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Management Options for Brown Marmorated Stink Bug in Pennsylvania Fruit Orchards - 2012 Perspective

Posted: May 29, 2012

The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Heteroptera-Pentatomidae) continues to dominate the list of potentially most damaging insect pests in Pennsylvania fruit orchards. Since the pest explosion during the 2010 season, this invasive exotic pest dictates most insect pest management activities in Pennsylvania orchards.
Dr. Greg Krawczyk and Dr. Larry A. Hull, Penn State Department of Entomology, Fruit Research and Extension Center, Biglerville, PA

 

Although our understanding of BMSB biology, behavior and ecology is gradually becoming more comprehensive, unfortunately we are still in the early stages of fully understanding its behavior in orchards and surrounding ecosystems.  Also, our current set of BMSB management recommendations although effective for most parts during the 2011 season, still have plenty of room for further improvement and refining. 

As we discovered last season, the practical results of available management options against BMSB populations can be quite challenging and sometimes even frustrating.  Despite using the best available practices within our IPM programs, utilizing the best recommended products and tactics, fruit injury levels in BMSB affected orchards ranged from almost not existing to well above acceptance levels for growers and costumers.  Last year articles in the May issue of Fruit Times and the April issue of Fruit Times provided our suggestions and recommendations based on the 2010 experience.
 
This update will concentrate on a few of the most important factors affecting management of brown marmorated stink bug following another year of experience dealing with this insect.

Factors Influencing the Management of BMSB

BMSB biology

Despite some observations of possible overwintering of BMSB adults in dead trees in the woods, it seems that most BMSB adults that infest orchards in the spring survive winter inside some kind of dwelling, and most of the time outside of orchards or other agricultural settings.  This spring (2012), we have observed adult BMSB coming out from houses and other structures starting in March, with the majority seeming to emerge very recently, in the second part of May.  In the spring, the BMSB adults appear to have no special preference for feeding on fruit, however during last week's observations we already found injured nectarines and peaches in orchards located close to buildings.  Later during the season, these differences in the initial food sources as well as diverse starting times for emergence of overwintering adults will create a situation that allows all BMSB nymphal and adult stages to be present in the orchard at the same time, without clearly defined generational structure, as we normally see with most other fruit pests.

BMSB movement

 Due to a wide range of available host plants for this pest in our region, it is important to remember BMSB can move to orchards at any time during the summer, from May until October, including multiple, consecutive influxes from surrounding vegetation such as agronomic crops (e.g., sweet corn or soybean) or woods.  Effective control of one wave of stink bugs in the orchard does not prevent another wave of BMSB from entering the orchard a short time later.  And since BMSB is not a resident pest in the orchard, even the best management activities against BMSB in the spring will not prevent new stink bugs from invading again later in the season, even in October. And while the detection of BMSB adults in the orchard does not always warrant an insecticide application, it is a good indicator of possible nymphal presence in the orchard.  And if BMSB nymphs are present, then treatment is almost always necessary.

Monitoring challenges

This year early season attempts for using various traps to monitor movement of BMSB adults into orchards again did not provide results we expected.  Although some low numbers of adult stink bugs were captured in the traps, the collections so far are not well correlated with the actual pressure observed during visual monitoring in the same orchard blocks. Results of last season's BMSB trapping observations suggest we can utilize commercially available traps (e.g., Dead–Inn traps from Ag-Bio, Inc. or Rescue SB traps from Sterling Int.) for BMSB detection in orchards, but only during late season (late July to September). Both mentioned traps were not effective in the early part of the season, when accurate detection of migrating adults could help to prevent an establishment of population within the protected area. We are continuing our BMSB monitoring research and hopefully will have better results to report as the season progresses. Unfortunately, with our current levels of understanding of BMSB biology and behavior, no specific thresholds are available that would correlate the number of observed BMSB and possible level of fruit injuries.  

Efficacy of insecticides

Laboratory and field evaluations of insecticides conducted during 2010 and 2011 demonstrated the availability of multiple highly effective active ingredients registered for use on fruit.  Laboratory bioassays performed by Penn State, USDA-ARS and Virginia Tech groups provide a nice complementary picture of what to expect from various insecticide products. The “Lethality index” developed by USDA researchers provides information on efficacy of products against adult BMSB after exposing them for 6 hours to a dry residue of insecticides, while the Penn State “Percent mortality” readings provide information on the toxicity of adult stink bugs after direct contact with 2 µl of an insecticide solution applied directly to the dorsal part of the insect abdomen (as it is happening during the actual spray in the orchard).  Both methods utilized long-term observations (up to 120 hours after treatment) to develop the final results.  To fill the gap in our understanding of the interaction between field insecticide residues and nymphs, during the late summer of 2011 we also conducted comprehensive evaluations of efficacy of field based dry residues of various compounds against second instar BMSB nymphs.  The results of both bioassays conducted at Penn State--direct adults (laboratory study) and field residual nymphs--are presented in Table 1.

Management of BMSB as Part of an IPM System - Experience from the 2011 Season

Despite all the publicity the stink bug challenge is gathering, other traditional fruit pests are still present in the system and need to be managed as well.  The simple presence of codling moth and/or oriental fruit moth larvae are still resulting in the rejection of fruit loads delivered to fruit processors (i.e., over a hundred rejections during the 2011 season), and external fruit injuries caused by leafrollers or plum curculio still downgrade the marketability of fresh fruit.  As part of our field research during 2011,  we evaluated the efficacy of various BMSB insecticide management programs in commercial fruit orchards. Tested programs, although directed and timed mostly against standard fruit pests such as codling moth, oriental fruit moth and leafrollers, within each application also included a product targeting BMSB.  Applications conducted during July and September had BMSB as the main pest target.  All evaluated products were tested at the rate effective against the targeted group of pests:  Altacor (rynaxypyr) at 3.0 oz/acre, Belay (clothianidin) at 6.0 oz/acre, Belt (flubendiamide) at 4.0 oz, Danitol (fenpropathrin) at 16.0 oz/acre, Delegate (spinetoram) at 4.5 to 5.0 oz/acre, Endigo (thiametoxam plus lambda-cyhalothrin) at 5.0 oz/acre, Lannate  LV (methomyl) at 2pt/acre, Lannate SP (methomyl) at 9.0 to 16 oz/acre, Scorpion (dinotefuran) at 8 to 12 oz/acre, and Voliam flexi (clorantraniliprole plus thiametoxam) at 7.0 oz/acre  The overall timings and programs are presented in Table 2. 

All programs provided excellent seasonal control of codling moth and Oriental fruit moth.  The control of the leafroller complex was also very effective during the season, except for the late season injury observed during the harvest evaluation. Dinotefuran, the active ingredient of Scorpion insecticide which was used for the late season BMSB applications, is not a highly effective product against this group of pests, and with relatively warm fall weather, the larval feeding of TABM and/or OBLR was not controlled effectively.

The late season applications of Scorpion were directed specifically against BMSB populations immigrating into orchards at that time of the season.  Despite targeted BMSB applications, the injury levels caused by this pest increased during harvest. With increased BMSB pressure originating outside of protected areas (e.g., in woods, soybean, other crops, etc.), and limited residual activity of dinotefuran against BMSB adults, it appears that utilized insecticide programs were not effective enough in preventing initial BMSB adult feeding on maturing fruit.  And as BMSB adults were trying to gather enough resources for the incoming overwintering period, each feeding attempt by BMSB was causing a detectable fruit injury.  Based on insecticide bioassays conducted last year we understand that, as direct contact activity of dinotefuran against BMSB adults is very high, the activity of field-aged residue is not effective enough to prevent the initial feeding.

Our attempts to evaluate alternative management options such as border sprays, ground cover applications, or controlling BMSB in surrounding field crops (e.g., soybean) did not generate conclusive results. The almost unrestricted movement of BMSB adults from one place to another greatly restricted the effects of such treatments and our ability to properly evaluate their direct effect.  While the results were very good in eliminating the BMSB nymphal populations from treated areas, the injuries caused by BMSB adults could not be prevented.

When developing a seasonal strategy to manage BMSB at any particular location, the following factors need to be considered during the stink bug management planning process:

  • Choice of insecticides:  use only the most effective products with the least negative impact on the beneficial insects in the orchard.  In order to reduce the number and amount of insecticides used in the orchard, consider the effect of BMSB-targeting products on other pests.
  • Sources of BMSB influx:  pressure from outside BMSB populations is not uniform within any particular orchard and it also fluctuates during various times of the season. And while not every BMSB adult warrants an insecticide treatment (as they can come and leave at any time), almost every nymph found feeding on trees is an indicator that treatments may be needed.
  • Characteristics of specific crop/block: .not all orchards or even blocks within a larger orchards will require identical intensive management options against BMSB.  Trees without fruit could still require insecticide treatments as they can still harbor BMSB populations.
  • Necessity of controlling other pests:  in selecting BMSB control options, growers should also consider other fruit pests and the beneficial natural enemies that may be affected by their selection of products used against BMSB.
  • Planning for a seasonal insect control program:  prepare ourselves for a season-long BMSB monitoring and management program.  The fact that BMSB is not present in the orchard during the early season does not provide any guarantee that possible late season BMSB infestation will not happen.

The brown marmorated stink bug is here and most likely will continue to seriously threaten our fruit system for a long time.  Over time, as we learn how to monitor and manage this pest more effectively, in a more sustainable fashion using tools such as insect behavior modifying materials (e.g., a sex pheromone, an attractant, repellent or deterrent) or natural enemies, our reliance on pesticides will likely be minimized.  In the meantime, with the knowledge we have and the tools that are available, we need to try to “outsmart” this pest in order to continue to produce the best quality fruit. As the 2012 growing season progresses and we continue the “learn as we go” approach, we will continue to provide the newest BMSB related information to growers as fast as possible.  So stay tuned to current updates and recommendations, which will be posted at the Penn State FREC web site as soon as they become available.

Table 1.  Efficacy of various insecticides against BMSB during direct contact laboratory bioassays (adults) and residual field bioassays (nymphs).  Penn State FREC 2012.

Active ingredient Product/rate tested % direct mortality adults @ 24 h* % residual mortality against nymphs @ 7 d*** Number of appl. /season **
acetamiprid- (IRAC 4A) Assail 6 oz 87 68 (8 oz rate) SF-4 app, PF-4 app
clothianidin- (IRAC 4A) Belay 6 oz 100 66 Peach -2 app, PF-2 app
imidacloprid- (IRAC 4A) Admire Pro 7oz 82 100 SF-1 app, PF-1 app
Leverage 360 2.8 oz (mix) 95 97 SF-1 app, PF-1 app
thiacloprid- (IRAC 4A) Calypso 8 fl oz 58 No data PF-2 app
thiamethoxam- (IRAC 4A) Actara 4.0 oz 92 100 SF-2 app, PF-3 app
Endigo 5 oz (mix) 98 100 SF-3 app, PF-4 app
Voliam Flexi 6 oz (mix) 100 No data SF-2 app, PF-2 app
methomyl- (IRAC 4A) Lannate SP 16 oz 92 84 Peach-6 app, nectarine-3 app, Apple-5 app
Lannate LV 3 pt 87 96 (2 pint rate) Peach-6 app, apple-5 app
Oxamyl-(IRAC 1A) Vydate 6 pt 68 No data Apple 1 app
fenpropathrin-(IRAC 3) Danitol 16 oz 95 100 SF-2 app, PF- 2 app
Lambda-cyhalothrin- (IRAC 3) Warrior II 2.5 oz 73 100 SF-4 app, PF-4app
Lambda-Cy 4.4 oz 52 No data SF-5 app, PF-5 app
Voliam Xpress 10 fl oz (mix) 40 No data SF-4 app, PF-4 app
Endigo 5 oz (mix) 98 100 SF-3 app, PF-4 app
endosulfan- (IRAC 2A) Thionex 2 lb 52 100 PF- 3 app, SF-2 app (until July 31, 2012)
bifenthrin-(IRAC 3) Bifenture 12.8 fl oz 100 100 Possible Section 18 registration (2012)
dinotefuran- (IRAC 4A) Scorpion 35 SL 5 oz 97 88 Possible Section 18 registration (2012)
Venom 3 oz 93 100 Possible Section 18 registration (2012)
* - dead and moribund BMSB adults grouped as dead, mortality at 24 h after exposure
** - SF- stone fruit, PF- pome fruit; Always read and follow the most current pesticide label.
*** - nymphal mortality after 24 h of exposure to foliage with 7 days old field aged residue of insecticide

Table 2. Examples of BMSB oriented insecticide programs tested during the 2011 season in three commercial apple orchards. Insecticide applications are listed as complete sprays, although most treatments were conducted as ARM applications. The exact dates of application and product choice/combination at each individual farm in some cases varied slightly from the spray matrix. Penn State FREC 2011.

Date DP program SV program GS program Target pests*
June 03 Altacor + Lannate Voliam flexi Delegate + Assail CM, LR, BMSB
June 15 Altacor + Lannate Voliam flexi Delegate + Warrior CM, LR, BMSB
July 01 Lannate Endigo Guthion BMSB, OFM
July 15 Lannate Endigo Actara BMSB, OFM
Aug 01 Belay Altacor + Lannate Belt + Lannate CM, LR, BMSB
Aug 15 Danitol Altacor + Lannate Altacor + Lannate CM, LR, OFM
Aug 30 Scorpion Scorpion Altacor + Lannate BMSB, CM, LR
Sep 15 Scorpion Scorpion Scorpion BMSB, OFM
CM- codling moth; LR – leafroller complex; OFM - oriental fruit moth; BMSB – brown marmorated stink bug