Plant Disease Outbreak Seasonal Calendar

The Apple Maggot (Rhagoletis pomonella), a highly destructive fruit-infesting fly larva belonging to the fruit fly family Tephritidae under the order Diptera, is a major economic pest of apples and various pome fruits across North America.

Apple scab is arguably the most economically significant fungal disease affecting apple trees (Malus domestica) and ornamental crabapples worldwide. Caused by the ascomycete fungus Venturia inaequalis, this disease primarily targets the foliage and the developing fruit, leading to significant yield loss and reduced fruit quality.

Bacterial Canker (caused primarily by the gram-positive bacterium Clavibacter michiganensis in tomatoes, and Pseudomonas syringae in stone fruit trees) is a highly destructive, contagious bacterial disease capable of causing total crop f...

Bacterial Spot is a highly destructive and economically devastating plant disease caused by several species of gram-negative bacteria in the genus Xanthomonas (most notably Xanthomonas euvesicatoria and Xanthomonas perforans).

Bacterial Wilt, primarily caused by the soil-borne pathogen Ralstonia solanacearum, is a highly destructive and economically devastating vascular disease affecting a wide range of host crops, most notably Solanaceous plants like potatoes...

The Bagworm (Thyridopteryx ephemeraeformis), a highly unique foliage-chewing caterpillar belonging to the family Psychidae under the order Lepidoptera, is a major pest of ornamental and forest evergreen trees across North America.

Black Spot (Diplocarpon rosae or Marssonina rosae), a highly prevalent and damaging fungal disease belonging to the order Helotiales of the phylum Ascomycota, is the single most destructive foliar disease affecting roses (Rosa spp.) worl...

Botrytis cinerea (commonly known as grey mold or noble rot) is an aggressive, necrotrophic airborne fungus belonging to the phylum Ascomycota. It targets an exceptionally broad range of plant hosts—exceeding 200 species globally—disrupting both outdoor agricultural crops and greenhouse nurseries.

Brown rot is one of the most common and devastating fungal diseases affecting stone fruits globally, caused primarily by the pathogens Monilinia fructicola and Monilinia laxa.

The Cabbage Worm (primarily Pieris rapae, also known as the imported cabbageworm) is the larval stage of the common small white butterfly, belonging to the family Pieridae of the order Lepidoptera.

Cedar-Apple Rust is a highly specialized and economically damaging heteroecious fungal disease caused by the Basidiomycete pathogen Gymnosporangium juniperi-virginianae.

Cercospora Leaf Spot is a highly destructive and economically significant fungal plant disease caused by various host-specific species in the anamorphic genus Cercospora (most notably Cercospora beticola on sugar beets, and Cercospora so...

Clubroot, caused by the soil-borne protist pathogen Plasmodiophora brassicae, is an aggressive, persistent, and highly destructive root disease that exclusively targets plants in the mustard family (Brassicaceae), including cabbage, caul...

The Cotton Bollworm (Helicoverpa armigera), belonging to the owlet moth family Noctuidae under the order Lepidoptera, is one of the most destructive agricultural pests in the world.

Crown gall is a unique, tumor-inducing bacterial plant disease caused by the soil-borne bacterium Agrobacterium tumefaciens (family Rhizobiaceae). It is highly famous in molecular biology for its natural ability to 'genetically engineer' host plants by physically transferring a piece of its own DNA (the Ti plasmid) into plant cell nuclei.

Cutworms, belonging primarily to the owlet moth family Noctuidae under the order Lepidoptera, are among the most registered seedling pests in agriculture.

Damping off is a devastating disease complex caused by a group of soil-borne oomycetes and fungi (primarily Pythium spp., Rhizoctonia solani, and Fusarium spp.) that targets newly germinated seeds and young seedlings.

Downy mildew refers to a highly destructive group of plant diseases caused by specialized oomycetes, or water molds, within the family Peronosporaceae.

Dutch Elm Disease (DED), caused by the highly aggressive ascomycete fungi Ophiostoma ulmi and the even more virulent Ophiostoma novo-ulmi, is a catastrophic, highly lethal vascular wilt disease that has devastated elm (Ulmus spp.) tree p...

Early blight is a highly prevalent and damaging fungal disease caused by Alternaria solani (and sometimes Alternaria tomatophila), primarily targeting members of the Solanaceae (nightshade) family.

Ergot is a highly specialized and historically infamous plant disease caused by the obligate biotrophic ascomycete fungus Claviceps purpurea. This pathogen attacks cereal crops—particularly rye, wheat, triticale, barley, and various forage grasses—replacing healthy grain seeds with dark, toxic fungal structures.

Fire Blight, caused by the highly contagious Gram-negative bacterium Erwinia amylovora, is a destructive, potentially lethal systemic disease that targets pome fruits, particularly apples, pears, quinces, and other members of the rose fa...

Fungus gnats (superfamily Sciaroidea, primarily families Sciaridae and Mycetophilidae) are small, delicate, dark-bodied insects resembling miniature mosquitoes.

Fusarium Head Blight (FHB), also widely known as scab or tombstone rot, is a highly destructive fungal disease caused primarily by the ascomycete pathogen Fusarium graminearum (teleomorph Gibberella zeae).

Fusarium Wilt is a highly destructive, soil-borne fungal disease caused by the species complex Fusarium oxysporum. This notorious ascomycete pathogen is unique because it consists of hundreds of host-specific strains, called formae speci...

Lace Bugs (family Tingidae), comprising numerous specialized sucking insect species within the genus Corythucha, are widespread foliar pests that target a variety of deciduous trees and ornamental shrubs.

Leaf miners are not a single species, but the larval stage of various insect groups, most commonly tiny flies belonging to the family Agromyzidae (such as Liriomyza spp.), as well as certain moths and beetles.

Loose smut is a serious seed-borne fungal disease caused primarily by Ustilago tritici in wheat and Ustilago nuda in barley. Unlike many other plant diseases that affect leaves or stems, loose smut is a systemic infection that remains dormant inside the seed embryo.

The Parsley Worm (Papilio polyxenes), which represents the active larval caterpillar stage of the beautiful Eastern Black Swallowtail butterfly (family Papilionidae, order Lepidoptera), is a specialized foliar-chewing herbivore pest that...

The Pink Bollworm (Pectinophora gossypiella) is one of the most destructive and economically devastating insect pests of cotton (Gossypium) crops worldwide, especially in cotton-growing belts of India, China, and the Americas.

The Plum Curculio (Conotrachelus nenuphar), a highly destructive fruit-infesting snout beetle (weevil) belonging to the family Curculionidae under the order Coleoptera, is a premier pest of stone and pome fruits across eastern North Amer...

Powdery Mildew (order Erysiphales, primarily families Erysiphaceae), a highly widespread and recognizable fungal disease belonging to the class Leotiomycetes of the phylum Ascomycota, is a major threat to agricultural, greenhouse, and ho...

Psyllids, commonly known as jumping plant lice, are small, sap-sucking insects belonging to the superfamily Psylloidea under the order Hemiptera. These active plant pests are major agricultural threats across multiple crop families, particularly the Asian Citrus Psyllid (Diaphorina citri) and pear psylla (Cacopsylla pyricola).

Root-knot nematodes (Meloidogyne spp.) are microscopic, soil-dwelling roundworms that represent one of the most significant and difficult-to-manage threats to global agriculture.

Root Rot, caused by a diverse complex of soil-borne oomycete and fungal pathogens (most notably Phytophthora spp. and Pythium spp. of the family Peronosporaceae, alongside fungal genera like Rhizoctonia and Fusarium), is a devastating, potentially lethal soil-borne disease affecting virtually all container and field crops.

Rust Disease (caused by obligate biotrophic fungi in the order Pucciniales, primarily genera Puccinia and Uromyces) is a highly prevalent and economically damaging fungal leaf infection affecting thousands of plant species worldwide.

San Jose Scale (Comstockaspis perniciosa, historically Quadraspidiotus perniciosus), an armored scale insect belonging to the family Diaspididae in the order Hemiptera, is a severe, highly destructive sap-sucking pest that targets stone ...

Sawflies are a primitive group of insects belonging to the suborder Symphyta, closely related to wasps, bees, and ants but distinguished by the absence of the characteristic 'wasp-waist' constriction.

Scale insects are small, sap-sucking pests belonging to the superfamily Coccoidea, comprising over 8,000 described species. They are unique among garden pests because adult females are generally immobile and covered by a waxy or armored shell, often causing them to be mistaken for fungal growths, galls, or inanimate bumps on stems and leaves.

Septoria Leaf Spot, caused by the destructive ascomycete fungus Septoria lycopersici, is one of the most common, aggressive, and economically damaging foliar diseases of tomatoes (Solanum lycopersicum) and other Solanaceous crops.

Snails and slugs are soft-bodied terrestrial mollusks belonging to the class Gastropoda. Unlike true insects, these pests are closely related to clams and octopuses.

The Spotted Lanternfly (Lycorma delicatula), belonging to the planthopper family Fulgoridae under the order Hemiptera, is a highly invasive and economically damaging sucking pest native to China, India, and Vietnam.

Stem rust, also known as black rust or cereal rust, is a devastating fungal disease caused by the pathogen Puccinia graminis. It is historically one of the most destructive diseases of cereal crops worldwide, capable of turning a healthy-looking crop into a tangle of black, shriveled stalks and empty heads in a matter of weeks.

The Stink Bug (family Pentatomidae, featuring highly notorious invasive species like the Brown Marmorated Stink Bug, Halyomorpha halys) is a major, highly widespread sucking insect pest belonging to the order Hemiptera.

Sudden Oak Death (SOD), caused by the aggressive oomycete (water mold) pathogen Phytophthora ramorum, is a highly destructive, lethal tree epidemic that has devastated oak and tanoak forests in coastal California and Oregon.

Tar Spot of Maple, caused primarily by the specialized ascomycete fungus Rhytisma acerinum, is a common, highly conspicuous foliar disease that targets various species of maple trees (Acer spp.).

Tikka Disease (Groundnut Leaf Spot), primarily caused by the fungal pathogens Cercospora arachidicola (early leaf spot) and Cercosporidium personatum (late leaf spot), is the most prominent and economically destructive foliar disease aff...

Verticillium Wilt is a highly destructive soil-borne fungal disease caused by the ascomycete pathogens Verticillium dahliae and Verticillium albo-atrum.

The White Grub (primarily Holotrichia spp. and other scarab genera) is a highly destructive soil-dwelling insect pest representing the larval stage of scarab beetles, June bugs, or chafers belonging to the beetle family Scarabaeidae.

White Mold, caused by the notorious soil-borne Ascomycete fungus Sclerotinia sclerotiorum, is a highly destructive, cosmopolitan plant disease affecting over 400 species, mostly broadleaf crops.

White Rust of crucifers, also known as white blister, is a destructive plant disease caused by the specialized Oomycete pathogen Albugo candida (not a true fungus, but a water mold).

The Wireworm (primarily Agriotes spp.) is a highly destructive soil-dwelling agricultural insect pest representing the larval stage of click beetles belonging to the beetle family Elateridae.

Yellow Rust, also widely known as Stripe Rust, is a devastating airborne fungal disease caused by the obligate biotrophic basidiomycete pathogen Puccinia striiformis.