WNC Orchard Insect Populations for April 15, 2021

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Petal Fall Spray Options

Apple blooms at edge of orchardWith petal fall spray imminent in most locations, insecticide options will depend on what was applied before bloom and whether or not OFM mating disruption is being used. Another consideration is the level of bee activity in an orchard. For insecticides toxic to bees, which include many recommended at petal fall, it is important that bees are removed from orchards before sprays are applied.

The key insect pests to target at petal fall include plum curculio, oriental fruit moth and rosy apple aphid. Among these insects, the plum curculio presents the greatest threat, because petal fall is essentially the only time that it can be effectively controlled, while other options are available for OFM and rosy apple aphid.

Plum Curculio: This remains one of the most common causes of insect damage to apples in this region, and effective control is highly correlated with petal fall sprays. Although the severity of damage varies considerably among orchards, plum curculio is ubiquitous and can cause damage in virtually every orchard. In orchards with a history of problems, sprays should be made as quickly after petal fall as possible. In orchards where damage is historically low, there is usually a longer buffer period and sprays can be slightly delayed. However, 1st Cover is often too long to wait.

Rosy Apple Aphid:  Rosy apple aphid is a sporadic pest, but it can be difficult to monitor, and control with curative applications of insecticides can be difficult. Most neonicotinoids and closely related insecticides are effective against RAA, and effective control can be achieved before bloom at Pink, or after bloom at petal fall.

Oriental Fruit Moth:  Biofix at the research station in Henderson County was set on 27 March (codling moth biofix was 9 April). In orchards using mating disruption for OFM, insecticidal control of the first generation is not necessary, so focus on plum curculio and rosy apple aphid if relevant. However, where mating disruption is not used, an insecticide effective against this pest is recommended to control the first generation.

Insecticide Options:  Because of the importance of plum curculio, only those insecticides with activity against this pest are recommended at petal fall.

Relative Efficacy Chart for Petal Fall Insecticide Options

(― = No activity; P = poor; F= Fair; G = Good, E = excellent)
Insecticide Plum curculio OFM RAA Toxicity to bees
Actara E F E Highly toxic
Assail F G E Mod. toxic
Avaunt G G Mod. toxic
Imidan E E Mod. toxic
Verdepryn G E Highly toxic
Voliam Flexi* E E E Highly toxic
*Voliam Flexi is a premix that includes thiamethoxam (a.i. in Actara) and chlorantraniliprole (a.i. in Altacor).

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

2021 Average Weekly Trap Captures

Insects per trap
Mar 30 Apr 5 Apr 12
Codling moth  setup 0.0 2.0
Oriental fruit moth 17.5 12.0 50.0
Tufted apple bud moth setup 0.0 0.0
Redbanded leafroller 10.0 9.0 7.0
Obliquebanded leafroller
Lesser appleworm
Apple maggot (abandoned and research orchards)
Brown marmorated stink bug (commercial)
Brown marmorated stink bug (unsprayed) 0.0 0.0 0.0
Spotted tentiform leafminer 0.0 4.0 0.0
Dogwood borer setup 0.0 0.0
Peachtree borer setup 0.0 0.0
Lesser peachtree borer setup 0.0 1.0
San Jose scale 0.0 0.0 0.0

*Note that these averages illustrate only the timing of insect emergence and fluctuations in populations, and are not representative of population levels in any given orchard. The only way to have an accurate assessment of an individual orchard’s populations is to set up traps in that orchard.

2021 Accumulated Degree Days

Mar 30 Apr 5 Apr 12
Codling moth (Biofix: April 9)
Oriental fruit moth (Biofix: March 27)
27 56 152
Tufted apple bud moth (Biofix has not been established)

About degree-day models

2021 Pest Trends (click to enlarge)

Graph of insect population trends Graph of insect population trends Graph of insect population trends Graph of insect population trends Graph of insect population trends Graph of insect population trends Graph of insect population trends Graph of insect population trends Graph of insect population trends Graph of insect population trends Graph of insect population trends Graph of insect population trends Graph of insect population trends