Westcott's Plant Disease Handbook

Dr. Horst received his BS degree from Ohio University in Plant Science in 1957; his MS and Ph.D. degrees from Ohio State University in Plant Pathology in 1959 and 1962 respectively.  He was Director of the Plant Pathology Laboratory at Yoder Bros. in Barberton, Ohio, 1962-1968.  In 1968 he was appointed Assistant Professor of Plant Pathology at Cornell University.  He subsequently became Associate Professor in 1974 and Full Professor in 1980.  In addition to research, teaching and extension responsibilities, he also served as advisor for masters and doctoral students.  He has authored or co-authored more than 230 articles which include books, book chapters and invitational papers, and has guest lectured nationally and internationally. Horst wrote the 4th, 5th, 6th and 7th editions of Westcott's Plant Disease Handbook, the 1st edition of the Compendium of Rose Diseases, the Compendium of Chrysanthemum Diseases and the 2nd edition of the Compendium of Rose Diseases and Pests.  He is presently President and CEO of H&I Agritech, Inc., which develops biocompatible (environmentally safe) pesticides for disease and pest control.

Fraser Fir (Abis).- Root Rot (Phytophthora capsici).- Norway Maple (Acer platanoides).- Powdery Mildew (Sawadaii tulasnei).- Silver Maple (Acer saccharinum).- Bleeding Canker (Phytophthora cactorum and P. citricola).- White Snakeroot (Ageratina altissima).- Chlorotic Spots and Mosaic (Ag CSV) (Umbravirus).- Creeping Bentgrass (Agrostis stolonifera).- Foliar Blight (Colletotrichum cereale).- Onion (Allium cepa).- Iris Yellow Spot Virus (Family Bunyaviridae, Genus Tospovirus).- Onion (Allium cepa).- Twister Disease (Colletotrichum gloeosporium).- Alder (Alnus tenuifolia).- Alder Dieback (Valsa melanodiscus (Anamorph Cytospora umbriva).- Carolina Foxtail (Alopecurus carolinianus) Rice Blast Disease (Magnaporthe oryzae).- Bishop’s Weed (Ammi majus).- Apium Virus Y and Bidens Mottle Virus (Potyvirus).- Angelonia (Angelonia axgustifolia).- Yellow Mottling (Alternanthera Mosaic Virus Potexvirus).- Celery and Poison Hemlock (Apium graveolens and Conium maculatum).- Stunting and Chlorotic Line Patterns (Apium Virus Y, Potyviridae).- Peanut (Arachis hypogaea).- Sclerotinia blight (Sclerotinia sclerotiorum).- Peanut (Arachis hypogaea).- TWSV Potyvirus and CMV (Zuccinia Yellow Mosaic, Peanut Mottle and Peanut Stripe).- Peanut (Arachis hypogaea) Collateral Hosts Annual Weeds (Ipomoea hederacea, I. coccinea).- Stem Rot and Shredding (Sclerotinia minor).- Valencia Peanut (Arachis hypogaea).- Stem Rot (Sclerotinia sclerotiorum).- Pawpaw (Asimina triloba).- Sooty Blotch and Flyspeck (Colletogloeum sp., Dissoconium aciculare, Peltaster sp. P21, P. fructicola, Stomiopeltis versicola, Stomiopeltis sp. RS1, andDothiodeomycete sp. CS2.- Pawpaw (Asimina triloba).- Sooty Blotch and Flyspeck (Dissoconium aciculare, Peltaster sp. and Colletogloeum sp.).- Asparagus (Asparagus officinalis).- Spear and Root Rot (Phytophthora asparagi).- Sugar Beet (Beta vulgaris).- Yellowing Decline (Novel Fusarium Species).- Cabbage (Brassica oleracea).- Root Rot (Phytophthora drechsleri).- Turnip and Cabbage (Brassica rapa and B. oleracea).- Bacterial Leaf Spot (Xanthomonas campestris pv. campestris).- Turnip (Brassica rapa and other Brassicaceae including Arabidopsis thaliana).- Turnip Ringspot Virus (Comoviridae).- Buffalograss (Buchloe dactyloides).- Dollar Spot (Sclerotinia homoeocarpa).- Canna (Canna indica).- Mottling and Yellows (Canna Yellow Mottle Virus Family, Caulimoviridae).- Canna (Canna indica), Hosta (Hosta spp.), Peony (Paeonia spp.), Helleborus (Helleborus spp.), Diascia (Diascia spp.), Nemesia (Nemesia spp.).- Canna Yellow Mottle Virus (CaYMV), Hosta Virus X, Tobacco Rattle Virus (Peony), Helleborus Net Necrosis ‘Black Death Disease’ (Helleborus), Nemesia Ring Necrosis (Nemesia), Diascia Yellow Mottle, (Diascia), Tymovirus.- Chili Pepper (Capsicum annuum).- Fruit Set Failure (Novel Phytoplasma).- Pepper and Tomato (Capsicum annuum and Lycopersicum esculentum).- Little Leaf Phytoplasma (Phytoplasma asteris) (Aster Yellows Group).- Chile Pepper (Capsicum annuum).- Beet Mild Curly Top (Beet Mild Curly Top Curtovirus).- Orange Geiger (Cardia sebestena).- Tar Spot (Diatractium cordianum).- Papaya (Carica papaya).- Atypical Internal Yellowing (Enterobacter cloacae).- Bitternut Hickory (Carya cordiformis).- Annual Canker and Bitternut Decline and Death(Fusarium solani and Ceratocystis smalleyi).- Hackberry (Celtis occidentalis).- Angular Yellow Leaf Spot (Grapevine Leafroll-Associated Virus 3).- Diffuse Knapweed (Centaurea diffusa).- Crown Gall (Agrobacterium rhizogenes).- Common Lambsquarters (Chenopodium album).- Cyst Nematode (Cactodera milleri).- Chickpea (Cicer arietinum).- Powdery Mildew (Leveilula taurica).- Watermelon (Citrullus lanatus).- Fusarium Wilt (Fusarium oxysporum f. sp. niveum).- Cucurbits (Citrullus lanatus, Cucurbita pepo).- Stunt, Interversial Chlorosis, Leaf Mottling (Cucurbit Yellow Stunting Disorder, Begomovirus).- Citrus (Citrus spp.).- Greening Disease (Huanglongbing).- Citrus and Related Genera (Citrus spp. Murraya spp.).- Citrus Huanglongbing (HLB or Citrus Greening) (Candidatus L. asiaticus).- Coconut (Cocos nucifera).- Porroca; Hoja Pequeña (Little Leaf; Coconut Apical Necrosis).- Cilantro, Celery, Parsley (Coriandrum sativum, Apium graveolens, Petroselinum crispum).- Mosaic, Vein Clearing, Stunting (Apium Virus Y, Potyvirus).- Orange Geiger (Cordia sebestena).- Tar Spot (Diatractium cordianum).- Coreopsis (Coreopsis auriculata ‘Nana’).- Ornamentals Osteospermum fruticosum, Eustoma grandiflorum, and Gazania spp.- Lettuce Chlorotic Spots and Rings (LMV Potyvirus).- Melon (Cucumis sativus, C. melo, Citrullus lanatus).- Alternaria Leaf Spot (Alternaria alternata f. sp. cucurbitae).- Spaghetti Squash (Cucurbita maxima).- Leaf Necrosis and Twig Canker (Pseudomonas syringae and Pseudomonas marginalis).- Zucchini (Cucurbita pepo).- Cucurbit Leaf Curl (CuLCrV Begomovirus).- Cyclamen and Date Palm (Cyclamen persicum and Phoenix dactylifera).- Leaf Spot and Stem Lesions(Colletotrichum fragariae).- Bermudagrass (Cynodon dactylon).- Spring Dead Spot (Ophiosphaerella herpotricha).- Japanese Holly Fern (Cyrtomium falcatum).- Yellows, Mosaic, Necrosis, Ringspots (Holly Fern Mottle Virus HFMV).- Carnation (Dianthus caryophyllus).- Carnation Yellow Fleck and Necrotic Fleck (Closteroviridae).- Persimmon (Diospryros virginiana).- Flyspeck (Dissoconium mali).- Wild Rocket (Diplotaxis tenuifolia).- Leaf Spot (Xanthomonas campestris pv. raphani).- Purple Coneflower (Echinacea purpurea).- Phyllody (Candidatus Phytoplasma Asteris, subgroup 16Srl-B.- Coral Bean (Erythrina herbaceae).- Soybean Rust (Phakopsora pachyrhizi).- Fescue (Festuca rubra).- Smut (Urocystis agropyri).- Strawberry (Fragaria x anaassa).- Crown Rot (Macrophomina phaseolina).- Salal (Gaultheria shallon).- Anthracnose (Colletotrichum acutatum).- Soybean (Glycine max).- Soybean Rust (Phakopsora pachyrhizi).- Soybean (Glycine max).- Damping-off (Fusarium solani).- Soybean (Wild Soybean) (Glycine max subsp. soja).- Rust (Phakopsora pachyrhizi).- Soybean (Glycine max).- Rust (Phakopsora pachyrhizi).- Lettuce (Lactuca sativa).- Stunting, Necrotic Spotting, Leaf Chlorosis, Impatiens Necrotic Spot Virus (Bunyaviridae Family, Genus Tospovirus).- Bottle Gourd (Lagenaria siceraria).- Southern Blight (Sclerotium rolfsii).- Astragalus, Baptisia, Caragana, Cologania, Genista, Glycyrrhiza, Lathyrus, Pseudovigna, Robinia, Tephrosia, Teru - Soybean Rust (Phakopsora pachyrhizi).- Lettuce (Lactuca sativa).- Black Root Rot (Thielaviopsis basicola).- Lily (Lilium spp.).- Dwarfism, Shortened Internodes and Flower Abortion (‘Candidatus Phytoplasma Asteris Strains).- Tanbark Oak (Lithocarpus densiflorus).- Tanbark Oak Stem Cankers(Phytophthora ramorum, P. nemorosa, P. gonapodyides, P. cambivora, P. siskiyouensis, P. taxon ‘pgchlamydo’).- Tomato (Lycopersicon esculentum).- Leaf Curl (Tomato Yellow Leaf Curl Virus (Greenhouse Tomato).- Tomato (Lycopersicon esculentum).- Citrus Huanglongbing (HLB) (Candidatus Liberibacter asiaticus (dodder transmitted) (fastidious α-proteobacteria).- Black Medic (Medicago lupulina).- Branched Broomrape (Orobanche ramosa).- Alfalfa (Medicago sativa).- Spring Black Stem and Leaf Spot (Phoma medicaginis).- Alfalfa (Medicago sativa).- Brown Root Rot (Phoma sclerotioides).- Alfalfa (Medicago sativa).- Anthracnose (Colletotrichum trifolii, race 4).- Banana (Musa spp.).- Black Leaf Spot (Deightoniella).- Nemesia (Nemesia spp.).- Angelonia Flower Break (An FBV Carmovirus).- Rambutan (Nephelium lappaceum).- Fruit Rot (Pestalotiopsis virgatula).- Oleander (Nerium oleander).- Scorch, Defoliation, Branch Dieback, Short Internodes (Xylella fastidiosa).- Tobacco (Nicotiana tabacum).- Potato Necrotic Tuber Ringspot (Potato Virus Y NTN).- Ornamentals (4 new families and 1 additional genus within 3 others from Irrigation Water).- 6 New Phytophthora taxa: P. irrigate, P. hydropathical, DreII, CilI, CIP-like and Gon I.  New Orn. Fam. Apocynaceae, Asteraceae, Begoniaceae, Fabaceae; one additional genus within Ericaceae, Cucurbitaceae, and Solanaceae.- American Ginseng (Panax quinquefolius) Wilting/Damping-off, Black Stem (Phytophthora citricola).- Switchgrass (Panicum virgatum).- Bunt (Tilletia pulcherrima).- Switchgrass (Panicum virgatum).- Rust (Puccinia emaculata).- Avocado (Persea americana).- Laurel Wilt (Raffaelea sp.).-Beard-tongue (Penstemon digitalis).- Species in families: Brassicaceae, Cactaceae, Cucurbitaii, Leguminosae, Malvaceae, and Solanaceae.- Turnip Vein-clearing Virus (Red Foliar Ringspot, Penstemon Red Ringspot, PenRSV Tobamovirus.- Redbag (Persea borbonia).- Laurel Wilt (Raffaelea sp.).- Petunia (Petunia hybrida).- Powdery Mildew (Oidium longipes).- Beans (Phaseolus vulgaris).- Root Rot (Fusarium acuminatum, F. reddens).- Dry Bean (pints) (Phaseolus vulgaris).- Anthracnose (Colletotrichum lindemuthianum race 1153).- Spruce (Colorado White) (Picea pungens, P. glauca).- Needle Cast (Stigmina lautii).- Pine (Pinus spp.).-  White Rot (Amylostereum areolatum symbiont of Sirex noctilio (wood wasp).- Dryland Peas and Lentils (Pisum sativum and Lens culinaris).- Nematodes (Lesion – Pratylenchus neglectus, P. thornei, Pin – Paratylenchus hamatus).- Pea (Pisum sativum).- Pink Seed (Erwinia rhapontici).- Roughstalk Bluegrass (Poa trivialis).- Brown Ring Patch (Waitea circinata).- Poplar and Salix (Populus spp. and Salix spp.).- Overwintering Hosts for Melanospora spp.- Almond (Prunus dulcis).- Almont Band, Canopy Canker (Botryosphaeria dothidea).- Peach (Prunus persica).- Mottle, Ringspot, Line Patterns, Mosaic, Prunus Necrotic Ringspot).- Kudzu (Pueraria lobata).- Asian Soybean Rust (Phakopsora pachyrhizi).- Oak (Quercus cerris).- Endophytic Fungus (Climatic Factors –Modified Endophytic nature to weak Pathogenic Characteristics).- Rhododendion (Rhododendron catawbiense).- Twig Blight (Phytophthora hedraiandra).- Multiflora Rose (Rosa multiflora).- Cryptic Virus/Mild Symptoms (RMCV) Multiflora CrypticViruses, RNA 1 and 3).- Rose (Rosa multiflora).- Rose Spring Dwarf (RSDaV Luteroviridae).- Rhododendrum and Kalmia (Mountain Laurel) (R. catawbiensis and Kalmia japonica).- Necrotic Blighted Shoots and Blighted Necrotic Leaves (Phytophthora irrigata and P. hydropathica).- Blackberry (Rubus sp.).- Stunted and Crumbly Berry (Tobacco Ringspot Virus).- Blackberry (Rubus allegheniensis).- Shoot Blight Anthracnose (Glomerella cingulata).- Black Raspberry (Rubus canadensis).- Chlorosis, Mottling (Black Raspberry Necrosis Virus, Sadwavirus).- Canadian Blackberry (Smooth Blackberry) (Rubus canadensis).- Chlorosis, Vein Yellowing and Leaf Deformation (Marfivirus).- Red Raspberry (Rubus ideaus).- Rubus Yellow Net Virus (Genus, Badnavirus, Fam., Caulimoviridae).- Sugarcane (Saccharum officinarum).- Orange Rust (Puccinia kueknii).- Sesame (Sesamum indicum).- Leaf Spot and Seed Infection (Alternaria tenuissima).- Hairy Nightshade (Solanum sarrachoides).- Potato Leafroll Virus (Luteoviridae: Polerovirus, S. sarrachoides more efficient inoculums source than potato).- Potato (Solanum tuberosum).- Mild to Moderate Purple Top Syndrome (Phytoplasma 16Sr).- Potato (Solanum tuberosum).- Corky Ringspot (Tobacco Rattle Virus, Tobravirus).- Potato (Solanum tuberosum).- Potato Virus Strains (PVYNTN, PVYN:O).- Potato (Solanum tuberosum).- Foliar Blight and Tuber Rot (Phytophthora nicotianae).- Potato (Solanum tuberosum).- Corky Ringspot (Tobacco Rattle Virus, Tobravirus).- Sugarcane (Saccharum officinarum).- Rust (Puccinia kueknii).- Eugenia/Brush Cherry (Syzygium paniculatum).- Dieback (Botryosphaeria-like fungi including Fusicoccum, Neoscytalidium and Botryosphaeria).- Crepe Jasmine (Tabernaemontana manilensis).- Rust (Uredo manilensis) (Telial Stage P. manilensis).- Wheat and Barley (Triticum aestivum and Hordeum vulgare).- Cyst Nematode (Heterodora filipjevi).- Wheat (Triticum aestivum).- Triticum Mosaic – TriMV (Tritimovirus Potyviridae).- California Laurel (Umbellularia californica) Also: Sassafras albidum and avocado (Persea americana).- Laurel Wilt (Raffaelea lauricola).- Blueberry (Vaccinium corymbosum).- Leaf Rust (Pucciniastrum corymbosum).- Leaf Spot; Twig Blight (Nigrospora sphaerica).- Viburnum and Osmanthus (Viburnum tinus, Osmanthus heterophyllus, O. fragrans.- Sudden Oak Death (Phytophthora ramorum).- Mung Bean (Vigna radiata).- Brown-to-Reddish Brown Lesions-Sprouts (Rhizoctonia solani).- Toad Lily (Tricyrtis formosana).- Tricyrtis Virus Y and Lily Virus X (TrvY and LVX Potexvirus).- Wheat (Triticum aestivum).- Stunting (Cyst Nematode, Heterodera filipjevi).- Corn Salad or Lamb’s Lettuce (Valerianella locusta).- Downy Mildew (Peronospora valerianellae).- Orchids (Vanda spp.).- Bacterial Soft Rot (Erwinia chrysanthemi) (Dickeya chrysanthemi).- Grape (Vitis vinifera).- Bot Canker Disease (Lasiodiplodia theobromae and Diplodia seriata).- Grape (Vitis vinifera).- Fanleaf Degeneration Disease.- Grapevine Fanleaf Virus (Genus Nepovirus, Family Comoviridae).- Grape (Vitis vinifera).- Sour Rot (Aspergillus carbonarius).- Grapevine Fanleaf (Grapevine Fanleaf Virus: Genus Nepovirus Family: Comoviridae).- Grapevine Leafroll Disease (GLRaV-9).- Wisteria (Wisteria sinensis).- Mosaic (Wisteria Vein Mosaic Virus).- Maize (Zea mays).- Leaf Stripe, Stem Rot (Burkholderia gladioli).-Maize and Sorghum (Zea mays and Sorghum bicolor) onion in U.S..- Leaf Blight and Vascular Wilt (Pantoea agglomerans).- Zoysiagrass (Zoysia matrella; Z. japonica).- Foliar Blight (Curvularia lunata).- Zoysiagrass (Zoysia matrella).- Blight (Curvularia lunata (C. pallescens?).