Plant Diseases

    Plant Diseases

    Alfalfa Downy Mildew

    alfalfa stem nematode

    Downy mildew is an obligated parasite. Even though they look like fungi they are not. They belong to the Oomycota and are more closely realted to algae than true fungi.

    Alfalfa Stem Nematode

    alfalfa stem nematode

    Alfalfa stem nematode, Ditylenchus dipsaci, belongs to a diverse species of nematode often referred to as stem and bulb nematodes. Within this species are a number of races or strains of the nematode.

    Aspen, Important Pests of Ornamental Aspen


    Aspens are one of the more popular forest trees in the Intermountain West.  In an attempt to enjoy these beautiful trees around the home environment, many well-intentioned homeowners purchase or otherwise acquire aspens and transplant them into their landscapes.

    Barley Yellow Dwarf Virus (BYDV)


    Barley yellow dwarf virus (BYDV) is found worldwide. It infects small grains like barley, wheat, oats and rice as well as many wild grass species.  There are two strains of the barley yellow dwarf virus: BYDV-MAV and BYDV-PAV.

    Botrytis Neck Rot of Onion


    Botrytis neck rot is a post-harvest storage disease. It is caused by the fungi Botrytis aclada and B. allii. Infections occur in the field mainly through uncured necks but pathogen remains inactive until weeks later.

    Candidatus Liberbacter of Pepper

    candidatus liberbacter

    The non-culturable bacterium Candidatus Liberibacter solanacearum infects peppers. Bacteria are transmitted by potato psyllids, (Bactericera cockerelli). Bacteria are transmitted throughout the lifetime of the insect and can also infect tomatoes and potatoes.

    Coryneum Blight or Shothole

    coryneum blight

    Coryneum blight, also called shothole blight, is a fungal disease of stone fruit trees including peach, nectarine, apricot, cherry, and almond (ornamental as well as nut-bearing); however, the most commonly affected are apricot, peach, and nectarine.

    Curly Top of Tomato

    curly top

    Beet Curly Top Virus (BCTV) is taxonomically a Curtovirus in the Geminiviridae family of plant pathogenic viruses. It is vectored, or carried, by the beet leafhopper (BLH) insect. BCTV causes curly top of tomato, a comon disease in Utah and the western U.S.


    damping off

    Damping-off is caused by several soilborne fungi. The fungi thrive in wet conditions. Some have motile spores that can swim in water from root to root. It can easily be prevented by good sanitation and good cultural practices.

    Dothistroma Needle Blight


    Dothistroma needle blight is a fungal disease that occurs on a variety of coniferous trees. It is also known as "red band disease" in the western United States because of the distinct red banding symptoms that are produced.

    Fire Blight of Pears and Apples

    fire blight

    Fire blight is a bacterial disease of rosaceous plants. Economically, it is most serious on pears and apples. The bacterium that causes fire blight can be spread by insects, contaminated pruning or grafting tools, infected grafts, and any manner that carries the bacterial pathogen from an infected plant to one that is not.

    Fire Blight Annual Management Guide for Utah

    fire blight

    The popular Fuji, Gingergold, and Gala are more susceptible to fire blight. In addition, fire blight spreads more rapidly in high-density orchards.

    Intermountain Tree Fruit Production Guide

    tree fruit production guide

    Integrated pest management (IPM) involves collecting information about a pest and crop to ensure that you administer the most economical, effective, and environmentally and socially sound pest management decision.

    Iris Yellow Spot Virus in Onions

    iris yellow spot virus

    Iris Yellow Spot Virus (IYSV) is a damaging viral pathogen of onions. The disease can devestate an onion field by destroying the photosynthetic area of the leaves of infected plants, thus reducing the ability of the plant to develop bulb size and directly affecting yield and grade of onions at harvest.

    Necrotic Ring Spot

    necrotic ring spot

    Necrotic Ring Spot (NRS) is a fungal disease that primarily affects the roots of turfgrasses. The disease occurs on turfgrasses worldwide. Many turf species can serve as host to the disease.

    Necrotic Ring Spot and Summer Patch of Turfgrasses

    necrotic ring spot

    Necrotic ring spot and summer patch are two fungal diseases with similar above ground symptoms. Both pathogens mainly affect the root system and stolons of Kentucky bluegrass, annual bluegrass and tall fescue.

    Onion Powdery Mildew

    onion powdery mildew

    Onion powdery mildew is caused by Leveillula taurica, a fungal pathogen that has the ability to parasitize a very broad range of plant species. The pathogen can only grow on living host tissues and is thought to carry over from one season to the next on infected plant residue.

    Peach Leaf Curl

    peach leaf curl

    The disease is caused by the fungus Taphrina deformans. Disease is most severe during cool wet conditions. Foliage is susceptible until it is fully expanded. Infected leaves are distorted and discolored (yellow, red or sometimes purple).

    Pink Root Disease of Onions

    pink root

    The disease is caused by the fungus Phoma terrestris. Fungus is commonly found in soil. Infects roots but not basal plate or fleshy scales. Disease can get worse when onions are planted after cereals or in very short rotation with onion.

    Snow Mold on Small Grains

    snow mold

    Snow molds are diseases caused by fungi that attack small grain crops under snow cover or in cool, wet weather. There are three important types of snow mold fungi that can infect small grains in Utah and they can occur together on the same plant.

    Snow Mold on Turfgrass


    Snow molds are fungi that attack turfgrass under snow cover or in cool, wet weather. There are two different types of snow mold fungi that can infect grass and they can occur together on a plant.

    Spruce Health in Utah Landscapes

    spruce health

    Spruces tend to prefer abundant moisture and may not do well on droughty sites. Water stress caused by too little soil moisture or too much heat can predispose spruces to insect attack. 80% of spruce trees submitted to the UPPDL are diagnosed with stress due to abiotic conditions such as drought stress and deep planting.

    Streptomycin Resistance of Erwinia amylovora, Causal Agent of Fire Blight

    fire blight

    Fire blight is an important disease of apple and pear in Utah. Antibiotic streptomycin frequently used to control fire blight. Resistance to streptomycin first detected in 2006.

    Take-all Patch in Turf

    take all patch

    Take-all patch is a fungal disease of turfgrasses that primarily affects the roots of certain grass species. It has become a major disease of cool-season turfgrasses and can be found in many parts of the United States.

    The Backyard Orchard - Apple Pests


    The Backyard Orchard - Apricot Pests


    The Backyard Orchard - Cherry Pests


    The Backyard Orchard - Peach and Nectarine Pests


    The Backyard Orchard - Pear Pests


    The Backyard Orchard - Plum Pests


    Thousand Cankers Disease of Walnut

    thousand cankers

    Thousand cankers disease is caused by the fungus Geosmithia morbida. It is transmitted by the walnut twig beetle (Pityophthorus juglandis). Once symptoms are visible, trees can die within 2 to 3 years.

    Utah Home Orchard Pest Management Guide


    Integrated pest management (IPM) is the practice of combining knowledge of the pest and host plant with multiple tactics for long-term, safe pest control. The goal of IPM is pesticide reduction by using cultural, mechanical, and biological controls before the last option, pesticides.

    Wheat Stripe Rust

    wheat stripe

    Stripe rust, or yellow rust, is primarily a foliar fungal disease of wheat, although it can infect spike and stem tissues. If the pathogen infect the spike (head) it causes extensive quality and grain yield loss.

    Zebra Chip Disease of Potato

    zebra chip

    The non-culturable bacterium Candidatus Liberibacter solanacearum causes zebra chip disease of potatoes. Bacteria are transmitted by potato psyllids. Bacteria are transmitted throughout the lifetime of the insect and can also infect tomatoes and peppers.