INSECT and MITE PESTS

Tarnished plant bug (TPB) trap captures remained quite low at Highmoor Farm up to Wednesday, May 14, when McIntosh buds were at late Tight Cluster.  I use 4 traps per block in 4 blocks (16 traps total). 

       The cumulative average per trap in 4 blocks was: 1.5,  1.0,  0.5,  and 0.3.  The threshold at Tight Cluster for a retail apple crop is 5 per trap.  The wholesale crop threshold at that time is 3 per trap.  At Pink the thresholds are 5 per trap wholesale, and 8 per trap for retail production. 

        I will be checking traps again on Monday May 19 and expect that with warm weather over the weekend the counts will have increased.  But I don't expect the updated counts to be high enough to warrant a prebloom insecticide treatment against TPB.

Leafminer captures in those same four blocks was a cumulative average per trap of:   >70,  9.5,  1.0,  and 0. 

        Leafminer trap thresholds from Massachusetts are 9 leafminer moths per trap from silver tip to Pink for McIntosh or other trees prone to preharvest drop.  The threshold for other cultivars or non-stressed trees is 21 per trap. 

        However, leafminer trap counts are not always accurate predictors of where mines will actually appear.  This may be due to behavioral differences between the two leafminer species, and also to the influence of weather on leafminer mating and egglaying success after the traps are read at Pink.  I will be doing leaf mine counts shortly after Petal fall.

Looking ahead to Petal Fall

        Guthion has been out of the Highmoor apple spray program for several years.  Because of hazardous materials reporting hassles invoked by Imidan, Highmoor Farm manager Justin Jamison is planning a non-organophosphate insecticide program on apples this year.  This essentially means choosing between Avaunt, Assail, and SpinTor to control plum curculio, leafminers, codling moth, leafrollers and apple maggot.  There are of course additional options effective against a narrower range of pests, but as a group these three are the closest to matching Imidan's utility against a variety of insect pests. 

        Actara would be in that group had it's manufacture for use on apples been discontinued.  If you have existing stock with apples on the label, that can be used according to its label.

        The plan is to alternate between materials.  This is to prevent resistance in those pest species prone to it (codling moth, leafrollers, and leafminers).  Resistance doesn’t seem to be an issue with plum curculio or apple maggot, probably because of the large populations on wild host trees outside the orchard diluting genetic selection pressure for resistance.

          Avaunt can not be used more than 4 times per season.  Four postbloom insecticide applications per year is the norm at Highmoor (Petal fall, First cover, late July, mid-August).  However, it would preferable not to lean too hard on a single product.  And a four spray limit doesn’t leave any flexibility for special cases that might arise.  So it would be good to use an alternative to Avaunt when one of the other materials can meet the need.

  

        If the TPB counts are over threshold, that would be a reason to choose Avaunt at Petal fall.  Another reason would be if European apple sawflies are over threshold. 

        I set EAS traps last week and will be make an initial check on Monday, May 19, but it is really too early to gauge the EAS pressure at Highmoor this year.  Trap counts at Petal fall are a useful indicator.

        If neither TPB or EAS looks like much of a problem, but leafminer does, then Assail might be the better choice for Highmoor at Petal Fall.  Avaunt is the better choice for plum curculio, but PC risk is lower at Petal fall than at First cover.  Also, even though Assail is not labeled for plum curculio at preset, a sales rep for Assail says they expect to add plum curculio and EAS to the label for next year.  However, that is speculative at this point..

        Cornell gives Avaunt a “Fair” rating against leafminers, but leafminers are not listed on the label I checked.  Assail is a new insecticide that should be fully effective for leafminers.

        If Avaunt goes on at Petal fall, there is the option to use Assail at First cover, especially if leafminer is a concern.  An argument in favor Assail at First cover is that it might provide better protection against first generation codling moth.  But using a product without plum curculio on the label at First cover is a harder call than doing so at Petal fall, and requires some thought and investigation about how much risk of plum curculio damage that might leave.

European red mite egg hatch is underway.  Petal fall is a good time to check for mites.  If oil application was effective there should not be many mites to find.  The threshold until June 15 is an average of 1 mite per leaf, or living hatched mites present on 30% of middle-aged (i.e. middle of the shoot) interior fruit cluster leaves.  If mites are over threshold at Petal fall, some of the control options are Apollo, Savey, Agri-Mek, and Vendex.  These materials are effective for early season use, but less effective against a resurgent late summer mite outbreak.