Underlying Superficial Causes Plant Problem Diagnostics: dead foliage Methods Tools Techniques Coniothyrium leaf spot ugly plant moisture Jenny Rebecca Glass leaf spot WSU Puyallup Plant & Insect Diagnostic Laboratory fungal prune out inoculum 1 4 Wouldn’t it be nice if every plant problem How can you was easy to diagnose… sharpen your diagnostic skills? 10 x 5.5” image PRACTICE PRACTICE PRACTICE Grape erineum mite (eriophyid mite damage) 5.5 x 7.5” image 2 5 No microscope. No plant pathology Key to mastering plant diagnostics is studies. What is a Master Gardener Framing Your Mindset Diagnostician supposed to do? You can choose your attitude Rely on what you DO HAVE!! Experience with plants and problems in other arenas • Impossible vs. Challenging • Pointless vs. Progressing Use common sense diagnostics • Tedious vs. Methodical (who, what, where, when, why, how?) Ask those questions!! Consider numerous hypotheses and see what the evidence suggests relative to the ideas Have fun & learn! Make effective use of tools and resources snowberry insect galls 3 6 1
Collaborate with others to help figure out Come prepared for achieving an the cause of plant problems accurate diagnosis Plant Problems Should Be Avoided 10 x 5.5” image Client is an ally, not enemy You’ll Need: if Possible: • You are a team • Involve client in process Appropriate Diagnostic Materials • Find common ground (hand lens, cutting/digging tools) Willingness to Investigate Share your knowledge Suitable Sample Material & use your skills Complete Background Info 7 10 Develop and Use a Strategic Plan to Investigate Unknowns Mnemonics & other Memory Aids Prolegs 1: Gather information on the plant(s) affected & the Can be Helpful Count care & conditions surrounding the developing 1 2 3 4 5 6 Friendly firs/ Spikey spruces S A W F L Y problem Xylem up- Phloem down Or make up your own… 2: Check for clues (symptoms and signs) and their DS distribution patterns, as well as what is normal, to develop logical ideas as to the likely problem cause 3: Work to find convincing evidence to prove what is the origin of the problem 5.5 x 7.5” image 4: Employ management strategies & evaluate photo source: results http://www.natureblog.org/whats-the-difference 8 11 If there isn’t enough material or Diagnosis of Plant Problems: information to work with, educate the client Stepwise analysis of possible origins on what would be helpful. Don’t guess! plant 10 x 5.5” image attributes abiotic biotic pathogenic: physical insect/mite: 1. Fungal/ chemical F N 1. feeding habit e Oomycete mechanical M P 2. lifecycle 2. bacterial g fungi water 3. viral 4. nematode Hint: After, assessing “macro” organisms information & sample, use the “fortune teller” test 9 12 2
C.L.U.E.S. Symptoms come with a dazzling array of Courtesy: Heidi Kratsch, Univ of Nevada: terminology & associations…. C. Collect Information 10 x 5.5” image Necrosis Wet areas Blight Inner leaves L. Look for Patterns Dieback South side U. Use References Leaf spot Near ground Chlorosis By fan E. Eliminate Common Defoliation After frost Causes Stunting Terminal S. State your Tentative Gall growth Holly hedge infected with the Oomycete Distortion Vein-limited Diagnosis flowering Prunus excessive soil moisture Phytophthora pathogen holly leaf & shoot blight Rot In a row Or Try SOLUTION FINDING Decay Look for what IS WORKING 13 16 Effective Patterns related to distribution of symptoms & signs Investigative can shed light on likely origins of damage Techniques 1. Let the facts reveal themselves SymPtom: Abiotic Biotic Biotic Plant Damage (Nonliving) (Diseases) (Insect & Mite Pests) 2. Ask open-ended Signs None May be visible May be visible questions Distribution of Uniform Random Random symptoms Strongly one-sided Onset of Symptoms Rapid Gradual Gradual 3. Work to recognize Sign: unrelated Organism Progression Start & stop Spread with time Spread with time Causing the information/ Typically Damage Typically narrower Species affected Nearby & unrelated narrower host host range observations range 5.5 x 7.5” image 14 17 Sometimes a uniform appearance also Check plant for symptoms & signs. indicates a very high population of the pest Note healthy attributes too. or pathogen sign: physical presence of pathogen or pest 10 x 5.5” image Severe lacebug feeding injury to azalea (above) Symptom: Epidemic level of Lophodermium needlecast (left) response of plant Dogwood powdery mildew to problem 15 18 3
Be on the look Abiotic/Nonliving Stresses: out for What is happening around the plant? (soil, weather, cultural practices, neighboring influences) exceptions 10 x 5.5” image Cold Nutrients Injury/Wounds Wind Heat Pesticides 19 22 Many observed problems are associated with abiotic (nonliving) stresses rather than pest or pathogen injury Noctua pronuba Blossom 10 x 5.5” image Yellow underwing end rot’s moth larvae have calcium deficiency been problematic on issue is lawns recently but often can also feed on associated with other hosts, such as uneven vegetables watering conditions 20 23 Common local stresses Plants can come in contact with growth- Develop a basic regulating chemicals in many ways Chewing damage (insects and animal) understanding Piercing/sucking pests of general Fungal pathogens: Tomato 10 x 5.5” image pathogen leaf spot damage from blights herbicide powdery mildews groups and aminopyralid (slow rusts to breakdown) in vascular wilts stresses or compost, manure, or soil Fungal-like water-molds (Oomycetes) familiarity with Phytophthoras Pythiums Can be confused with references Downy Mildew other growth regulation issues such Bacteria- as virus infection or Pseudomonas toxic insect saliva soft rot injury 5.5 x 7.5” image Virus 21 24 4
Arthropod injury (Insects and Mites) Plant diseases 3 main types of damage: holes/tunnels (chewing), may develop stippling (piercing/sucking), & growth abnormalities when a host Management: Avoid high pest populations when and pathogen practical through diversity of plant interaction type (resistance) and predators. occurs under Sanitation: squish pests on an environment observation or prune out/wash off conducive for Mastery of Plant Pathology Tolerance Diagnostics involves close that disease. consideration of problem Insecticides (pesticide): if present attributes beyond simply the appearance of the damage & damage from population reaches a threshold of concern 5.5 x 7.5” image Photo: bean spider mites: du Toit; beet leafminer: Freeman 25 28 Plant Pathogens But remember, not all arthropods found in (Fungi & Allies, Bacteria, gardens/landscape are pests... Viruses & Nematodes) Management: Pest: brown marmorated stink bug (BMSB) Work to avoid!! Use Disease-resistant material. Rotate crops. smooth shoulder white spots Sanitation: remove infected plant material Identify pathogen group to help key into other management options Environmental Manipulation: keep foliage dry, avoid overwatering soil Native: Brochymena Fungicides (pesticide): Most function preventatively beneficial predator 26 29 Numerous animals can also feed on plants. Close examination & often microscopy Check for teeth marks and fecal material. are required to see fungal signs Baiting or the use of cameras can pinpoint animal. Paired teeth marks suggest rodent cause 27 30 5
Fungal leaf spot pathogens can Stereo Microscopy: thrive in the during moist periods 10 x 5.5” image Typically 5x to 40x the unaided eye Uses: examine larger objects, such as arthropods, look for fungal sporulation structures, helps target where to select material from for compound microscopy How: typically no special preparation. Just place material under scope and adjust focus first, then magnification Puget Sound/ PNW weather conditions often promote fungal Septoria rubi on Rubus pathogen development 31 34 Venturia : Apple scab can infect blossoms, Compound Microscopy: leaves, twigs and fruit Usually several settings: 40x, 100x, 200x, 400x the unaided eye Uses: the small stuff How: Sticky tape method: lay tape across the area of interest, placed onto drop of water, and then examine at lowest magnification first Cut tissue method: needs to be SMALL. Cut piece of tissue of interest and then slice, dice, smash (as needed) to get material thin enough to investigate, place on water, cover with coverslip 32 35 The shape & distribution of foliar lesions Shothole (Coryneum blight) fungus infects may give clues as to the type of pathogen tissue causing dead leaf tissue to drop out. Bacteria: if microscope Fungi: often round, across major available, check for streaming veins, concentric rings, diffuse borders Bacteria: water soaked initially, Fungi: check for angular limited by veins, yellow sporulation structures halo, may turn papery or into holes 33 36 6
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