Common Diseases: Leaf spots and blights categories: Common Diseases Common Problems revision date: 2022-11-04 01:09 Madrone leaf spotsPhoto by: R.S. Byther Biology Leaf spots are localized lesions on host leaves consisting of dead and collapsed cells. Blights are general and extremely rapid browning of leaves, branches, twigs and floral organs resulting in their death. Leaf […]
Common Diseases: Nectria cankers categories: Common Diseases Common Problems revision date: 2022-11-04 11:40 Nectria canker fruiting bodies on branchPhoto by: R.S. Byther Biology Nectria canker is a fungal disease affecting the twigs and branches of a wide variety of woody plants, including pear, maple, and apple (where it is called European canker). The fungus infects […]
Common Diseases: Phytophthora root rot categories: Common Diseases Common Problems revision date: 2022-11-04 11:32 Phytophthora collar rot on madronePhoto by: R.S. Byther Biology Phytophthora root rot is caused by a fungal infection of the roots resulting in root death and overall plant decline. Infected plants may appear off-colored and stunted and may show symptoms of […]
Common Diseases: Powdery mildew categories: Common Diseases Common Problems revision date: 2022-11-04 11:23 Powdery mildew infections on begonia leavesPhoto by: R.S. Byther Biology White powdery growth on the surface of leaves and sometimes stems is characteristic of this easily diagnosed fungal disease. Young leaves and shoots may be stunted and distorted. Severe infections can cause […]
Common Diseases: Pseudomonas bacterial canker categories: Common Diseases Common Problems revision date: 2022-11-04 10:54 Bacterial canker on tree trunkPhoto by: R.S. Byther Biology Pseudomonas bacteria remain alive in old cankers, in buds, and on plant surfaces of infected trees and on many kinds of plants, including weeds and grasses. Bacteria may be systemic within the […]
Common Diseases: Root rots categories: Common Diseases Common Problems revision date: 2022-11-04 10:49 Pansies dying from Rhizoctonia root rotPhoto by: R.S. Byther Biology Many different fungi that infect root tissues cause similar symptoms: off-color foliage, stunting, wilting, and death. Laboratory isolation and microscopic examination are needed for specific diagnosis. Cylindrocladium, Fusarium, Rhizoctonia, and Pythium are […]
Common Diseases: Rusts categories: Common Diseases Common Problems revision date: 2022-11-04 10:43 Hypericum rust fruiting bodies on underside of leavesPhoto by: R.S. Byther Biology In general, rust diseases are easily diagnosed because of the abundant production of colorful powdery spores formed in tiny pustules. Microscopic examination may be necessary to identify specific rust pathogens. Spore […]
Common Diseases: Sclerotinia white mold categories: Common Diseases Common Problems revision date: 2022-11-04 10:32 Rotted petunia stem with sclerotia insidePhoto by: R.S. Byther Biology Sclerotinia white mold is a fungal disease affecting many herbaceous flowers and vegetable crops. A stem rot and white fungal growth appear at the base of infected plants. Infected plants wilt […]
Common Diseases: Sudden oak death categories: Common Diseases Common Problems revision date: 2022-11-04 09:58 P. ramorum shoot blight symptoms on rhododendronPhoto by: M. Elliott Biology Sudden Oak Death (SOD) is the common name for a disease caused by Phytophthora ramorum, a previously unknown and exotic plant pathogen. In California, it has killed hundreds of thousands […]
Common Diseases: Tubercularia canker categories: Common Diseases Common Problems revision date: 2022-11-04 09:45 Tubercularia canker fruiting bodiesPhoto by: R.S. Byther Biology Tubercularia canker is a fungal disease typically affecting twigs and branches, and occasionally trunks, of several species including elm, Russian olive, and Japanese maple. This disease is easily diagnosed by observing the creamy orange […]
Common Diseases: Verticillium wilt categories: Common Diseases Common Problems revision date: 2022-11-04 09:32 Vascular discoloration from Verticillium wilt on smoke treePhoto by: R.S. Byther Biology Verticillium wilt is caused by a soilborne fungus. The fungus resides in the soil by means of resting structures and can remain there for many years. When roots of susceptible […]
Common Diseases: Viruses categories: Common Diseases Common Problems revision date: 2022-11-04 09:28 Deformed and mottled leaves from virus infectionPhoto by: R.S. Byther Biology Viruses are submicroscopic in size, which means that they can be seen only with an electron microscope. Viruses are introduced into host plants by various means, including vectors such as insects, fungi, […]
Herbicide Damage: 2,4-D and triclopyr categories: Common Problems Herbicide Damage revision date: 2023-01-09 12:00 2,4-D herbicide damage on tomatoPhoto by: R.S. Byther Biology 2,4-D and triclopyr are hormone-type herbicides used to control annual and perennial broadleaf weeds. These products are translocated throughout the plant in both xylem and phloem. They mimic natural hormones in plants […]
Herbicide Damage: Dicamba categories: Common Problems Herbicide Damage revision date: 2022-11-03 09:37 Twisting and distortion of deodar cedar needles from dicambaPhoto by: R. Maleike Biology Dicamba is a hormone-type herbicide that mimics natural growth regulators produced in plants. It is used for control of broadleaf weeds and is readily absorbed by roots and foliage and […]
Herbicide Damage: Dichlobenil (Casoron) categories: Common Problems Herbicide Damage revision date: 2022-11-02 10:36 Casoron damage causing needle tip chlorosis on pinePhoto by: R. Maleike Biology Dichlobenil is a soil-applied herbicide which inhibits root development and prevents germination and establishment of weed seedlings. While dichlobenil is not translocated in the plant, symptoms resulting from inhibited root […]
Herbicide Damage: Fluazifop categories: Common Problems Herbicide Damage revision date: 2022-11-02 10:23 Necrosis on juniper foliage from fluazifopPhoto by: R. Maleike Biology Fluazifop (fluazifop-p-butyl) is an herbicide used for control of annual and perennial grasses (except for annual bluegrass and fine fescues). It interferes with lipid (fatty acid) synthesis. This herbicide is taken into the […]
Herbicide Damage: Glyphosate and sulfonylureas categories: Common Problems Herbicide Damage revision date: 2022-11-02 09:58 Glyphosate damage causing yellowing of raspberry leavesPhoto by: R.S. Byther Biology Glyphosate is a nonselective herbicide (affects both grasses and broadleaf plants) which interferes with amino acid synthesis. It is translocated throughout the plant via both xylem and phloem. Damage is […]
Herbicide Damage: Horticultural spray oil categories: Common Problems Herbicide Damage revision date: 2022-11-02 09:51 Needle browning and loss on spruce from horticultural oil damagePhoto by: R. Maleike Biology Horticultural spray oils may be applied to plants for control of various diseases, insects and mites. However, if oils are applied when temperatures are below 50 degrees […]
Herbicide Damage: Long-term residual herbicides categories: Common Problems Herbicide Damage revision date: 2022-11-02 09:45 Spiral foliar damage from long-term residual herbicidePhoto by: R. Maleike Biology Uracils, substituted ureas and other long-term residual herbicides are used to obtain total vegetation control usually for long periods of time. These products are persistent in the soil for one […]
Herbicide Damage: Triazines (atrazine, simazine and others) categories: Common Problems Herbicide Damage revision date: 2022-11-02 09:41 Simazine damage on Japanese cherryPhoto by: R.S. Byther Biology Triazines are nonselective herbicides that are used for control of annual and perennial grasses and broadleaf weeds. These products are translocated in plants in the xylem. Older leaves show the […]