IN INTRODUCTION TO PLANT DISEASES, PART II-FUNGI & BACTERIA

Transcription

1 IN INTRODUCTION TO PLANT DISEASES, PART II-FUNGI & BACTERIA

2 FUNGI Fungi are composed of living filaments called hyphae Need an outside food source Pathogens of plants and animals, sometimes 300,000 species of fungi idescribed; d most are not plant pathogens

3 THE HUMONGOUS FUNGUS ARMILLARIA GALLICA In 1992, Armillaria gallica, a fungus found near Crystal Falls, MIcovered 37 acres, was estimated to weigh 10 tons and age was estimated at 1,500 yrs old. You may have seen this graphic on Uhaul trucks. Since then larger, older Armillaria spp. have been noted in CO and OR.

4 FUNGI THE GREAT DECOMPOSERS Fungi recycle nutrients by breaking down dead plant material. Fungi that live on dead plant material are called saprophytes.

5 MEET THE TROPH FAMILY Autotrophs Biotrophs Necrotrophs

6 AUTOTROPHS Synthesize their own nutritional titi needs (photosynthesis) Example: Green Plants

7 BIOTROPHS An organism that t can only live and reproduce on another living organism Example: powdery mildews, downy mildews, rust fungi Biotrophs are Biotrophs are also called obligate parasites.

8 NECROTROPHS A parasite that kills and obtains its nutrition from dead host cells Example: Sclerotium rolfsii, causes southern blight/southern stem rot. This fungus survives by producing spherical resting structures called sclerotia.

9 EXAMPLES OF FUNGAL DISEASES Mildews (Powdery and Downy) Rusts and smuts Vascular wilt diseases Root and stem rots Leaf spots and blights

10 POWDERY MILDEWS Powdery mildew can be managed with fungicides. Sprays can be initiated after signs of disease are visible, but don t wait too late. Powdery mildew on English oak. Easily identified by white mycelium Resistant species and cultivars are available for lilac, dogwood, crape myrtle, phlox, crabapple

11 DOWNY MILDEW ON IMPATIENS Downy mildew of impatiens has damaged landscape plantings in the U.S. in 2011 and 2012.

12 BOXWOOD BLIGHT OF BOXWOOD Defoliation of boxwood in one season due to boxwood dblight (Cylindrocladium buxicola). Boxwood blight was first discovered in the U.S. in NC and CT in Oct Photos courtesy of M. Inman, CT Ag Exp Station

13 RUSTS Cd Cedar apple rust is a heteroecious rust, requiring two unrelated hosts to complete its lifecycle. Autoecious rusts only require one host to complete Yellow leaf spots and rust colored pustules Numerous hosts including conifers, broadleaf plants their lifecycle. May also cause galls, twig dieback

14 APPLE SCAB Found on apple and crabapple Causes premature leaf drop Symptoms may be found on leaves and fruit Also found on pyracantha

15 Fungal leaf spot, twig blight and/or canker disease Favored by cool, wet weather Hosts: ash, dogwood, maple, oak, sycamore ANTHRACNOSE DISEASES

16 FUNGAL CANKER DISEASE Localized infection, often causing branch hdieback May follow drought stress Prune out dead branches to stop spread

17 1 YEAR LATER- CANKER HAS To prevent: irrigate to minimize i i water stress Prune out dead branches when they are observed or you could losethe whole plant MOVED TO MAIN STEM

18 ROOT ROT DISEASES Affected plants may be stunted, wilted Discolored, decayed roots Poor drainage, standing water, excessive irrigation, favor disease development Phytophthora hth root rot/juniper

19 BLACK ROOT ROT FOLIAR SYMPTOMS Black root rot is caused by the fungus Thielaviopsis. BRR causes a slow, progressive decline. Initial symptoms are yellow foliage; roots of infected plants are discolored and decayed.

20 ROOT SYMPTOMS OF BLACK ROOT ROT Dark, discolored roots on Japanese and blue holly, and inkberry are almost always a symptom of black root rot. Herbaceous hosts include: pansy, vinca, petunia

21 BACTERIA Single celled organisms much smaller than fungal spores Not visible to the naked eye Shaped like rods, spheres, helical

22 BACTERIAL DISEASES Soft rots Vascular wilts Leaf and fruit spots Crown gall Fire blight Citrus canker, Citrus Greening

23 BACTERIAL LEAF SPOT Xanthomonas leaf spot on English ivy.

24 BACTERIA STREAMING FROM PLANT TISSUE Bacteria streaming from a portion of a cabbage leaf infected with black rot. Photo courtesy P. Bachi, Univ of KY.

25 CROWN GALL Crown gall on a wisteria stem Tumors/galls on stems/roots Soft, spongy to wooden and corky with maturity Bacteria enter through wounds

26 FIRE BLIGHT A bacterial disease of apple, crabapple and pear. Symptoms at right include a classic symptom for fire blight, a shepherd s crook and a stem canker.

27 BACTERIAL LEAF SCORCH Leaf hoppers are the insect vectors of bacterial leaf scorch. The xylem inhabiting bacterium that is the causal agent plugs those vessels that transport water to leaves resulting in leaf scorch. Bacterial, vascular wilt disease of shade trees, especially pin oak