WNC Orchard Insect Pest Populations – September 7, 2023
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With apple harvest fully underway, this will be the last insect update of 2023.
During the past 7 to 8 years, brown marmorated stink bug (BMSB) has been the major late-season insect pest of apples. While increased use of pyrethroid insecticides in August and September to control BMSB has been moderately successful in minimizing damage to apples, it has led to problems with some secondary pests. Specifically, pyrethroids have contributed to increased populations of European red mite and San Jose scale.
BMSB populations this year are the lowest we have observed in August and September for at least the last 5 years. Below is a figure showing weekly captures of BMSB in pheromone traps since 2019. Trends show a definite decline in populations during the past two years. Along with this decline in 2022 and this year, it appears that overall damage is also decreasing. Damage to apples was very high in 2021, when populations were at their highest. In contrast, damage in commercial orchards last year (2022) was low, a year when BMSB populations were considerably lower than in previous years. Although we still have several weeks to go before the full picture is drawn for 2023, early assessments suggest overall low damage up to this point in time.
Whether or not declining BMSB populations are a trend that will continue into future years is obviously unknown at this time. But hopefully they are on a permanent decline in NC, and we can return to a less aggressive pesticide program that will be more compatible with biological control of European red mites and San Jose scale.
Learn more about southeastern apple insect pests at the Apple Insect Management page.
2023 Average Weekly Trap Captures
|Insects per trap|
|Aug 21||Aug 28||Sep 5|
|Oriental fruit moth||31.5||48.0||57.0|
|Tufted apple bud moth||2.0||0.0||0.0|
|Apple maggot (abandoned and research orchards)||3.7||3.7||1.0|
|Brown marmorated stink bug (commercial)||1.9||2.1||1.5|
|Brown marmorated stink bug (unsprayed)||3.0||7.0||8.3|
|Spotted tentiform leafminer||0.0||0.0||0.0|
|Lesser peachtree borer||4.0||5.5||4.5|
|San Jose scale||37.5||2.5||162.5|
*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.
2023 Accumulated Degree Days
|Aug 21||Aug 28||Sep 5|
|Codling moth (Biofix: April 7)||2249||2450||2618|
|Oriental fruit moth (Biofix: March 24)||3054||3295||3503|
|Tufted apple bud moth (Biofix: April 21)||2701||2942||3150|