Recognizing and Managing Blueberry Diseases

Transcription

1 Recognizing and Managing Blueberry Diseases 2016 Mississippi Blueberry Education Workshop Hattiesburg, Mississippi January 14, 2016 Rebecca A. Melanson, Extension Plant Pathologist Central MS Research and Extension Center Raymond, MS

2 Plant Pathology 101 What factors and conditions are necessary for disease development?

3 The Disease Triangle Three conditions are necessary for disease development. VIRULENT PATHOGEN bacteria, fungi, viruses, nematodes SUSCEPTIBLE HOST species, cultivar/variety, tissue (type, age) If any ONE of these conditions is ABSENT, disease will NOT develop. FAVORABLE ENVIRONMENT temperature, moisture, etc. VIRULENT PATHOGEN NO DISEASE FAVORABLE ENVIRONMENT SUSCEPTIBLE HOST

4 How is the Disease Triangle important for disease management? The Disease Triangle VIRULENT PATHOGEN bacteria, fungi, viruses, nematodes Disease management aims to modify one of the components in the Disease DISEASE Triangle so that disease development does not occur. FAVORABLE ENVIRONMENT temperature, moisture, etc. SUSCEPTIBLE HOST species, cultivar/variety, tissue (type, age) VIRULENT PATHOGEN SUSCEPTIBLE HOST FAVORABLE ENVIRONMENT

5 General Disease Management Strategies Always begin with healthy (disease-free) plants! Choose appropriate varieties. Grow varieties suitable for your area. If available, choose varieties that have disease resistance. Choose a proper planting site! Consider drainage, sunlight exposure, and air circulation. Practice good sanitation. Use proper cultural practices. Cultivation, pruning, weed control, plant health maintenance Apply pesticides.

6 How can YOU be prepared to manage diseases? Know your plant! Know and be able to recognize the diseases that can occur. Be observant! Scout regularly for disease. Keep records. Know where to find information about diseases. Resources! Know what information to collect. Know who to contact for help.

7 The first step in disease management is DIAGNOSIS. Identify the cause of the symptoms! Management methods depend on the pathogen and what we know about its biology/life cycle. Photo: P. Bachi, U. of KY Research and Education Center, Bugwood.org Photo: R. A. Melanson, MSU Extension

8 Can YOU identify diseases? What do you look for? Where do you look? How can you recognize disease?

9 Can YOU identify blueberry diseases? Leaf rust Iron deficiency Mummy berry Photo: J. Hartman, University of Kentucky, Bugwood.org Powdery mildew Photo: University of Georgia Plant Pathology, University of Georgia, Bugwood.org Photo: Bruce Watt, University of Maine, Bugwood.org Stem canker (Botryosphaeria) Photo from APS Compendium of Blueberry and Cranberry Diseases Cold damage Photo from MS Fruit and Nut Blog by Eric Stafne, Photo from The NC Blueberry Journal,

10 Botryosphaeria Stem Canker Caused by a fungus Symptoms Small red lesions on stems develop into cankers Stems may become girdled and die Fungus infects current season s growth in late spring, but disease can progress into older tissues Wet conditions and temperatures between 77-82ºF are optimal for spore production. Infection process can occur within 24 hours Disease can become more severe each year Photo: G. Holmes, Cal Poly (San Luis Obispo), Bugwood.org

11 Botryosphaeria Stem Blight (Dieback) Caused by a fungus Symptoms Yellowing, reddening, and drying of leaves *Dead branch or branches Light brown leaves remain attached to plant Discoloration of woody tissue (often on one side) Most infections occur from May to June Symptoms appear 4-6 weeks after infection Infection occurs through wounds - *pruning, other mechanical injury, stem cankers Photo from /fdin009/fdin009.htm

12 Botryosphaeria Stem Canker and Stem Blight Use disease-free planting stock Remove dead tissue Remove and destroy cankers/infected stems Fungicides are generally ineffective *Avoid wounding plants Photo from uit/fdin009/fdin009.htm

13 Mummy Berry Caused by a fungus Symptoms Spring: Drooping of leaves and shoots followed by discoloration and death of infected foliage Affected tissues eventually fall from the plant Tan to gray tufts on blighted shoots At ripening: Infected berries turn cream to salmon pink and eventually tan/white/gray; soft at first but shrivel and harden (mummies) Mummified berries drop to the ground Photo: University of Georgia Plant Pathology, University of Georgia, Bugwood.org

14 Mummy Berry Fungus overwinters in mummified fruit on the ground Mummies may survive in the soil for several years Fungal spores may be disseminated via wind, rain, or insects Developing tissues exposed to frost injury are most susceptible Photo: University of Georgia Plant Pathology, University of Georgia, Bugwood.org

15 Mummy Berry Practice sanitation Cultivate Removal of mummies Prune frost-injured canes Use resistant cultivars, if available Apply fungicies Photo: University of Georgia Plant Pathology, University of Georgia, Bugwood.org

16 Anthracnose Fruit Rot (Ripe Rot) Caused by a fungus Symptoms Blighting of blossoms Fruit asymptomatic until maturity when blossom-end becomes soft and sunken; salmon-colored spores may become visible Leaf spots or twig lesions possible Fungus overwinters in and on blighted twigs Spores released during rains throughout growing season All fruit (all stages) is susceptible to infection Losses more severe during prolonged periods of warm, wet weather during bloom and before harvest Photos from Midwest Blueberry Production Guide

17 Anthracnose Fruit Rot (Ripe Rot) Use resistant cultivars* Harvest fruit often and as it ripens Rapid post-harvest cooling to inhibit postharvest rot Apply fungicides Photos from Midwest Blueberry Production Guide

18 Botrytis Blossom Blight and Fruit Rot Caused by a fungus Symptoms Twigs are initially brown/black but become tan/gray Abundant gray mycelium and spores develop on blighted blossoms Fruit rots can occur after harvest Typically causes losses early in the growing season Infects tender growth (green twigs, blossoms, leaves, fruit) Can cause severe damage with rainy weather through bloom Fungus overwinters in or on plant debris or as sclerotia Spores produced in spring move easily by wind Photos from

19 Botrytis Blossom Blight and Fruit Rot Management Use practices that promote air movement in plant canopy Avoid excessive use of nitrogen fertilizer in spring Harvest fruit often and as it ripens Rapid post-harvest cooling to inhibit post-harvest rot Apply fungicides Photos from

20 Septoria Leaf Spot and Stem Canker Caused by a fungus Symptoms White/tan spots with reddish-purple borders with dark spore-producing structure in center of spot Purple lesions on stems that eventually become lighter in color Leaf spots develop in early May and then can increase rapidly Most severe in cuttings and young plants Fungus overwinters in leaf debris and infected stems Management Remove or cultivate leaf debris Apply fungicides Photo from mposium/melhus/septoria/

21 Exobasidium Fruit and Leaf Spot Caused by a fungus Symptoms Green, unripe spots on fruit when ripe Light green leaf spots on upper side of leaf that are white are the underside of the leaf Leaf spots become brown and necrotic with time Photos from UGA Blueberry Blog by Phil Brannen,

22 Blueberry Leaf Scorch Caused by a bacterium First reported in 2004 (Georgia) Symptoms Marginal scorching progressing towards necrosis and leaf drop Yellowing of stems Plant death Management Do not propagate from diseased plants Remove/destroy infected plants (?) Vector management (?) Photos from bacterial-leaf-scorch-of-blueberry (left) and caes.uga.edu/extension/documents/blueberryxylella.pdf (right)

23 Viruses in Blueberry Shoestring virus Leaf mottle virus Red ringspot Blueberry mosaic Photo credits (left to right): Mark Longstroth, Michigan State University; Michigan State University; The NC Blueberry Journal, and UK - Diseases of Fruit Crops and Ornamentals blog by Nicole Ward,

24 Resources Mississippi State University Extension MSU Plant Disease and Nematode Diagnostic Services The Southern Region Small Fruit Consortium Clemson, NC State University, Virginia Polytechnic Institute and State University, University of Arkansas, University of Georgia, University of Tennessee

25 Southeast Regional Integrated Management Guide

26 Southeast Regional Integrated Management Guide 2016 Edition Coming Soon! Arranged by plant stage Provides: Description of diseases Management options Rates Effectiveness of management option against that disease Re-entry intervals Post harvest intervals Additional comments

27 Thank you for your attention! Rebecca A. Melanson Extension Plant Pathologist vegetables, fruits, and nuts Contact Information: Central Mississippi Research and Extension Center 1320 Seven Springs Road Raymond, MS Phone: (601) Photo by MSU Extension Service