All posts by ddlang

Blueberry Maggot

Blueberry maggot was first detected in Wisconsin in the summer of 2016 in Adams and Sauk Counties.  This pest feeds inside blueberry fruit and caused damage in commercial blueberry production in the eastern and southern United States, as well as in eastern Canada.  This insect is expected to eventually have a significant impact on blueberry production in Wisconsin.

Blueberry maggot adult with characteristic wing patterns (left) and larva (right). (Photos courtesy of Rufus Isaacs, Michigan State University)
Blueberry maggot adult with characteristic wing patterns (left) and larva (right). (Photos courtesy of Rufus Isaacs, Michigan State University)

Appearance:  The adult blueberry maggot is a fly that is approximately 3/16 inch long and resembles a small housefly, but with dark bands on its wings.  Larvae (or maggots) are legless and can grow up to 5/16 inch in length.  Each larva has a single hook-like tooth at its mouth end.  Blueberry maggots are very similar in appearance to the closely related apple maggot, with adults of both being virtually identical in size and appearance (including wing patterns).  However, apple maggot does not feed on blueberries.

Host Range:  Blueberry (Vaccinium corymbosum) is the only commercially-grown fruit crop affected by blueberry maggot.  Wild hosts include plant species in the genera Vaccinium and Gaylussacia including wild blueberries, lingonberry, dangleberry, deerberry and huckleberry.

Symptoms and Effects:  A single larva feeds inside each fruit causing the berry to become soft as it develops.  Damage may go unnoticed until after harvest, when maggots crawl out of fruit and become visible among fresh fruit or in processed blueberry products (e.g., jams, preserves, pie fillings).

Life Cycle:  Adult blueberry maggots begin to fly in June or July, and continue to fly through August.  Females feed and mate for at least one week before they move to blueberry plants to begin laying eggs.  Females lay a single egg under the skin of a nearly ripe blueberry fruit and can lay up to 100 eggs during their approximately one month-long life span.  Eggs hatch within one week and damage from larvae generally first appears in mid-July, continuing until blueberries have been harvested.  Each maggot feeds in a single blueberry during its two- to three-week development.  After completing their development, larvae drop to the ground and overwinter as pupae in the upper few inches of soil.  A distinctive characteristic of the blueberry maggot is that, although most pupae develop to form adults by the following spring (completing one generation of the insect in a year), some pupae remain underground and do not mature for two or three years.

Monitoring:  Monitor for blueberry maggot adults several weeks before blueberries begin to ripen (usually in early June) using yellow sticky cards impregnated with a feeding attractant (ammonium acetate or ammonium carbonate).  You can buy cards that are pretreated with the attractant, or buy the cards and attractant separately and apply the attractant yourself.  Fold the sticky cards in a V-shape with the yellow side facing down and put up two traps for every five acres.  Because blueberry maggot is currently not widespread in Wisconsin, you can check cards weekly until you find the first adult.  After this initial find, check cards every few days.  Once you find an average of greater than one adult per trap for several days in a row, begin chemical treatments (see below).  Note that the feeding attractant is not specific for blueberry maggot, so you may find other types of flies on the cards – use a hand-lens or magnifying glass to positively identify any blueberry maggot adults.  Remember that blueberry maggot and apple maggot look very similar, but that apple maggot does not feed on blueberries, so flies trapped in blueberry fields/patches are most likely to be blueberry maggot.

Once you have detected adults, you can also test fruit for the presence of larvae.  Collect 100 berries from throughout your planting.  Then break the skins of the berries and mix the berries with a salt-water solution (1 part salt to 4 parts water).  Larvae will float to the surface.  The number of larvae you find represents the percentage of fruit infested.

Control:  Cultural control methods can be useful in preventing blueberry maggot infestations.  Remove weeds to eliminate habitat for blueberry maggot.  Remove wild blueberry and huckleberry plants as these can serve as alternate hosts for the insect.  Harvest fruits thoroughly and heat (to at least 120°F) or freeze any damaged or unusable fruits to kill blueberry maggot larvae.  This is particularly important if you compost fruit, because blueberry maggot pupae can readily survive in compost and serve as a source of an infestation in future years.  Clean soil thoroughly from equipment or beehives that might be moved between blueberry patches.  Blueberry maggot pupae can easily be moved in soil.

A blueberry maggot trap. (Photos courtesy of Rufus Isaacs, Michigan State University)
A blueberry maggot trap. (Photos courtesy of Rufus Isaacs, Michigan State University)

As noted above, start chemical control once you find an average of greater than one adult blueberry maggot per trap for several days in a row.  Alternatively, if you have had a serious problem in the past, you may want to start sprays one week after you trap your first blueberry maggot fly.  Continue sprays every seven to 10 days through harvest.  Some reduced risk active ingredients, such as novaluron, spinetoram, and spinosad are most effective when used as soon as flies are found in traps.  In addition, consider choosing a product that also provides control of spotted wing drosophila, another serious blueberry pest (see University of Wisconsin Garden Facts XHT1237 for details).  Spinosyn, spinetoram, diamide, carbamate, pyrethroid, and organophosphate-containing insecticides are effective against both insects.  Be sure to rotate use of at least two active ingredients with different modes of action to help delay development of insecticide resistance (see http://www.irac-online.org/modes-of-action/ for details), and be sure consider the effects of sprays on non-target (e.g., beneficial insects).  Finally, because you will be spraying ripe berries, pay particular attention to the pre-harvest interval when choosing insecticides.  Check the most recent Midwest Fruit Pest Management Guide (see https://learningstore.uwex.edu/Midwest-Fruit-Pest-Management-Guide-2017-P1785.aspx) for complete product recommendations.

For more information on or help diagnosing blueberry maggot:  Contact your county Extension agent.

February: The Facts Ma’am, Just the (UW Garden) Facts

The winter months are the prime period at the PDDC when staff are able to concentrate on outreach activities that do not involve diagnosing diseases on plant specimens.  One of the major outreach efforts of the PDDC has been and continues to be the University of Wisconsin (UW) Garden Facts fact sheet series.

The UW Garden Facts were originally conceived and developed by the University of Wisconsin-Extension Horticulture Team.  These one-page fact sheets were designed to be user friendly for home gardeners.  They are short, concise and easy to read, with an emphasis on answers to questions that homeowners often ask about horticultural issues.  Due to their popularity, the UW Garden Facts series was eventually expanded to include UW Farm Facts (covering more agriculture-oriented topics) and UW Pest Alerts (covering new and emerging disease/pest issues in both the agricultural and horticultural arenas).

The UW Garden Facts/Farm Facts/Pest Alerts series currently has over 250 titles, all of which are available in several formats for download free-of-charge from the “Fact Sheets” section of the UW-Madison/Extension Plant Disease Diagnostics Clinic website.  A web friendly version of the fact sheets (for reading online) is also available on the website.  If you are a horticulture or agriculture professional and would like to distribute the fact sheets as part of your business (which is encouraged), there is space to customize each fact sheet with personal or business information (e.g., a company logo).

A two CD compilation of University of Wisconsin Facts is also available.  The compilation contains the full set of the fact sheets and costs $30 for the general public and $20 for Master Gardener volunteers, plus shipping and handling (approximately $3.00 per CD).  To order a compilation, contact:

Brian Hudelson
Plant Disease Diagnostics Clinic
Department of Plant Pathology
University of Wisconsin-Madison
1630 Linden Drive
Madison, WI  53706-1598
Telephone:  (608) 262-2863
Email:  pddc@wisc.edu

Complimentary copies of UW Garden Facts/Farm Facts/Pest Alerts are also available in the display outside the PDDC (Rm. 183 Russell Labs at the address listed above), and complementary horticulture-related disease titles will also be available February 9-11, 2018 at the PDDC booth (booth 833-834) at Garden Expo 2018.  To keep up to date on new and revised fact sheets, be sure to follow the UW-PDDC on Facebook and Twitter @UWPDDC, or contact the PDDC at the phone number or email address listed above.

Happy reading!!

San José Scale

San José scale (Diaspidiotus perniciosus) is a fruit tree pest that can be found in most fruit growing regions of the United States.  Native to China, this insect was introduced into the United States in the late 1800s.  In well-managed orchards, populations of San José scale are generally too low to cause economic damage.  In poorly managed orchards however, populations can become high enough in one to two growing seasons to cause tree and fruit injury.  Once established, San José scale can be difficult and expensive to control.  San José scale is of historical interest because, in the early 1900’s, it was the first insect observed to develop resistance to an insecticide.

San José scale damage on apple fruit (left). San José scale black cap stage (center), female (upper right) and male (lower right). [Photos courtesy of Greg Krawczyk (Penn State University), E. Beers (Washington State University) and S. Schoof (North Carolina State University).]
San José scale damage on apple fruit (left). San José scale black cap stage (center), female (upper right) and male (lower right). [Photos courtesy of Greg Krawczyk (Penn State University), E. Beers (Washington State University) and S. Schoof (North Carolina State University).]
Appearance:  San José scale females are yellow, wingless and legless, have a soft, globular shape and are approximately 1/12 inch long.  Male scales are 1/25 inch long, are yellowish-tan with a dark band across the back and have wings and long antennae.  Immature San José scales (called nymphs) go through three stages (crawler, white cap, and black cap).  Crawlers are roughly the diameter of the tip of a pin, are yellow, and have six legs and antennae.  Crawlers develop into the white cap stage as they become immobile and secrete hard, white, waxy coverings.  The black cap stage follows as the waxy coverings turn gray-black.

Host Range:  San José scale feeds on a variety of fruit hosts including apple, pear, plum, cherry, peach, apricot and berries (e.g., raspberry, blackberry), as well as on nut-bearing trees (e.g., walnut) and many ornamental trees and shrubs (e.g., elm, maple, mountain-ash, serviceberry, juniper, white cedar, yew).

Symptoms and Effects:  San José scale sucks sap from branches, leaves and fruit causing overall decline in plant vigor, growth, and yield.  If left uncontrolled, San José scale can ultimately kill plants.  On fruits, San José scale feeding causes slight depressions with red to purple haloes.  If San José scale populations are low, fruit damage is usually concentrated on the bottom of the fruit.  When infestations occur early in the season, fruit may become small, deformed, and poorly colored.  Damage by San José scale (even cosmetic spotting) decreases fruit quality and in commercial settings makes the fruit more difficult to sell.

Life Cycle:  San José scale can complete its life cycle in approximately 37 days.  There are typically two generations of the insect each year, and generations overlap so that all stages of the insect occur at the same time during the summer.  San José scale overwinters in the black cap stage.  Development of the insect resumes in spring when temperatures exceed 51°F.  Around petal fall, mature females and short-lived males emerge.  Males can fly from tree to tree, but females move very little.  After mating, females produce approximately 400 live crawlers over a period of six-weeks.  The first generation of crawlers appears between early and mid-June, with white and black cap stages developing over approximately the next month.  A second generation of adults appears between July and early September.  If warmer temperatures continue into the fall, a third generation of San José scale can occur between late October and early November.

Monitoring:  The first indication of a San José scale problem may be when infested fruit is found at harvest or (in commercial settings) at packing.  However, sometimes the insect can be found earlier on branches.  If a San José scale infestation is detected, careful examination of trees/orchards during dormancy can help determine the level of infestation and the extent of spread.  Watch for trees that retain leaves during winter (a good indication of a San José scale infestation) and check both branches and trunks for the insect.  Mark (e.g., with flagging tape) infested areas on trees to identify where sprays should be applied the following growing season.

In the spring and summer, use pheromone traps to detect the presence of males.  Begin using traps at the pink stage of apple flower bud development, in areas where infestations have been detected.  Place traps on the northern or eastern side of trees at a height of six to seven feet.  Check traps at least weekly.  Traps are effective for four to six weeks.

Monitor for crawlers by wrapping two-sided sticky electrical tape (coated with a thin layer of petroleum jelly) around infested tree limbs at both ends of the infested area.  Start checking tape for crawlers approximately four to six weeks after bloom.

A San José scale pheromone trap.
A San José scale pheromone trap. (Photo courtesy of S. Schoof, North Carolina State Univeristy)

Control:  The best strategy for managing San José scale is to prevent serious infestations.  The best cultural control is to prune out infested branches.  This reduces scale numbers and opens up the tree canopy so that if spray treatments are used, there is better penetration.  Several parasites and predators attack San José scale; however, use of these alone does not provide enough control to prevent damage.

The most effective spray control for San José scale is the use of 2% horticultural oil with or without an insecticide just before or right after bud break, but before flowers open.  During this period San José scale resumes its development after being dormant during the winter and the sprays will smother the insects.  After applying horticultural oil, continue to monitor for adults and crawlers (as described above) and if you still find active San José scale, consider using chemical insecticides for additional control.  Insecticides containing insect growth regulators (e.g., pyriproxyfen or buprofezin), neonicotinoids, organophosphates, or spirotetramat can be effective.  Start applications when you find the first adults in pheromone traps or the first crawlers on sticky tapes (usually around early to mid-June).  Apply another spray approximately 10 days later if you continue to find active crawlers.  When using two applications, be sure to use two products with active ingredients in different Insecticide Resistance Action Committee (IRAC) chemical classes (i.e., with different modes of action) to delay development of insecticide resistance.  See http://www.irac-online.org/modes-of-action/ for guidance.  Note that late-fall and postharvest applications are NOT effective for San José scale control.  Also, remember that whenever you use insecticides, you should consider the effects of products on non-target and beneficial insects.  Check the current year “Midwest Fruit Pest Management Guide” (available at https://learningstore.uwex.edu/) for additional insecticide recommendations.

For more information on San José scale:  Contact your county Extension agent.

January: 2017 in Review

The PDDC was a busy place in 2017.

Clinic staff processed 1445 samples, with samples coming from every county in Wisconsin other than Lincoln, Menominee and Price Counties.  The PDDC also received samples from FL, IA, IL, ME, MI, MN, MO, NY, PA, SD, TX and WA.  I personally also provided digital disease diagnostics via email and through the UW-Extension PlantDOC online diagnostic website.  I also continued with my interaction with members of the Association of Specialty Cut Flower Growers via their Facebook page, providing plant disease expertise for the group.  And of course, the phone rang off the hook for much of the year as I talked with folks about their plant disease problems.

In addition to my clinic duties, I also spent a fair amount of time providing plant disease outreach around the state.  In 2017, I did 91 talks/presentations/workshops visiting 19 Wisconsin counties in the process.  My biggest outreach event (in terms of time and effort) was, as always, Wisconsin Public Television’s Garden Expo.  During my three days at the event, I gave two talks on diseases of herbaceous ornamentals and helped answer questions with Lisa Johnson of Dane County UW-Extension to a standing-room-only crowd of almost 300 at Larry Meiller’s Garden Talk session.  I also had a steady stream of visitors to the PDDC booth all three days and pretty much talked with and answered questions for folks the entire time.  I distributed 3,024 University of Wisconsin Garden Facts fact sheets, 850 brochures/informational handouts of various kinds and 99 handouts for my talks.  Across all of my talks/presentations/workshops in 2017, I interacted with just over 300,000 people.  A big thanks goes out to Larry Meiller for having me on his radio show which has a HUGE listenership.

On a personal note, I had wonderful opportunity to visit New Zealand and eastern Australia for three weeks in late November and early December (their late spring).  I had to smile as I walked off the plane in Auckland, NZ to be greeted by a warning poster about brown marmorated stink bug, which has yet to arrive in the country.  On my first full day in NZ, I took a beautiful ferry ride from Auckland to Waiheke Island to hike, only to find a warning sign about the recently described Phytophthora agathidicida which is causing dieback in native kauri trees.  There was even a station at the entry point of the hiking area with disinfectant to use on my shoes!  And as I traveled around the country, I noted some very stunning invasive plants.  Common or Scotch broom was blooming everywhere in the mountains around Queenstown, and lupines covered acres and acres of the valleys as I drove from Queenstown to Christchurch.  Both were in full, spectacular bloom.  And on a helicopter trip to Milford Sound, I noticed huge areas on the mountainsides where all of the trees were brown and dead.  These turned out to be nonnative pines that were being killed in an attempt to reestablish native flora.  What a trip!!

Invasive Lupine
Acres of of invasive lupines line New Zealand roadways.
Invasive Broom
Scottish Broom adds a vibrant, if invasive, touch of color to New Zealand mountains.

Many thanks to Susan Lueloff (the PDDC Assistant Diagnostician and molecular diagnostician extraordinaire), John Lake (my hard working student hourly and lab cleaner supreme), Ann Joy (she of the nimble data entry fingers) and Dixie Lang (webmistress and database guru) for helping me keep my sanity and making 2017 such a fun year.  Now onward to 2018!  Let’s see what the new year has to offer.

For addition information on the PDDC and its activities, check out the PDDC website, follow the clinic on Twitter or Facebook (@UWPDDC) or contact the clinic at pddc@plantpath.wisc.edu.

December 2018

Interested in scheduling Brian Hudelson for presentation, workshop or other outreach activity?
Check out the calendar below to find out if Brian might have the date open.
Contact Brian directly [bdh@plantpath.wisc.edu or (608) 262-2863] to verify his availability.

 

November 2018

Interested in scheduling Brian Hudelson for presentation, workshop or other outreach activity?
Check out the calendar below to find out if Brian might have the date open.
Contact Brian directly [bdh@plantpath.wisc.edu or (608) 262-2863] to verify his availability.

November 10, 2018

Growing Healthy Plants – Basics in Plant Disease Management
(10:00 AM – 11:30 AM, Janesville, WI)

 

October 2018

Interested in scheduling Brian Hudelson for presentation, workshop or other outreach activity?
Check out the calendar below to find out if Brian might have the date open.
Contact Brian directly [bdh@plantpath.wisc.edu or (608) 262-2863] to verify his availability.

September 2018

Interested in scheduling Brian Hudelson for presentation, workshop or other outreach activity?
Check out the calendar below to find out if Brian might have the date open.
Contact Brian directly [bdh@plantpath.wisc.edu or (608) 262-2863] to verify his availability.

September 7, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)

September 14, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)

September 21, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)

September 22, 2018

Plant Diseases in History
(11: 00 AM – 11:45 AM, Eau Claire, WI)

Growing Healthy Plants – Basics in Plant Disease Management
(2:45 PM – 3:30 PM, Eau Claire, WI)

August 2018

Interested in scheduling Brian Hudelson for presentation, workshop or other outreach activity?
Check out the calendar below to find out if Brian might have the date open.
Contact Brian directly [bdh@plantpath.wisc.edu or (608) 262-2863] to verify his availability.

August 2, 2018

Diseases of Petunias
(TBD, Madison, WI)

August 3, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)

August 10, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)

August 17, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)

August 18, 2018

West Madison Agricultural Research Station Horticulture Open House
(9:00 AM – 1:00 PM, Madison, WI)

August 24, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)

August 31, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)

July 2018

Interested in scheduling Brian Hudelson for presentation, workshop or other outreach activity?
Check out the calendar below to find out if Brian might have the date open.
Contact Brian directly [bdh@plantpath.wisc.edu or (608) 262-2863] to verify his availability.

July 6, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)

July 13, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)

July 20, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)

July 27, 2018

Wisconsin Horticulture Update – PDDC Report
(9:40 AM – 9:50 AM, Madison, WI)