Ornamental and Tree Disease Update Jean Williams Woodward Extension Plant Pathologist University of Georgia Rose rosette 1
A. Windham 2
Shrub rose not Knock Out 3
Proliferation of shoots (rosette) 4
Rose Rosette Virus disease spread by eriophyid mite Causes proliferation of shoots Reddening of shoots Excessive thorniness Excessive thorns 5
Rose rosette management Rogue infected plants Prune affected shoots to the ground Removes symptoms and mites Doesn t remove virus completely Miticide applications Avid (or other abamectin generics) Floramite Magus Forbid Boxwood blight in CT (fall 2011) 6
Boxwood or Box Blight Caused by Cylindrocladium pseudonaviculatum (syn. C. buxicola) New to US in Fall 2011 Now in 13 states CT, DE, MA, MD, NC, NJ, NY, OH, OR, PA, RI, VA, AL Great concern for the green industry Infects all species and cultivars of boxwood Also infects Pachysandra (ground spurge) Has not been identified in GA (yet) Symptoms and Signs Leaf spots Dark stem lesions Foliage browning Rapid defoliation Tufting, white sporulation Leaf spots on Boxwood Leaf spots on Pachysandra 7
Nursery Concerns Spread easily via water splashed spores, tools, workers (spores are very sticky) Profuse sporulation Microsclerotia allow for survival 8
Spread on pruning shears Management Very difficult to control Discard infected plants immediately Bag and dispose Don t place in compost or cull piles Remove all fallen leaf litter and dispose Treat area with propane torch to burn litter Preventive fungicide treatments to protect plants from infection Chlorothalonil, fludioxonil, tebuconazole Fungicides after infection are ineffective 9
Look a like: Volutella Blight Look a like Volutella Blight (Volutella buxi) Often associated with weakened plants 10
Root disease still a problem Phytophthora and Pythium root and crown rot Requires wet soils/rooting medium Black root rot (Thielaviopsis basicola) Often overlooked More common than thought Herbaceous and woody plants 11
Phytophthora in landscapes Always associated with wet soils Over watering, excessive rain, poorly draining soils, soil compaction Poor root development on transplants Control Change site conditions Don t overwater Remove affected plants Subdue GR may help RootShield may help Phytophthora root and crown rot Symptoms Darkly discolored roots Root sloughing or snapping Foliage and stem dieback Wilting Death 12
Phytophthora in Liriope Fungicides 13
Selecting plants? Choose wisely. Black root rot Thielaviopsis basicola Cooler temperatures, wet soils, alkaline soil ph favor disease development Plants often infected during production Fungus survives in soil for years 14
Black root rot: Thielaviopsis basicola Yellowing foliage Leaf drop, dieback Photos by A. Windham 15
Black root rot on Helleri holly Two liners in one container Black root rot nibbling root tips 16
Darkly colored root tips Moves upward in root system; kills stems, then plant Off color foliage, yellowing and stem dieback 17
No roots from Thielaviopsis Pythium and Phytophthora likely Black root rot control Maintain soil ph at 5.8 or below Do not over water and plant in well draining mix Discard infected plants Sanitation! Fungicide drenches can help reduce infection Thiophanate methyl (3336, 6672) higher labeled rates Fludioxonil (Medallion) Triflumizole (Terraguard) Polyoxin D (Veranda) Use less susceptible plants 18
Oak leaf blister common in spring Cercospora leaf spot on redbud Tar spot on maple Powdery mildew on crapemyrtle Numerous leaf spotting diseases and powdery mildews affect landscape plants Resistant cultivars are often available London plane tree, crapemyrtle, dogwood, etc. Fungicides are rarely needed, except in nurseries Daconil, Banner MAXX, Heritage are excellent on most leaf spot diseases 19
Landscape Sanitation Remove leaves Pathogens survive on fallen leaf litter and last year s leaves Remove these prior to bud break to reduce infection of new leaves Tree failure 20
Fungal stroma at root flare 21
Fungal Identification Does it have a stipe? Is the cap hard or soft, smooth or rough? Does it have pores, tubes, gills, or teeth on the underside of the cap/conk? What color is its flesh? What color are the spores? Does it change color when bruised? Any other features? What is the host? Wood decay fungi Brown rots Breakdowns cellulose first and leaves lignin Loss of strength early, wood crumbles, shrinks Cubical rot, dry rot White rots Rapid breakdown of lignin and eventually cellulose Wood is spongy, stringy Early infection stages show little strength loss 22
Inonotus dryadeus (White butt rot or Weeping conk ) Often massive, annual basidiocarps in fall Causes a white spongy rot 23
New basidiocarps grow over and around past year s basidiocarps Inonotus species weep when fresh 24
Ganoderma applanatum Questions? 25