WNC Orchard Insect Pest Populations – July 27, 2021

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Codling Moth and BMSB are Key Target Pests

Codling moth: Degree-day accumulations range from about 1770 in Henderson County to 2220 in Cleveland County. This coincides with completion of 32% hatch of second generation eggs in Henderson to >80% in Cleveland. In orchards with low pheromone trap captures there should be no need for additional insecticides targeting this generation. While there will definitely be sufficient heat and time for a third generation in lower elevations, this generation is only a concern when high levels of control were not achieved in earlier generations.

Newly-molted adult brown marmorated stink bug and nymphBrown marmorated stink bug: The figure below shows predicted emergence of first generation brown marmorated stink bug adults, the most damaging stage on apples and other crops. The line shows that emergence begins at about 740 DD (biofix is 4 April) and is nearly complete at about 1400 DD. As of today (27 July), about 25% of adults have emerged in the lower elevation of Cleveland County (831 DD), but emergence has not yet begun in Wilkes (684 DD) or Henderson (591 DD). An initial insecticide application is recommended at about 10% emergence, or 780 DD, so now is an important time to protect crops in lower elevation orchards.

Based on the weather forecast, 780 DD is predicted for 3 August in Wilkes County, but not for about two weeks in Henderson County and higher elevations. However, in some locations we have trapped high numbers of overwintered adults, so an earlier application may be warranted on highly susceptible cultivars such as Granny Smith and Pink Lady.

Emergence chart image

Apple Maggot:  As of yet we have not detected emergence of apple maggot flies in our abandoned orchard in Henderson County. Emergence of apple maggot begins about 1 August, so first capture should not be far off. Remember that insecticides recommended for BMSB also control apple maggot, and orchards adjacent to an abandoned orchard are most susceptible to damage.

Learn more about southeastern apple insect pests at the Apple Insect Management page.

2021 Average Weekly Trap Captures

Insects per trap
Jul 12 Jul 19 Jul 26
Codling moth  0.5 0.5 1.5
Oriental fruit moth 22.0 28.0 18.0
Tufted apple bud moth 0.0 0.0 1.0
Redbanded leafroller 1.0 0.0 0.0
Obliquebanded leafroller 0.0 0.0 3.0
Lesser appleworm n/a 0.0 0.0
Apple maggot (abandoned and research orchards) 0.0 0.0 0.0
Brown marmorated stink bug (commercial) 1.9 5.5 7.0
Brown marmorated stink bug (unsprayed) 0.5 2.1 5.0
Spotted tentiform leafminer 4.0 5.0 2.0
Dogwood borer 27.0 21.0 24.0
Peachtree borer 17.0 19.0 27.0
Lesser peachtree borer 14.0 17.0 13.0
San Jose scale 5.0 5.0 0.0

*Note that these averages illustrate only the timing of insect emergence and fluctuations in populations, and are not representative of population levels in any given orchard. The only way to have an accurate assessment of an individual orchard’s populations is to set up traps in that orchard.

2021 Accumulated Degree Days

Jul 13 Jul 19 Jul 26
Codling moth (Biofix: April 10)
1355 1512 1678
Oriental fruit moth (Biofix: March 27)
1885 2057 2279
Tufted apple bud moth (Biofix: April 30)
1527 1860 1920

About degree-day models

2021 Pest Trends (click to enlarge)

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Visit WNC Orchard Insect Populations for archived posts.

Additional Resources