WNC Orchard Insect Populations for August 7, 2018

— Written By and last updated by

ARainy apple orchardugust 7, 2018

Overall, insect populations are fairly low at this time, which is probably in part due to the heavy rains. Second generation codling moth flight is complete and trap captures are low throughout the region. While OFM populations can increase during the next several weeks, those numbers have also been quite low to date.

The two main insects of concern remain brown marmorated stink bug and apple maggot. First generation adult BMSB will continue to emerge over the next several weeks, but to date numbers have been fairly low. Apple maggot captures have been high for the past three weeks, and orchards near abandoned sites are at greatest risk. In those orchards where apple maggot is a potential concern, particularly with ‘Golden Delicious,’ and pyrethroids are not being applied for BMSB, imidacloprid should be considered.

In areas with heavy hail damage and where apples are destined for processing or juice, some thought should go into whether or not it is economically wise to apply pyrethroids for BMSB control. These apples already have damage similar to stink bug, and it is doubtful that spraying for BMSB will increase the value of the fruit. In addition, avoiding pyrethroid applications this year should help natural enemy populations return to pre-2017 levels, and reduce the potential for European red mite, woolly apple, and San Jose scale outbreaks next year. Just some food for thought.


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


2018 Average Weekly Trap Captures*

HENDERSON COUNTY
Insects per trap
July 23
July 30
August 6
Codling Moth 2.5 1.5 0.5
Oriental Fruit Moth 23.0 17.7 13.0
Tufted Apple Bud Moth 6.0 3.0 1.0
Redbanded Leafroller 0.0 0.0 0.0
Obliquebanded Leafroller 1.0 2.0 1.0
Lesser Appleworm 2.0 5.0 1.0
Apple Maggot (abandoned and research) 7.7 19.3 21.3
Brown Marmorated Stink Bug (commercial – mountains) 0.7 0.8 1.0
Brown Marmorated Stink Bug (commercial – upper piedmont) 2.8 2.2 1.8
Brown Marmorated Stink Bug (research – unsprayed) 0.5 1.8 1.3
Spotted Tentiform Leafminer 14.0 5.0 3.0
Dogwood Borer 4.0 60.0 19.0
Peachtree Borer 65.0 29.5 22.5
Lesser Peachtree Borer 10.0 10.5 10.5
San Jose Scale 0.0 2.5 5.0

*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 July 24
July 30
August 7
Codling Moth Apr 30 1819 1950 2100
Oriental Fruit Moth Apr 2 2473 2633 2819
Tufted Apple Bud Moth May 4 2154 2314 2500
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.

2018 Pest Trends (click to enlarge)

codling moth population trend graph oriental fruit moth population trend graph tufted apple bud moth population trend graph redbanded leafroller population trend graph lesser appleworm population trend graph obliquebanded leafroller population trend graph spotted tentiform leafminer population trend graph dogwood borer population trend graph peachtree borer population trend graph lesser peachtree borer population trend graph apple maggot population trend graph brown marmorated stink bug population trend graph san jose scale population trend graph

Written By

Photo of Jim Walgenbach, N.C. Cooperative ExtensionDr. Jim WalgenbachExtension Entomology Specialist (Fruits / Vegetables) (828) 687-0570 (Office) jim_walgenbach@ncsu.eduEntomology & Plant Pathology - NC State University
Updated on Aug 7, 2018
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