Fungicide Injections Affect Dutch Elm Disease and Internal Decay

Summary: Fungicide injections affect Dutch elm disease and internal decay in American elms, according to the February 2020 Arboriculture & Urban Forestry.

An American elm (Ulmus americana) destroyed by Dutch elm disease: Joseph OBrien, USDA Forest Service, Bugwood.org, CC BY 3.0 United States, via Forestry Images

Fungicide injections of American elms affect Dutch elm disease and internal density, according to an article by Nicholas J. Brazee and Robert E. Marra in the January 2020 Arboriculture & Urban Forestry.

The article Incidence of Internal Decay in American Elms (Ulmus americana) Under Regular Fungicide Injection to Manage Dutch Elm Disease broaches beating Ophiostoma novo-ulmi fungal pathogens. Nicholas J. Brazee at the University of Massachusetts in Amherst and Robert E. Marra at Connecticut Agricultural Experiment Station in New Haven consider drilling-wounded root flares. Bleeding cankers, cracked bark, discolored sapwood and, maximally, one-fifth of sugar-transmitting, water-transporting trunk tissue disrupted or dead denote chemical injuries from drilling-hole, fungicide-injected, lower-bole, root-flare wounds.

Thiabendazole hypophosphate fungicides encourage basdiomycete, wood-decaying fungi; ensure ebbing natural-defense, tylosis-formation, wound-closure responses, in xylem vessels above injection sites; and exorcize wounded wood-colonizing by hyphomycete fungi.

Twenty-first-century techniques feature high-quality drill bits for fewer surrounding-tissue wounds and small-diameter, well-spaced injection sites whose internal decay electrical-resistance and sonic-wave tomography accurately, minimally invasively fathoms.

Gauging fungicide-injected long-term effects as primary goal generated additional objectives of gathering suburban and urban internal decay incidence and severity data and supporting elm disease-controlled management. PiCUS software herded sequential sonic hammer-tapped sound waves and inter-measuring-point distances into colorimetric-scaled images of brown, intact-wooded, higher and green, magenta, blue decaying-wooded lower relative velocities. Electrical-resistance tomography (ERT) interprets deviations from wood homogeneity into maps of high-resistivity, low-conductivity, maximum-density, moistureless, nondecayed, red-, orange-, yellow-imaged sound wood, brown-imaged in sonic-wave tomography (SoT).

Blue-imaged ERT judges maximum-density, moist wood, brown-imaged in SoT, as lower trunk-colonizing bacterial wetwood or as incipient internal decay from fungicide injections against Dutch elm disease.

Blue-imaged versus non-blue ERT and green-, magenta-, blue-imaged versus non-brown SoT respectively know moist, reduced-density and low-resistivity, high-conductivity, moisture-free, reduced-density wood as active decay and cavities.

Twenty-eight of 91 fungicide-injected, 35 of 119 noninjected and 63 of 210 sampled elms logged statistical similarities, not significant differences, in 31-, 29-, 30-percent decay-nondecay proportions. Breast-height and sample-height classes II, III and IV respectively manifested 75- to 100-, 100- to 125-, 125-plus-centimeter versus 100- to 125-, 125- to 150-, 150-plus-centimeter diameters. They netted inter-class, significant, statistical differences in mean percent decay between their breast-height and sample-height diameter class II and their breast-height and sample-height diameter class IV.

Most-membered decay class I, 75-plus-percent undecayed, and least-membered IV, 75-plus-percent decayed, observed 13 and 83 mean percent internal decay from fungicide injections against Dutch elm disease.

Decay classes II and III presented decay ranges of 25 to 50 and 50 to 75 percent and mean percent decay of 33 and 63 percent.

High decay incidence and severity predictably queue with fungicide-injected, large-diameter American elms even as breast-height and sample-height diameters never qualify as reliable incidence and severity predictors. Sampled trees revealed 30- and 39-percent decay incidences and mean severity in Connecticut; Massachusetts; Minnesota; New Hampshire; New York; Rhode Island; Washington, D.C.; and Quebec, Canada. Almost 50 percent of the decay-resistant, fast-growing, long-lived, sampled American elms showed maximum-density, moist heartwood suggestive of incipient decay or of decay-resistant, heartwood-sheltered, sapwood-sheltering wetwood bacteria.

Perhaps wetwood bacteria toughen American elms against internal decay from fungicide injections against Dutch elm disease by triggering low-oxygen anaerobic, no-oxygen hypoxic, wood-decaying fungi-unfriendly wood tissue.

injections of Dutch elm disease (DED) fungicide into root flares of American elm (Ulmus americana): Roland J. Stipes, Virginia Polytechnic Institute and State University, Bugwood.org, CC BY 3.0 United States, via Forestry Images

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

An American elm (Ulmus americana) destroyed by Dutch elm disease: Joseph OBrien, USDA Forest Service, Bugwood.org, CC BY 3.0 United States, via Forestry Images @ https://www.forestryimages.org/browse/detail.cfm?imgnum=5037070

injections of Dutch elm disease (DED) fungicide into root flares of American elm (Ulmus americana): Roland J. Stipes, Virginia Polytechnic Institute and State University, Bugwood.org, CC BY 3.0 United States, via Forestry Images @ https://www.forestryimages.org/browse/detail.cfm?imgnum=5334063

For further information:

Brazee, Nicholas J.; and Robert E. Marra. January 2020. "Incidence of Internal Decay in American Elms (Ulmus americana) Under Regular Fungicide Injection to Manage Dutch Elm Disease." Arboriculture & Urban Forestry 46(1): 1-11.

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