WNC Orchard Insect Populations for July 31, 2018

— Written By and last updated by

July 31, 2018

Three key insect pests are of concern at this time, including codling moth (whose populations are declining), brown marmorated stink bug, and apple maggot.

With codling moth degree day (DD) accumulations ranging from about 1975 in Henderson County to 2350 in Lincoln County, we are nearing the end of second generation flight throughout the region. Pheromone trap captures have been relatively low in the majority of orchards, but there are orchards that continue to have high trap captures and insecticides effective against this pest should continue to be applied.

First generation brown marmorated stink bug emergence is picking up steam at this time. In higher elevation orchards (about 2000 ft), pheromone trap captures have increased during each of the past two weeks, and the major emergence is expected to occur in the second to third week of August. BMSB control in these areas will be particularly important from mid-August to mid-September.

Off the mountain in Burke and Lincoln Counties, first generation adult emergence has been underway for the past several weeks. Overall numbers have been relatively low in our sample sites, but the threat of damage is expected to continue through the end of August.

Finally, apple maggot trap captures have been very high for each of the past two weeks. While orchards near non-sprayed orchards are at greatest risk, this insect often appears in orchards far from abandoned sites. Hence, if not trapping in individual orchards, one should assume a high risk for this pest.

Pyrethroid insecticides are commonly used at this time for BMSB control, and will also protect crops against apple maggot and oriental fruit moth. However, pyrethroids are generally weak against codling moth, so in those orchards with codling moth problems, the addition of Altacor or Delegate (whichever was not used against the first generation) should be considered. There are several premixes that include group 28 insecticides (active ingredients in Altacor and Exirel) with either lambda-cyhalothrin (Besiege – 14 day PHI) or thiamethoxam (Voliam Flexi – 35 day PHI) that are options for control of both codling moth and BMSB in those orchards that did not use Altacor during the first codling moth generation.


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


2018 Average Weekly Trap Captures*

HENDERSON COUNTY
Insects per trap
July 16
July 23
July 30
Codling Moth
4.8
2.5
1.5
Oriental Fruit Moth
34.0
23.0
17.7
Tufted Apple Bud Moth
1.0
6.0
3.0
Redbanded Leafroller
0.0
0.0
0.0
Obliquebanded Leafroller
0.0
1.0
2.0
Lesser Appleworm
0.0
2.0
5.0
Apple Maggot
0.0
7.7
19.3
Brown Marmorated Stink Bug (commercial – mountains)
0.5
0.7
0.8
Brown Marmorated Stink Bug (commercial – upper piedmont)
4.3
2.8
2.2
Brown Marmorated Stink Bug (research – unsprayed)
0.8
0.5
1.8
Spotted Tentiform Leafminer
0.0
14.0
5.0
Dogwood Borer
51.0
4.0
60.0
Peachtree Borer
37.5
65.0
29.5
Lesser Peachtree Borer
13.0
10.0
10.5
San Jose Scale
70.
0.0
2.5
*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
July 17
July 24
July 30
Codling Moth
Apr 30
1661
1819
1950
Oriental Fruit Moth
Apr 2
2280
2473
2633
Tufted Apple Bud Moth
May 4
1960
2154
2314

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 graphOriental fruit moth population trend graphTufted apple bud moth population trend graphRedbanded leafroller population trend graphLesser appleworm population trend graphSpotted tentiform leafminer population trend graphObliquebanded leafroller population trend graphPeachtree borer population trend graphDogwood borer population trend graphLesser peachtree borer population trend graphApple maggot population trend graphBrown marmorated stink bug population trend graphSan Jose scale population trend graph