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Pressure from Stink Bugs Continues in Apple Orchards

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Posted: August 22, 2013

With the growing season winding down and most of our traditional fruit pests well under control and not present in orchards, the brown marmorated stink bug (BMSB) continues to represent the most important threat to our apple crop.
BMSB late instar nymphs (left) and adult (right). Photos by Greg Krawczyk, Penn State FREC, 2013.

BMSB late instar nymphs (left) and adult (right). Photos by Greg Krawczyk, Penn State FREC, 2013.

The incessant feeding of growing nymphs (we are finding all BMSB instars during our observations) and summer adults poses a significant economic risk to maturing fruit as each probing or feeding by BMSB on apples eventually results in a visible injury.

A single BMSB adult or nymph in the orchard can potentially cause injury to many fruit. Another complicating element is the fact that fresh injuries from stink bug feeding are initially almost undetectable, but after only a few days, the injury can become very apparent. Since the actual feeding occurs under the skin of the fruit, it is only after the affected cells start dying that the symptoms of feeding (i.e., corking) become visible. Also, since no fungal pathogens are transmitted during BMSB feeding, the affected area remains dry and no decay is observed. If BMSB feeding occurs just prior to harvest, it is quite possible that affected fruit will exhibit no visible signs of injury, but the characteristic depression on the fruit surface will develop after a period of time in storage.

Based on our experience from the last three seasons, we expect BMSB feeding will continue at least until mid-October. BMSB adults will continue feeding as long as weather permits or until they begin moving towards their overwintering sites. During the 2012 season we still collected BMSB adults in traps located in orchards in early November. Late season feeding can be very intensive, as adult stink bugs are trying to accumulate enough resources to survive the winter. While the BMSB adults are in their overwintering shelters, they do not feed so all resources need to be gathered before moving into their shelters.

Monitoring for the BMSB still remains an area that requires a lot of attention. While the currently used trapping systems have been effective in capturing both adult and nymph stink bugs over the past few weeks, there are still a lot of gaps in our understanding on how to interpret these findings. The aggregation pheromone currently utilized in traps appears to attract a higher number of individuals than the traps are capable of capturing. However, if detection of the stink bug is the goal of the monitoring activities, then these traps should be able to serve this purpose.

Fortunately, not every orchard will experience the same high pressure from the BMSB. Based on our current observations (through late August), the highest numbers of BMSB were observed on the edges of orchards bordering with woods or various agronomic crops, although not every soybean/corn field has high populations. But definitively, cautious scouting and monitoring of the vegetation surrounding an orchard should be very helpful in deciding if any special stink bug control treatment(s) is necessary. It is important to remember that the absence of stink bugs during the season does not guarantee that they will not become abundant in the orchard just before harvest. BMSB is not an orchard resident pest and management tactics utilized to control BMSB during the season in any particular block cannot guarantee or prevent new individuals from infesting/re-infesting the site just prior to harvest.

In order to manage possible infestations, a careful monitoring program needs to be employed. If stink bugs or injured fruit are detected, then the decision will have to be made about the best approach to manage the problem. Insecticides still remain the only effective BMSB management tool, but none of them will protect fruit from some level of damage. Early detection of feeding BMSB will help to limit the damage but not eliminate it completely. The most effective products will control only the individuals present in the orchard at the time of the application (i.e., direct contact activity), but they will not stop newcomer BMSB adults from at least initially probing the fruit. Remember that each probing equals an injury. Most of the effective insecticides provide only a few days of residual protection. The results of our recently conducted residual bioassays reveal that most of the recommended insecticides provide sufficient residual control of BMSB nymphs for at least 7 or even 12 days after the application (higher rates of product usually provide longer residual activity).

The following list includes insecticides with significant activity against BMSB adults and nymphs, as well as the pre-harvest (PHI) information for each product. The BMSB adult efficacy rating is based both on our earlier laboratory bioassay results conducted last winter and those conducted during this season. 

  • Acetamiprid (IRAC Group 4A) (Assail 30 SG): 7 day PHI on pome and stone fruit. No more than 32.0 oz of formulated product per acre per season. BMSB adult direct contact mortality at 72 hours - about 87%.
  • Bifenthrin (IRAC Group 3) (Brigade WSB, Bifenture EC, Bifenture 10DF; products registered under Special Section 18 Emergency Exception Registration for 2013 season): 14 day PHI on apples, peaches and nectarines. Maintain at least 30 day interval between consecutive applications. BMSB adults direct contact mortality and BMSB nymphs residual mortality (at 7 days) - 100%.
  • Clothianidin (IRAC Group 4A) (Belay): 7 day PHI on apples and pears; 21 day PHI on peach. No more than 0.2 lb AI per acre per season allowed. BMSB adult direct contact mortality at 72 hours - 100%.
  • Dinotefuran (IRAC Group 4A) (Scorpion, Venom, Special Section 18 emergency registration until Oct 15, 2013): 3 day PHI on pome and stone fruit. No more than 2 applications of this active ingredient per season. BMSB adult direct contact mortality at 72 hours - about 98%.
  • Fenpropathrin (IRAC Group 3) (Danitol): 14 day PHI on apples and pears; 3 days on stone fruit.  No more than 0.8 pound of AI allowed per acre per season. BMSB adult direct contact mortality at 72 hours - about 82%.
  • Imidacloprid (IRAC Group 4A) (Admire Pro, Leverage (imidacloprid mix with beta-cyfluthrin)): Admire Pro has 7 day PHI on pome fruit; 0 days PHI on stone fruit. No more than 0.5 lb AI per season. Leverage SC 360 has 7 day PHI on pome and stone fruit. No more than 0.044 lb AI per acre of beta-cyfluthrin and/or 0.088 lb AI per acre of imidacloprid. Admire Pro BMSB adult direct contact mortality at 72 hours - about 87%; Leverage BMSB adult direct contact mortality at 72 hours - about 93%.
  • Lambda-cyhalothrin (IRAC Group3) (Warrior II with Zeon Technology, Taiga Z): 21 day PHI on pome fruit; 14 day PHI on stone fruit. BMSB adult direct contact mortality at 72 hours - about 72%.
  • Methomyl (IRAC Group 1A)(Lannate): 14 day PHI on apples; 7 days on pears; 4 days on peaches; 1 day on nectarines (PA only). On apples no more than 4.5 pounds of AI per acre is allowed; on peaches no more than 5.4 pounds of AI per acre per season; on pears no more than 1.8 pounds of AI per acre per season. BMSB adult direct contact mortality at 72 hours - about 90%.
  • Thiametoxam (IRAC Group 4A) (Actara, Endigo (thiametoxam mix with lambda-cyhalothrin)): 35 day PHI for both products on pome fruit; 14 day PHI on stone fruit. No more than 0.2 lb AI lambda-cyhalothrin containing products or 0.172 lb AI (stone fruit) or 0.258 lb AI (pome fruit) of thiametoxm containing products per season. For Actara the BMSB adult direct contact mortality at 72 hours - about 95%; for Endigo the BMSB adult direct contact mortality at 72 hours - 100%.

Always read the most current pesticide label before applying any pesticide.

Contact Information

Grzegorz (Greg) Krawczyk
  • Extension Tree Fruit Entomologist
Email:
Phone: 717-677-6116