Black Stem Borer: Old Pest, But New Problem For New York Apple Growers [Slideshow]

The black stem borer (BSB) is not a new pest in the U.S. however, we first detected black stem borer in 2013 in six sites in the Lake Ontario fruit region of New York, and have identified at least eight more sites this year. These beetles have killed large numbers of apple trees in western New York.

The BSB was introduced from Eastern Asia and first detected in New York in 1932. It has since been detected in most parts of the U.S. It is a general wood boring insect, in the group called Ambrosia beetles, with a huge list of suitable hosts including American beech, maple, dogwood, black walnut, oak, magnolia, and several other ornamental and forest species. It was also documented in apple and sweet cherry in 1982.

How They Infest Trees
The tiny black beetles overwinter in galleries at the base of infested trees. The first beetles emerge from overwintering sites to infest new sites after two to three days with temperatures of at least 68°F. This means they can first become active in early-late April. One study cited the first activity within four days after first bloom on Norway maple, and full bloom on border Forsythia.

The second generation is expected to start in late July or early August based on literature from Ohio, but our traps continue to capture adult beetles in early July.

Only females fly and emerge in spring to colonize new hosts. The adult female drills a hole approximately 1 millimeter in diameter, and hollows out a channel into the heartwood of small trees. The female tunnels into the sapwood of a small tree (2 to 50 centimeters diameter) and starts to culture a fungal food source, Ambrosiella hartigii. She lays her eggs (tiny, 1 millimeter, white, football-shaped) in the chamber. She lines the chambers with the Ambrosia fungus for the larvae, (also white, with three instars) to feed on before they pupate to develop as an adult.

It is this fungus that the larvae will feed on in the brood chambers, not the tree. It takes about 30 days for development from egg to adult. The ratio of females to males is about 10 to 1. The females can lay 2 to 54 eggs, depending on the host, but they average about 18.

Although the biology of this insect is not fully understood, we believe it has two generations per year in New York. Late in the summer, the beetles will migrate to a hole lower in the trunk to overwinter where researchers have found as many as 100 in a chamber. The beetles go into diapause in the summer and will not be active again until the next spring.

What Growers Need To Know
So far orchards where BSB has been detected are tall spindle or super spindle plantings in areas of wet soil conditions, or where no irrigation is available. Although these borers have a reputation of attacking stressed trees that are giving off ethanol volatiles, they also have been reported to attack apparently healthy trees. In the spring the trees look like they are weaker than uninfested trees and with some flakey bark. However, some look perfectly healthy. Other infested trees ooze sap or have fire blight oozing from the entry holes.

If the weather is calm and dry, growers might be lucky enough to see the “toothpick” frass pushed out of the holes. Upon close inspection, growers might find small pin pricks (1 millimeter in diameter), and the tiny black beetle in the hole. Using loppers or a pruning saw, growers can cut 1/8 to 1/4 inch from the hole to see the galleries that extend perpendicular to the trunk of the tree and are hollowed out a bit vertically to accommodate the brood of eggs; additional channels may be cut into the pith of the tree.

Although several chemical and biological controls have been tested, researchers have not yet identified anything that will stop these beetles. With a very wet spring or fall and poor soil drainage, you might see more damage the following season. The fungus the beetles carry with them can kill the trees as well and does not seem to be dependent on any particular weather condition.

What To Do If You Detect BSB
If growers identify black stem borer in their high density orchards, the recommendation (in ornamental nursery situations) is to rogue the infested trees (taking the rootstock as well), and take them to a location where they can be burned immediately. The grower might start a trapping program using ethanol-baited traps, checking them weekly.

A second trapping method we might be able to use for trap cropping is to adopt the system used by USDA — 12-inch beech loglets (1 inch in diameter) soaked in 15% ethanol for three days and deployed outside of the orchards as super-attractive targets — to time insecticides for when the beetles emerge from the galleries to find a new place.

As we looked in orchards where this problem was extensive last year, many trees showed crisp, blistered bark. We marked the trees and expected them to collapse the next spring. But to our surprise, many of the trees were still healthy — green trees with no sign of collapse.

It seems if we can find an effective control tactic to prevent continuous infestation of the trees in your high density plantings, tree removal may become unnecessary.

Control Methods
The ornamental nursery industry, where this is a serious pest, relies on pyrethroids on a two-week schedule which would certainly be a challenge in apples with concerns over how it would impact mite control. The nursery industry has also tested neonicotinoids, anthranilic diamides (cyazypyr, acelepryn), and tolfenpyrad and has not found them to be effective in controlling BSB.

We have nothing registered specifically for control of this pest except for Syngenta’s Warrior II or Winfield Solution’s Grizzly Z, lambda-cyhalothrin, labeled for tree borer species, but we have no experience or efficacy data to make any recommendations at this time. It is also expected that chlorpyrifos trunk sprays for borers may be effective, but will not prevent higher points of entry which have been seen as high as 4 feet in the tree.

We — along with Kerik Cox — are working on this pest to better understand the biology and identify viable controls. We are also trying to document economic damage for this pest so this issue can get more attention for research.

Topics: , , ,

Leave a Reply

Apples & Pears Stories
sweet cherry bloom
Apples & PearsCold Spell Hits Mid-Columbia Region
April 3, 2015
Cherry and grape growers use wind machines, irrigation to protect early blooms and buds from freezing temperatures. Read More
apple blossom in Pennsylvania
Apples & PearsAn In-Depth Look At Bloom
March 31, 2015
Do you know what happens after the bees fly away? Here's an in-depth look at what happens in spring. Read More
Apples & PearsPink Lady Apple Production Continues To Grow
March 30, 2015
Total production is up nearly 50% over 2009, and is expected to increase 33% in the next three years. Read More
Apples & PearsHow Will We Sell All These Apples? [Opinion]
March 30, 2015
Apple production is reaching heights that would have been unthinkable two or three decades ago. That's great news for growers — if we can sell them all profitably, Read More
Apples & PearsSounding Off On GMOs: The Arctic Apple Decision
March 27, 2015
Industry leaders share their feelings on the recently approved genetically modified apples. Read More
Apples & PearsMeet USApple’s Class of 2015 Young Apple Leaders
March 27, 2015
Young decision-makers see trip as an opportunity make sure the voice of the apple industry is heard by representatives. Read More
Pennsylvania hard cider guild logo
Apples & PearsPennsylvania Hard Cider Producers Founded Independent Trade Organization
March 25, 2015
The Pennsylvania Cider Guild is designed to help promote and educate members and consumers. Read More
The Latest
Gala green tip apple bloom
Apples & PearsApple Scab Spores Begin To Emerge In Pennsylvania
April 14, 2015
Now is a good time to apply copper sprays to protect trees. Read More
Apples & PearsWashington Apple Detective Finds ‘Lost’ Varieties
April 9, 2015
Works with university researchers to resurrect apples of the Palouse region. Read More
Bartlett Pears
Apples & PearsPears Examined For Probiotic Benefits
April 8, 2015
Study published in Food Research International highlights the nutritional benefits of a diet rich in pears. Read More
sweet cherry bloom
Apples & PearsCold Spell Hits Mid-Columbia Region
April 3, 2015
Cherry and grape growers use wind machines, irrigation to protect early blooms and buds from freezing temperatures. Read More
apple blossom in Pennsylvania
Apples & PearsAn In-Depth Look At Bloom
March 31, 2015
Do you know what happens after the bees fly away? Here's an in-depth look at what happens in spring. Read More
Apples & PearsPink Lady Apple Production Continues To Grow
March 30, 2015
Total production is up nearly 50% over 2009, and is expected to increase 33% in the next three years. Read More
Apples & PearsHow Will We Sell All These Apples? [Opinion]
March 30, 2015
Apple production is reaching heights that would have been unthinkable two or three decades ago. That's great news for growers — if we can sell them all profitably, Read More
Apples & PearsSounding Off On GMOs: The Arctic Apple Decision
March 27, 2015
Industry leaders share their feelings on the recently approved genetically modified apples. Read More
Apples & PearsMeet USApple’s Class of 2015 Young Apple Leaders
March 27, 2015
Young decision-makers see trip as an opportunity make sure the voice of the apple industry is heard by representatives. Read More
Pennsylvania hard cider guild logo
Apples & PearsPennsylvania Hard Cider Producers Founded Independent T…
March 25, 2015
The Pennsylvania Cider Guild is designed to help promote and educate members and consumers. Read More
Apples & PearsNeedles Found In Honeycrisp Sold At Grocery Store
March 24, 2015
Apples were believed to be tampered with; initial surveillance footage was inconclusive. Read More
Apples & PearsMonster Crops: How Much Is Too Much?
March 24, 2015
With larger-than-ever crops, more new varieties and uncertain markets, we explore the current state of apple production and what it means for the future of the industry. Read More
gmo apple
Apples & PearsFDA Concludes GMO Crops Innate Potato And Arctic Apple …
March 20, 2015
The agency says the evaluated varieties are as safe and nutritious as conventional counterparts. Read More
Apples & PearsIndia Eyed As Next Export Market For Washington Apple C…
March 17, 2015
Promotion plan includes focus on increasing shipments of Red Delicious in growing export market. Read More
Apples & PearsCompany Responsible For First GMO Apples Is Sold
February 27, 2015
Okanagan Specialty Fruits, the company behind the world's first non-browning apples, fetches $41 million. Read More
Apples & PearsNew Plant Growth Regulator Use Expanded
February 26, 2015
Ten more states grant registrations for Fine Americas’ new Kudos PGR. Read More
Apples & PearsFrom The Road: IFTA Conference Day 5
February 26, 2015
Carlson lecture highlights where IFTA has been and looks to the next generation to continue the legacy. Read More
Apples & PearsFrom The Road: IFTA Conference Day 4
February 25, 2015
Creating fruiting walls with mechanical hedgers can help increase light interception in the canopy, say researchers and growers. Read More