WNC Orchard Insect Populations for July 17, 2018

— Written By and last updated by

July 17, 2018Woolly apple aphid infestation

Codling moth degree day (DD) accumulations since biofix range from about 1660 in Henderson County to almost 2000 in Cleveland County, which coincides with second generation egg hatch of about 30% and 70% completion, respectively. In orchards not using mating disruption, an insecticide application effective against codling moth (Altacor or Delegate, whichever was NOT used against the first generation) should have been recently applied. Overall codling moth pressure has been fairly low in most orchards, so a single application is probably sufficient in many locations. If you are unsure of your population density, two applications at 14-day intervals are recommended. In orchards with very low codling moth pressure, as documented by low pheromone trap captures, other insecticides may also be considered, including Assail and Intrepid.

In orchards using mating disruption, insecticides targeting second generation codling moth are generally not needed unless pheromone trap captures indicate so – cumulative trap capture over successive weeks of >3 moths per trap.

Oriental fruit moth (OFM) populations are increasing across many locations. This is typical for this time of the year, and in the absence of mating disruption, populations often continue to rise into September. In past years monthly applications of sprayable OFM pheromone have been recommended to manage these late season surges, with the first application in late July to mid August, depending on population pressure. However, since the appearance of the BMSB and use of pyrethroids in August and September, OFM has become less of an issue, because pyrethroids used for BMSB are highly effective against OFM.

First generation brown marmorated stink bug (BMSB) adults are active in lower elevation orchards (<1500 ft elevation). Trap captures have been moderately high in Polk and Cleveland Counties, so a pyrethroid or neonicotinoid (Actara, Venom or Scorpion) may be necessary in these areas.

Woolly apple aphid infestation

Woolly apple aphid infestation

Woolly apple aphid parasite

Woolly apple aphid parasite

Parasitized woolly apple aphids

Parasitized woolly apple aphids

At higher elevations, such as Henderson County, first-generation adults have not yet emerged and pheromone trap captures remain very low. However, based on temperature forecasts and degree-day model predictions, the first adults are expected to begin emerging next week. To avoid early damage on highly susceptible varieties, such as Granny Smith, a BMSB spray (pyrethroid or neonicotinoid) should be considered at that time. The largest period of adult emergence, and greatest potential for damage, is not expected for another two weeks.

In recent years woolly apple aphid has become a more common occurrence throughout the region, likely due to increased pyrethroid use associated with BMSB. Now would be good time to begin scouting for this insect. There are very few insecticides with good knockdown activity; in fact Diazinon 50WP (the only formulation registered on apples) is perhaps the only dependable product for WAA at this time of the year. However, please note that it has a 4-day REI (re-entry interval) and a 21-day PHI (preharvest interval). A word of caution – predicting WAA population pressure based on last year’s situation is not a reliable system. WAA populations are known to fluctuate widely from year to year. High populations in one year often lead to high densities of the parasite Aphelinus mali, which can provide very effective biological control the following season. Hence, preventive insecticide applications are not recommended for this pest.


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


2018 Average Weekly Trap Captures*

HENDERSON COUNTY
Insects per trap
July 2
July 9
July 16
Codling Moth 0.3 1.0 4.8
Oriental Fruit Moth 15.7 11.0 34.0
Tufted Apple Bud Moth 0.0 0.0 1.0
Redbanded Leafroller 0.0 0.0 0.0
Obliquebanded Leafroller 0.0 0.0 0.0
Lesser Appleworm 0.0 0.0 0.0
Apple Maggot 0.0 0.0 0.0
Brown Marmorated Stink Bug (commercial – mountains) 0.3 0.2 0.5
Brown Marmorated Stink Bug (commercial – upper piedmont) 1.3 2.2 4.3
Brown Marmorated Stink Bug (research – unsprayed) 1.0 0.8 0.8
Spotted Tentiform Leafminer 0.0 0.0 0.0
Dogwood Borer 20.0 23.0 51.0
Peachtree Borer 30.0 37.0 37.5
Lesser Peachtree Borer 7.0 4.0 13.0
San Jose Scale 2.5 17.5 70.0

*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 3
July 10
July 17
Codling Moth Apr 30 1323 1488 1661
Oriental Fruit Moth Apr 2 1876 2071 2280
Tufted Apple Bud Moth May 4 1556 1752 1960
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.