if aphid honeydew starts accumulating on the fruit.
We haven't seen many white apple leafhoppers this year. Many growers
have applied either Agri-Mek, Provado, or Sevin at 1 lb/100 gal. which
control white apple leafhopper. Check areas in your orchard that were
not treated with any of these chemicals. The small, pale nymphs can be
found on the underside of older leaves. White apple leafhopper feeding
removes sap from leaves, causing stippling that may coalesce into silvery,
white patches. Leafhoppers are easiest to control when they are small,
first generation nymphs from petal fall to early June. White apple leafhoppers
have developed resistance to several organophosphate insecticides so Guthion
or Imidan will not control them. If you do find many leafhoppers control
with Thiodan or Provado at 1 oz./100 gal.