WNC Orchard Insect Pest Populations – September 8, 2020

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Brown marmorated stink bugs on trapWith apple harvest well underway, and most pests other than the brown marmorated stink bug declining in numbers; this will be the last Pest Update for 2020.

First-generation BMSB adults continue to emerge across the region, with about 90% of the population having emerged in Lincoln County, but only about 25% emergence complete in Haywood County (see Fig. 1 below). Estimated emergence in Henderson and Wilkes County is 45 and 62% complete, respectively. Pheromone trap captures continue to increase in Henderson County (see Fig. 2 below). With first-generation adult emergence continuing for the next several weeks, expect trap captures to continue to increase. In 2018 and 2019, BMSB trap captures peaked about this time, but we are currently about 200 DD behind where we were at this time in previous years.

Figure 1: Percent emergence of brown marmorated stink bug in 2020. Figure 2: Brown marmorated stink bug trap captures in 2020 versus 2019 and 2018

It should be noted that BMSB pheromone trap captures are considerably lower in commercial apple orchards compared to non-orchard sites or orchards at the research station. Mean trap captures last week averaged about 5 and 32 per trap in commercial orchards and other sites, respectively. Nonetheless, with adult activity expected to continue for the next month, protection of highly susceptible cultivars (i.e., Granny Smith, Pink Lady) should be considered.

The only two other insect pests of potential concern are the oriental fruit moth and apple maggot, both of which exhibited declining trap captures during the past week. It is not typical for these pests to develop for the first time this late in the season, so the threat of damage should be considered very low for the remainder of the season.

While this is the last written report of the season, insect population tables and graphs will continue to be updated through the end of the month. Also, if something unexpected occurs, we will send a pest alert update.

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

2020 Average Weekly Trap Captures

Insects per trap
Aug 24 Aug 31 Sep 7
Codling moth  0.0 0.1 0.0
Oriental fruit moth 6.7 4.3 2.6
Tufted apple bud moth 5.0 0.5 0.0
Redbanded leafroller 0.0 0.0 0.0
Obliquebanded leafroller 0.0 0.0 0.0
Lesser appleworm 2.0 0.0 0.0
Apple maggot (abandoned and research orchards) 1.7 7.0 2.3
Brown marmorated stink bug (commercial) 2.4 3.7 7.3
Brown marmorated stink bug (unsprayed) 11.3 23.5 31.8
Spotted tentiform leafminer 0.0 0.0 0.0
Dogwood borer 20.0 27.0 13.0
Peachtree borer 30.0 18.0 14.0
Lesser peachtree borer 40.0 38.0 33.0
San Jose scale 260.0 225.0 35.0

*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.

2020 Accumulated Degree Days

Aug 24 Aug 31 Sep 7
Codling moth (Biofix 4/20) 2216 DD 2405 DD 2567 DD
Oriental fruit moth (Biofix 3/30) 2994 DD 3223 DD 3417 DD
Tufted apple bud moth (Biofix 4/27) 2736 DD 2965 DD 3159 DD

About degree-day models

2020 Pest Trends (Click to Enlarge)

Graph of insect population trendsGraph of insect population trendsGraph of insect population trendsGraph of insect population trendsGraph of insect population trendsGraph of insect population trendsGraph of insect population trendsGraph of insect population trendsGraph of insect population trendsGraph of insect population trendsGraph of insect population trendsGraph of insect population trendsGraph of insect population trends

Visit WNC Orchard Insect Populations for archived posts.

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