2022 Orchard Entomology Update: Mid to Late Summer Pests

In most Pennsylvania fruit orchards, mid to late July represents the last call to assess the results of insect pest management activities conducted earlier in the season and to make sure nothing important will be neglected for the remainder of the season. If something was missed, now it should be easy to spot injuries caused by codling moths (CM), Oriental fruit moths (OFM), or leafrollers such as tufted apple bud moths (TABM) and to a lesser degree, oblique banded leafroller (OBLR).

Based on moth captures in sex pheromone traps located in the Fruit Research and Extension Center orchards in Biglerville, PA, all four pest species started or are about to start their consecutive generations (second for CM, OBLR, and TABM, and third for OFM). See Flight Seasonalities of Main Fruit Pests During the Growing Season. If not controlled, each species can cause injuries at harvest. Based on the accumulation of developmental degree days for the codling moth, control of the second CM generation should be initiated about now.

The actual need for control will vary from orchard to orchard, and there is a chance in some orchards that no additional insecticides will be needed for the remainder of the season. However, some insect management will be necessary for most orchards. The captures of male moths in sex pheromone traps placed in orchards should help growers detect and decide “if” and eventually “when” treatment is needed. Properly maintained sex pheromone traps should provide answers about the actual pressure from various insect pests and help growers choose the best timing for management.

If insecticides are needed, products from IRAC Group 28 (ryanodine receptor modulators) such Altacor®, Exirel®, Minecto Pro®, Verdepryn ®, and Besiege® or a single product from the IRAC Group 5 Delegate® (nicotinic acetylholine receptor agonists; spinosyns) are highly active against CM, OFM, TABM and OBLR larvae. For the best results, insecticides used for managing CM and OFM must be applied before larvae enter the fruit, which usually happens less than 24 hours after the egg hatch.

Under normal weather conditions for southcentral PA, codling moth adults will continue to be active in orchards until mid-September and OFM until mid-October. Multiple applications of insecticides may be necessary to maintain an active insecticide residue on fruit and foliage. After larvae are already inside the fruit, no product will be able to control them. The injuries caused by codling moth larvae are characterized by older larvae feeding inside the fruit seed chamber, while most injuries caused by OFM larvae will be located either in the calyx or stem end of the fruit, and most of the feeding will be shallow under the fruit skin. Only leafroller control may be necessary for orchards using an effective CM and OFM mating disruption treatment. A product such as Intrepid ® (ecdysone receptor agonist, IRAC Group 18) will provide effective leafroller control. In orchards managed with products approved for organic production, applications of codling moth granulosis virus (Madex® HP or Cyd-X®) should start at the beginning of moth flight and be repeated at intervals no longer than seven days. Madex HP should also provide good control of Oriental fruit moth larvae. Leafrollers can also be managed by applications of products containing Bacillus thuringiensis (Dipel®) or spinosyns (Entrust®).

Photo 1. (left) Codling moth males inside pheromone trap, (center) early symptoms of CM on apple fruit, (right) codling moth and oriental fruit moth adult moths side by side. Photos: G. Krawczyk, Penn State

Brown marmorated stink bug update

Usually, late July and early August mark the start of more intensive BMSB movement into orchards and increased fruit damage. Commercially available BMSB traps and lures utilizing an aggregation pheromone are very helpful in BMSB detection. Commercial BMSB lures and traps are available from Ag-Bio Inc., Phone: 877-268-2020 or Trece Inc., Phone: 866-785-3063.

BMSB monitoring traps should be placed at the border of the woods or under trees in the first row in the orchard. At least a single additional trap should also be placed somewhere in the middle of the orchard block to monitor potential pressure from BMSB populations established by adults bypassing the border of the orchard and flying deeper into the orchard. For the best results, Ag-Bio Dead-In pyramid traps or Trece Stink Bug STKY^TM Dual Panel Adhesive Traps should be placed on the ground under the trees. While BMSB nymphal feeding can be effectively reduced by well-timed insecticide treatments (BMSB nymphs are so-called “resident” pests), feeding on fruit by wandering BMSB adults is more difficult to prevent. At this time, BMSB pressure from resident BMSB populations in the majority of orchards should still be low, and pressure from BMSB adults established outside of the orchards represents a continuous challenge.

With all “traditional pests” potentially present in the orchard, it is particularly important that the choice of insecticides directed against other pests will also consider the possible control of BMSB populations present in orchards at the time of application. The list of BMSB effective insecticides options includes products with only a few distinctive modes of action: pyrethroids (IRAC Group 3A) such as Danitol®, and Warrior®; neonicotinoids (IRAC Group 4A) such as Actara®, Assail ®, Belay®; one carbamate product (IRAC Group 1A), Lannate and some products including combinations of two different insecticide chemistries such as in Endigo® or Leverage®. Neonicotinoids with active ingredient dinotefuran, such as Venom and Scorpion, are also legal for use on peaches and nectarines with a 3-day pre-harvest interval (PHI); however, the currently registered rates are not effective against BMSB.

With about ten more weeks of possible BMSB activity this season (until mid-October on late-maturing apple varieties), it is extremely important that growers plan ahead with a variety of products utilized against BMSB, and preserve the most effective products, especially with the shortest PHI, for applications when the pressure from this pest is expected to increase in late August and September. Management activities against BMSB should also be effective against other native stink bugs moving into orchards during the fall.

Photo 2. (left) Brown marmorated stink bug fresh egg mass and adult, (center)) BMSB nymph and adult on apple, and (right) green stink bug and BMSB nymphs. Photos: G. Krawczyk, Penn State

Woolly apple aphid (WAA) colonies are being observed in some orchards across the region. Most WAA colonies start around wounds or leaf petioles and continue to increase and move as the season progresses. Tiny parasitic wasps (Aphelinus mali) and syrphid flies (Heringia calcarata and Eupeodes americana) that parasitize larvae are highly effective natural control of WAA colonies. Unfortunately, beneficial insects are also very sensitive to many synthetic pesticides, and natural control of WAA can easily be disrupted by using pyrethroid and/or neonicotinoid insecticides applied to manage other pests such as brown marmorated stink bug or leafhoppers. If WAA control is needed, the most effective products are Diazinon® (various formulations) and Movento®. Only a single application of products containing diazinon is allowed after apple bloom. If applied correctly, both products should also help manage the summer generation of San Jose scale crawlers.

Photo 3. (left) Woolly apple aphid early stage of tree infestation, (center) severe infestation of apple trees by WAA, and (right) WAA colony partially parasitized. Photos: G. Krawczyk, Penm State

Japanese beetles (JB) are present in many orchards. Emerging adults aggregate on various plants, including all fruit trees, and feed on the foliage (Photo 4). Neonicotinoid insecticides such as Assail, Admire Pro, Belay, and pyrethroids such as Danitol, Warrior, or Asana are very effective in controlling JB, although multiple applications of insecticides may be needed as new individuals continue to arrive from outside sources. Management of JB with neonicotinoid insecticides will also provide good control of aphids or leafhoppers. Most materials recommended for controlling brown marmorated stink bug should also provide good control of JB.

Photo 4. Japanese beetle adults feeding on grape foliage and nectarine fruit. Photos: G. Krawczyk, Penn State

And please remember, the distribution of most mid-summer pests tends to be highly localized, and the actual management may be justified only in some isolated orchards or even in only parts of the blocks.