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How to Solve Plant Problems

No matter how long you’ve been gardening – months, years, or decades, sooner or later, just about every gardener will encounter a plant problem. While many are easily eliminated, there might be occasions when a pest or disease reaches a level where some sort of control measures is warranted.  


What causes plant problems?

Plant problems are caused either by living things, such as pests and diseases, or by non-living actions or conditions. 

Invertebrate pests - insects, spiders and mites, snails, and slugs

Vertebrate pests – birds, mammals, and reptiles
Disease – bacteria, fungi, viruses, and phytoplasmas 

Include: mechanical, physical, environmental, or chemical damage or injury. Read more

Examples include:
Drought stress
Freeze injury 
Nutrient deficiency
Improper cultural practices, such as overwatering

Problems caused by biotic organisms can spread throughout one plant and/or spread to neighboring plants of the same species. Problems caused by abiotic factors can severely damage plants but are not contagious - damage does not spread from plant to plant over time. 

Fireblight (left photo) is a biotic disease, while sunburn damage to the redwood tree (right photo) is abiotic. Credit: UC ANR
Fireblight (left photo) is a biotic disease, while sunburn damage to the redwood tree (right photo) is abiotic. Credit: UC ANR

Additional differences between biotic and abiotic factors and how they affect plants:

Diseases progress over time; they start small and increase in size or severity. Damage often occurs suddenly, such as phytotoxicity (plant injury) from a chemical or weather damage.
Gradual change between damaged and nondamaged plants. Sharp margin of damage between affected and unaffected plants.
Slight gradient of increasing severity at the margin of diseased areas is present. Damage often follows a uniform or repeated pattern on an individual plant or throughout a planting, like damage on a single side of a plant.
Specific damage: Damage occurs to one plant species or cultivar, but rarely to large areas of a mixed planting. Non-specific damage: Damage occurs to not just one plant species but to multiple plant species, including weeds.
Adjacent areas are unaffected.

Something to bear in mind:
When looking for the cause of plant problems, there can be more than one factor affecting a plant’s health. Plant diseases and insects often attack plants that are stressed by an abiotic factor like drought.