Current Western NC Orchard Pest Populations Weekly Summary, June 29 2015

— Written By and last updated by

We track local insect populations throughout the growing season using a system of traps, temperature-recording devices, and degree-day models. Traps and weather data are checked weekly, with results updated by Tuesday afternoon from April through September. Learn more about southeastern apple pests at the Apple Pest Management page.

Weekly summary

JUNE 29, 2015

Checking traps in the orchard
We are currently in a period when there are relatively few insect pests that pose a threat to apples. Codling moth populations in lower elevation orchards, and, as discussed in last week’s pest news post, emergence of first generation  plum curculio may be a concern in orchards that experienced significant damage earlier in the season.

Codling Moth:  Depending on location, second generation codling moth is either in full flight or will be emerging in the next week. Insecticide sprays are based on degree-day accumulations, abundance of moths indicated by pheromone trap captures, and the level of damage caused by first generation larvae. Under very low population densities, usually when mating disruption is being used, no insecticide sprays may be necessary. Under high population densities, one or two well-timed applications are often necessary. See page 32 of the Apple IPM Guide to determine the need for second generation insecticide sprays. The choice of insecticide to use should be based on what was used to manage the first generation – choose an active ingredient effective against codling moth but not used against the first generation. For instance, Altacor (a.i.= chlorantraniliprole) and Delegate (a.i.= spinetoram) are two different insecticides commonly used for control of codling moth. In those orchards that sprayed Delegate during the first generation, Altacor should be applied during the second generation, or vice versa.

In higher elevation orchards in such as Henderson County, only about 1200 DD have accumulated since biofix, so in this area we are still at least 7 to 10 days from the beginning of moth emergence. In lower elevation orchards in the foothills and piedmont (e.g., Alexander, Wilkes, Cleveland, Lincoln and Polk Counties), codling moth degree-day accumulations range from about 1500 to 1650, which is equivalent to emergence of about 50 to 75% of second generation moths. Close attention should be paid to pheromone trap captures and an assessment of damage caused by first generation larvae.

In general, codling moth pressure has been fairly low this year, so in most situations a single insecticide application is provide sufficient control, but all decisions should be based on moth activity as measured by pheromone traps.

European Red MiteEuropean red mite still remains a threat in orchards that have not experienced problems as of yet. Typically, if ERM have not developed to problematic levels by the first week of July, populations will remain low for the remainder of the year in most instances – assuming that pyrethroid insecticides harmful to natural enemies are not used.

Average Weekly Trap Captures*

Insects per trap
June 15 June 22 June 29
Codling Moth 0.7 1.3 2.7
Oriental Fruit Moth 2.8 2.5 4.3
Tufted Apple Bud Moth 8.5 3.5 1.5
Redbanded Leafroller 0.0 0.0 0.5
Obliquebanded Leafroller 0.5 0.0 1.0
Lesser Appleworm 0.0 0.0 1.0
Apple Maggot 0.0 0.5 0.0
Brown Marmorated Stink Bug 0.3 1.5 0.8
Spotted Tentiform Leafminer 23.0 57.0 27.0
Dogwood Borer 38.0 59.0 84.0
Peachtree Borer 22.0 18.0 32.0
Lesser Peachtree Borer 53.5 42.0 31.0
San Jose Scale 0.0 1527.5 7675.0

*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.

Accumulated Degree Days

Henderson County
 Biofix June 15
June 22
June 29
Codling Moth April 23 828 1012 1176
Oriental Fruit Moth Apr 6 1330 1544 1771
Tufted Apple Bud Moth April 23 1070 1284 1476
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.

  • 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.

  • 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.

  • 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.