Reading: Dreistadt et al.. 2004 - p. 21-48, 212-222; 349-472 Agrios Chapter 9

1. Lecture 19 PRINCIPLES OF DISEASE MANAGEMENT Reading: Dreistadt et al.. 2004 - p. 21-48, 212-222; 349-472 Agrios Chapter 9 PNW Plant Disease Management Handbook

3. Disease management (control)From PNW Plant Disease Management Handbook Exclusion – quarantines, inspections, certification Avoidance – not planting in poorly drained soils (Phytophthora), avoiding wounding Eradication – crop rotation, sanitation, eliminating alternate hosts, fumigation Protection – treating healthy plants before infection - fungicides Resistance – genetic resistance – tolerance, immunity

4. PRINCIPLES OF DISEASE MANAGEMENT • CULTURAL • CHEMICAL • GENETIC - BREEDING FOR RESISTANCE/ BIOTECHNOLOGY • BIOLOGICAL CONTROL • QUARANTINE • DOING NOTHING

5. 1. CULTURAL Practices for producing healthy plants Improved growing conditions – fertilization, soil organic matter, good drainage, avoid compaction Host removal Inoculum reduction – removal of stumps and roots for root diseases, raking and removal of infected leaves Pruning, thinning Crop rotation Sanitation – debarking for Dutch elm disease, leaf raking Use of alternative species – red cedar for laminated root rot Mulches - polyethylene tarps, bark, wood chips Suppressive soils/antagonism of other microbes Antagonistic plants - mustard Physical methods – heat (black or clear plastic, steam), light, refrigeration

6. Verticillium wilt – Japanese maple

7. Rose Powdery Mildew and Common Cultural Methods for Control Powdery Mildew (Sphaerotheca pannosa) • Overwinters in infected buds, canes and fallen leaves and attacks young spring growth. • Thrives in areas with high relative humidity at night when temperatures are around 60 degrees F. • Also thrives at around 80 degrees F with 40%-70% RH. Best way to prevent powdery mildew and other diseases w/o using chemicals! • Clean up fallen leaves, deadheads and other debris. DO NOT COMPOST! • Allow adequate space for plants when planting to ensure good air circulation. • Avoid overwatering, overhead watering, and applying too much fertilizer. • Plant “resistant” varieties

9. 2. CHEMICAL METHODS Fungicides Fumigants – methyl bromide, chloropicrin (still looking for alternative to MB) Control of insect vectors – e.g., Dutch elm disease

10. Fungicide application to control ergot on rye

12. Agriculture fumigation Forest nursery fumigation Ethanedinitrile – MB alternative

13. Fumigant application methods

14. FUNGICIDES Classified by chemical class or mode of action or by properties once in the plant. a. Chemical class – organic or inorganic - best to mix or rotate materials found in different fungicide families.

15. b. Mode of action and properties in the plant (terms) Antibiotics - Streptomycin against fire blight Biofungicides – Trichoderma harzianum, Pseudomonas syringae, Bacillus subtilis, Verticillium dahliae Broad spectrum - captan, sulfur Narrow spectrum - metalaxyl against Phytophthora Broad to narrow spectrum

16. Bactericidal Curative - generally act within the plant and are effective shortly after penetration Demethylation-inhibiting - funginex Eradicant (contact killing, prevent sporulation) Fungicidal - kills fungi - Captan Fungistatic - inhibit fungi (metalaxyl) Fumigant - vapor action (methyl bromide) Nematicide Protectants - prevent spores from germinating - Bravo Systemic - usually absorbed by roots and translocated through plant (metalaxyl) some move downward (Aliette - stimulates host defense mechanisms) Locally systemic - don't move far in the plant – Thiophanate methyl Vapor action - fumigants

17. c. Common fungicides in the home landscape(multiple modes of action) Captan - broad spectrum - leaf spots, blights (not good against powedery mildews and rust) Chlorothaninol (Daconil 2878, Fung-onil, Bravo) - broad spectrum. Foliar treatment Copper based compounds (Bordeaux mix , copper sulfate) downy mildew on grapes, many fungal and bacterial leaf diseases and cankers Horticultural and botanical oils (Neem oil, pesticidal oil) – good eradicants – powdery mildew

18. Lime sulfur or calcium polysulfide (Lime sulfur) - eradicant and dormant spray - powdery mildew, scab, brown rot, leaf curls, rusts and mites - can burn Mancozeb (Greenlight broad spectrum) – fungal diseases - lawns, fruits, vegetables, ornamentals Mycobutanil (Immunox, Spectricide) – powdery mildews,rusts, leaf spots PCNB (pentachloronitrobenzene) - soil fungicide – lawn snow mould Soaps (Safer’s Insecticidal Soap) – powdery mildews Sodium or Potassium bicarbonates – not very effective

19. Streptomycin (Fire Blight Spray) Sulfur (Safer’s Garden Fungicide) - elemental sulphur - powdery mildew and leaf blights - can burn Thiophanate methyl (Green Light Systemic Fungicide) - ornamentals, lawns, some fruit trees Triforine (Funginex) - locally systemic - powdery mildews, leaf spots, blights   Compost tea – foliage diseases. Does it work? Fungicides may also need spray adjuvant to work - stickers, etc.

20. Rhododendron - Phytophthora root disease How to treat?

21. 3. BREEDING FOR RESISTANCE/ BIOTECHNOLOGY Resistant species and varieties, molecular techniques - gene transfer

22. Resistant cherry in Arboretum?

23. 4. BIOLOGICAL CONTROL With antagonistic fungi and bacteria, mycorrhizae, antibiotics Fungi Trichoderma harzianum, Verticillium dahliae Bacteria Pseudomonas syringae, Bacillus subtilis

24. BIOLOGICAL CONTROL MYCORRHIZAE Mycorrhizae (fine root/fungal muutalistic symbiotic association) - Fungus protects plants against pathogens Mix of ectomycorrhizae and arbuscular mycorrhizae

25. Phytophthora lateralis in the Arboretum Success story for mycorrhizas?

26. Biological control of Dutch elm disease Dutch Trig A suspension of live spores of the fungus Verticillium dahliae injected into the tree by gouge pistol. Protects by inducing resistance in the tree Pros Small injection holes, rapid, less costly than fungicide Cons Must be applied every year V. dahliae is a plant pathogen Only an option before infection

27. 5. QUARANTINE Excluding diseased plants, seeds, bulbs or contaminated soil, machinery, etc. Introduced pathogens Sudden oak death

28. SUDDEN OAK DEATH Controlled largely by quarantine and plant destruction The current host list includes: California black oak, coast live oak, Shreve oak, tanoak, rhododendron, California bay laurel, big leaf maple, madrone, manzanita, huckleberry, California honeysuckle, toyon, California buckeye, California coffeeberry, Douglas-fir and coast redwood and Arrow wood (in Germany, the United Kingdom, and the Netherlands).

29. 6. DOING NOTHING How much disease are you prepared to handle? Decay in trees could provide wildlife habitat, but could allow development of hazard trees

30. PNW Plant Disease Management Handbook For each host • Cause • Symptoms • Cultural control • Chemical control • References

31. Cherry brown rot in Arboretum

32. Brown rot mummies

33. Cherry brown rot • Cause – two fungal species (Monilinia fructicola and M. laxa) incites blossom blight, twig and branch dieback, fruit rot of ornamental and fruit trees – cherries, peaches, nectarines, prunes, plums, almonds and apricots. More of a problem west of Cascade crest. Wind and rain blow ascospores and conidia to healthy blossoms in spring from mummies.

34. Cherry brown rot continued. Symptoms • Infected flower parts turn light brown or gray; water soaked flowers; branch girdling; profuse gumming; fruit symptoms dark spots with buff-colored spores

35. Brown rot continued Cultural control • Remove and control infected twigs and branches a • Remove and destroy mummified fruit • Use moderate amounts of N fertilizer

36. Brown rot continued Chemical control • Apply fungicides during the bloom period at early popcorn, full bloom, and/or petal fall with alternate fungicides • 26 different fungicides are available Captan 80 WDG ar1.9 to 2.5 lbs/acre Fixed copper for blossom blight only Wettable sulfur