Lexington, Kentucky 40546
      
Nursery Update - A Kentucky Cooperative Extension Service Update for the Kentucky Nursery Industry
    
By Amy Fulcher, Extension Associate - Nursery Crops
University of Kentucky Department of Horticulture
Update #31
May 20, 2005

Insects
Ambrosia beetles

For the past 3 years reported nursery incidence of Ambrosia beetles have been minor in Kentucky (see Nursery Update #10, April 2, 2003). This year unprecedented Ambrosia beetle infestations were reported. There are many types of Ambrosia beetles but the Asian Ambrosia beetle (AAB) is considered to be one of the most serious. Due to the severe economic consequences of Asian Ambrosia beetle this year, a more indepth article than is normally in the Kentucky Nursery Update has been included this month.

The following includes excerpts from an article published in the TN Green Times written by Jason Oliver, Frank Hale, Nadeer Youssef, and Mark Halcomb, representing the TSU-IAGER, Otis L. Floyd Nursery Research Center and UT Extension.

AAB damage woody plants when the female beetle makes a tunnel in the trunk and introduces ambrosia fungus. External evidence of AAB attacks often consists of shot holes in the trunk or toothpick-like strands of sawdust and excrement. The adult AAB feeds herself and developing larvae on the ambrosia fungus growing in the tunnel. The combination of tunneling and the introduction of pathogens can result in rapid tree mortality. Five to 10 attacks can kill most trees with a caliper of 3 inches or less according to recent research from the University of Florida.

Ambrosia beetles usually over-winter as adult beetles. As a result, predicting adult emergence in the spring is difficult, because there is no temperature-dependent larval period prior to adult emergence. Instead, the adult beetles will remain inactive until temperatures become suitable for a flight, and then suddenly (and often unexpectedly) appear at the nursery site. Most ambrosia beetles, including the AAB, attack woody plants right before the break of plant dormancy. However, emergence times can vary greatly across regions and years, and therefore, the timing of bud break alone is not a reliable predictor of AAB activity.

Ornamental entomologists agree that trapping is the best way to monitor adult AAB activity. Traps have two main values: 1) they can be used to warn a grower when careful scouting of their crop should be underway (especially if a spray treatment is not being made), and 2) they can be used to direct the timing of spray treatments. Testimonials from Virginia state that when traps were used to time AAB sprays, 100% control was acheived. Most ambrosia beetles, including the AAB, are attracted to ethanol. Traps will be discussed and 2 Baker traps will be given out to participants at the "Putting Integrated Pest Management to Work in the Nursery" program next Wednesday (please see below).

Some growers have expressed concern that traps may attract AAB to their field site. Traps can be placed at a site away from the production area and still provide valuable information about AAB activity in the area. Another option is to remove the trap at the first appearance of AAB at the production site, but trap removal also eliminates information about AAB activity during the rest of the season. The general consensus among ornamental entomologists has been that traps do not increase the risk of crop attack. Likewise, we have not observed increased attacks on crops adjacent to our research traps, but instead traps provided considerable value in giving an early alert and indicating periods of intense AAB flight activity. One to three traps are usually sufficient for monitoring AAB activity in an area.

The first indication that you may have AAB in your trap will be a large number of small beetles suddenly appearing in the trap collection container. Sometimes several hundred beetles can appear in one day. Unfortunately, other species of ambrosia beetle will also respond in large numbers to traps used to monitor AAB, which can cause confusion. AAB are reddish-brown. The length of AAB is about twice the diameter of a 1/16-inch drill bit and about half the width of the same bit. The University of Kentucky is trying to determine the extent of AAB occurrance across the state. Please submit any samples that may contain AAB to your county Extension Office for identification.

If an ambrosia beetle infestation reaches the point that you are seeing toothpick-like strands extending from your tree, your management options are very limited. Burning the infested trees before the adults emerge is the safest option. Table 1 contains several guidelines that may assist you in reaching a decision about how to manage for AAB.

Labels we found for these active ingredients with language permitting commercial nursery use and specific rate recommendations for ambrosia beetles included: chlorpyrifos (Chlorpyrifos Pro 4, Dursban 50W, Prentox Dursban 4E) and permethrin (Perm-Up 3.2EC). The length of protection provided by a single treatment is currently unknown and multiple treatments may be required. Multiple generations of AAB occurring in Kentucky cannot be ruled out at this point.

Table 1. Decision Guide for Applying Spray Treatments Against Asian Ambrosia Beetle.

1) Have AAB been collected in traps?

Yes (Go to question 2)

No (Risk of attack is probably low)

2) Have trees broken dormancy?

No (Trees are at greater risk of attack. See Factors below to decide if a spray treatment may be needed)

Yes (Trees less susceptible to attack, but risk is still not zero. See Factors below to decide if a spray treatment may be needed)

     

Factor

Greater Risk

Lesser Risk

Plant Species

Cherry, chestnut, dogwood goldenraintree, hydrangea, lilac, maple, redbud, weeping mulberry, yellowwood, trees w/ past problem

Other Species

Crop Value

High

Low

Environmental Conditions

Drought, winter injury, late frost

Good

Site Conditions

Poor soil type, soil compacted, poor drainage

Good

Plant Condition

Trunk injury, herbicide damage, improper fertilization, over watered

Good

Plant Suitability to Site

Wrong cultivar or hardiness zone, plant requirements do not match site

Adapted

Past Problems at Site

Yes

No

Age From Transplanting

New transplant

Established

Other Pest / Disease Injury

Yes

No

Plant Source

Another region

Local

Proximity to Water

Close

Distant

Fertilizer Termination

After July

Before July

Plant Vigor

Low

Vigorous

Time of Year

March to May

June to February

Last Pyrethroid Spray

> 3-4 weeks

< 3-4 weeks

Image from the University of Missouri.

 
 

Putting Integrated Pest Management to Work in the Nursery
May 25, 2005
Location: Boone County Extension Office and Ammon Wholesale Nursery, Inc.
$20 per person

8:30-10:30 “IPM for the Nursery: What it is and How to Control Pests with IPM in Your Nursery” - Craig Adkins, NCSU Area Specialized Agent - Commercial Horticulture
10:30 - 10:45 Break
10:45 - 11:30 "Alien Invaders" – Joe Boggs, OSU Extension Educator and Horticulture Specialist
11:30 - 12:00 “Maple Miseries – The Latest on Combating Leafhoppers, Flatheaded Appletree Borer, Shoot Boring Caterpillars, and Maple Mites” - Bonny Miller, UK Entomology M.S. Student
12:00 - 1:00 Lunch travel to Ammon Wholesale Nursery
1:00 - 1:30"Using Technology to Out-Smart Pests: Pheromone Traps, Phenology, Tissue and Leachate Analysis, and Soil Sampling” – Amy Fulcher, UK Extension Associate for Nursery Crops
1:30 - 3:30 “Scouting Field and Container Nurseries for Insects and Diseases” - Craig Adkins, NCSU Area Specialized Agent - Commercial Horticulture
3:30 pm Pesticide CEU sign-up (5 general hours and 1 category specific for 3, 10, 12, and 19)

Scouting Report
Exit holes from the flatheaded appletree borer appeared during the last 2 weeks of scouting in central and south central KY. This is quite a bit earlier than average. Spray very soon if you are planning on spraying for this pest; it will soon be too late, if it isn't already. Lesser peachtree borers have been caught in pheromone traps the last two weeks, as well. Most traps are completely covered in this pest, in contrast to lilac borers, which averaged many fewer borers per trap (approximately 5 per week for the last week of April and first week of May). Consider spraying ornamental fruit trees for the lesser peachtree borer. For nursery applications there are a few product options: Onyx, Perm Up, Dursban TNP (sold by United Horticultural Supply) and Chlorpyrifos Pro 4 (sold by Micro Flow). Potato leafhoppers have been sighted on yellow sticky cards in Dr. Potter and Company's plot at the South Farm. Numbers are still low, however, research illustrated in Purdue's publication "Developing an Integrated Pest Management Program for Nurseries" E-213, explains that the action or spray threshold for potato leafhopper is an average of 3 leafhoppers per shoot, sampling 4 shoots per tree. Several trees should be sampled. If you wish to try to prune out shoot boring caterpillar from maples, cut open the swollen portion of the stem to determine if the larvae is still present or if it has pupated. If the larva is not present, pruning won't help control the pest but may help the appearance of the trees.

Source: Scouting report provided by Derrick Hammons, courtesy of KY IPM.

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