Arthropod Management Update

For those who do not have access to our website (http://orchard.uvm.edu/), the following is an update of accumulated DD (Base 50F) that can be used in conjunction with the table on arthropod 'events' that first appeared in the April issue of the Vermont Apple Newsletter and which is inserted below.

Apple Maggot (AM)

Through mid-July, trap captures that were reported both in Vermont and across much of New England were progressing slowly. This week trap captures noticeably increased at the UVM Hort.Res.Center.   It is expected that captures will continue to increase, particularly if we get some rain.   If you have had your traps out for 2-3 weeks, now is the time to clean them of debris.  Massachusetts researchers estimate that the traps' ability to capture apple maggot flies decreases by approximately 25% for every week of exposure without maintenance. 

Current Threshold:  cumulative average of 2/trap on non-baited spheres  or  5/trap for baited spheres.   If an insecticide for apple maggot is applied, trap captures should be discounted while there is effective residue present.

European Red Mites (ERM)

In talking with growers from VT and NY during the orchard tour in the Peru/Chazy area  on July 15, European red mite populations are below what might be expected in many orchards given the very dry, hot conditions.  The  action threshold from July 15- August 15 = 80 % of middle-age terminal leaves with motile mites.  Again, page 111 of the 1998-1999 New England Apple Pest Management Guide lists options if mites are over threshold.

Leafminers (LM)

Depending on where you are in the state,  second generation LM mines may be at the point where over 10%  are in the tissue-feeding stage - which would be late for treatment.    Thresholds for the second generation mines are:  50 mines/100 McIntosh leaves;  100 mines/100 Non-McIntosh leaves.    If you are above threshold and less than 10% of the second generation mines are in the tissue feeding stage, Provado or SpinTor would be options that have the least impact on the beneficial arthropods in your orchard. 

The following graph is the average new trap captures per week at the UVM Hort.Res.Center from four spotted tentiform leafminer pheromone traps.  You can see that first flight peaked on May 3 at an alarming high number.  However, we never reached threshold levels with first generation mines and it appears the second flight will not peak as high as the first. 

Codling Moth (CM)

If you have a problem with CM in your orchard, an insecticide such as Imidan or Guthion, applied between 1260-1370 Degree Days (base 50F) from the first pheromone trap capture will target the second generation.   At the UVM Hort.Res.Center, we trapped our 1st CM on May 18th and have accumulated approximately 1161 DD.  Codling moth flight and degree days will vary around the state but suffice to say the window for managing second generation CM is upon us.

If you are monitoring CM activity in your orchard, you may be interested in comparing your flight activity with the following graph which shows the average new trap captures per week at the UVM Hort.Res.Center from four pheromone traps.