WNC Orchard Insect Populations for September 11, 2018

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September 11, 2018

apples on tree
As mid-September approaches, populations of most insect pests are on the decline. Codling moth, oriental fruit moth, and apple maggot are no longer of concern in >99% of orchards. While brown marmorated stink bug adults are still active, they too will soon begin to decline as they disperse to overwintering sites in the next 7 to 10 days. Overall, BMSB damage has been quite low, and averages less than 2% across more than 20 orchards sampled during the past week. The fact that overall damage did not appreciably increase since the last damage estimates in mid-August suggests that within-orchard populations are very low and the potential for further damage is also low. The expected rains associated with Hurricane Florence will further suppress BMSB activity.

Unless something unusual in the insect world occurs in the next couple of weeks, this will be the last Insect Update for 2018.

HOWEVER, if anyone comes across large numbers of BMSB adults congregating on homes, sheds, or vehicles in the coming weeks, or if you hear about large numbers of bugs occurring somewhere else, please get in contact with either Jim (828-684-3562)  or Steve (828-713-4000). By large numbers, we’re talking about hundreds to thousands. We’re always looking for good collection sites, and willing to travel on short notice to collect.

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

2018 Average Weekly Trap Captures*

HENDERSON COUNTY
Insects per trap
Aug 27
 Sep 5
 Sep 10
Codling Moth 0.0 0.8 0.0
Oriental Fruit Moth 29.0 40.0 15.0
Tufted Apple Bud Moth 0.0 0.0 0.0
Redbanded Leafroller 1.0 0.0 0.0
Obliquebanded Leafroller 1.0 0.0 0.0
Lesser Appleworm 0.0 0.0 1.0
Apple Maggot (abandoned and research) 4.0 1.0 0.5
Brown Marmorated Stink Bug (commercial – mountains) 2.2 4.2 2.2
Brown Marmorated Stink Bug (commercial – upper piedmont) 3.3 5.9 4.7
Brown Marmorated Stink Bug (research – unsprayed) 8.4 14.0 14.5
Spotted Tentiform Leafminer 0.0 0.0 0.0
Dogwood Borer 42.0 13.0 7.0
Peachtree Borer 27.0 28.5 4.5
Lesser Peachtree Borer 37.0 57.5 8.5
San Jose Scale 212.5 540.0 212.5

*Note that averages presented here are intended only to illustrate the timing of insect emergence and fluctuations in population activity, and not as general indicators of population levels. Some orchards included in these averages have significantly higher or lower populations than most commercial orchards in the area, resulting in averages that are sometimes skewed from what is typical. The only way to have an accurate assessment of an individual orchard’s populations is to set up traps in that orchard.

2018 Accumulated Degree Days

  Henderson County
 Biofix Aug 28
 Sep 6
 Sep 11
Codling Moth Apr 30 2595 2844 2942
Oriental Fruit Moth Apr 2 3424 3723 3841
Tufted Apple Bud Moth May 4 3105 3404 3522

About degree-day models:

The degree day (DD) models predict adult emergence and egg hatch of each generation. They do not predict the intensity of populations, which can be assessed by using pheromone traps. Hence, the models should be used to help gauge the time period when control is most likely needed, and pheromone traps provide information on the need for and frequency of insecticide applications. For full details, read “IPM Practices for Selected Pests” in the Orchard Management Guide.

CODLING MOTH:

  • 1st generation: Egg hatch begins at about 350 DD after biofix and is completed by 1050 DD. The most critical period for insecticidal control is from 350 to about 750 DD.
  • 2nd generation: Egg hatch of the second generation can extend from about 1300 to 2600 DD after biofix, but the most critical period for insecticidal control is 1400 to about 2500 DD.
  • 3rd generation: Adults begin to emerge at about 2500 DD after biofix, but the model is less accurate in predicting late-season populations.

ORIENTAL FRUIT MOTH:

  • 1st generation: Only one insecticide application between 400 and 500 degree days is usually necessary, as 1st generation egg-laying is usually low on apple.
  • 2nd generation: Effective 1st-generation control may eliminate the need for 2nd-generation control. If trap captures remain high, insecticides may be needed around 1100 to 1400 DD.
  • 3rd generation: Insecticide may be needed at 2200 DD after biofix.
  • 4th generation: Overlapping generations late in the season make it difficult to predict when 4th-generation egg hatch begins, but continuous egg-laying can occur from August through October. Use traps to determine the need for further insecticide applications.

 TUFTED APPLE BUD MOTH:

  • 1st generation: One well-timed insecticide application between 800 and 1200 DD after biofix will often eliminate the need for further control of TABM.
  • 2nd generation: Only if trap captures exceed 25 moths per trap by 2600 DD is an insecticide application recommended. NOTE: Insecticides targeting 2nd generation TABM are usually not necessary if 1st generation populations were successfully controlled.

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