Major Symptoms & Possible Causes

Sometimes the cause of a garden problem is easy to identify. Fan‑shaped mounds of soil littering a lawn are obviously the work of a pocket gopher; slime trials leading to plants with large, ragged holes in the leaves can only mean slugs or snails.

A bigger challenge is deducing the source of trouble when many explanations are possible. Leaf yellowing and wilting, for example, may be due to insects, nematodes, diseases, or improper watering. If you can’t find clear evidence of a pest, the best course is to assume that growing conditions are at fault, then to focus on improving them. If you're convinced a pest or disease is the villain, check the rogues’ gallery for a likely candidate— but be sure all the evidence fits before placing blame.

For help in solving problems you can’t identify on your own, consult your Cooperative Extension office or a reputable local nursery.

Symptoms

Possible Causes

Notes

Leaf yellowing

Spider mites
Insects
Nematodes
Root rot diseases
Viral diseases
Over watering
Nutrient deficiencies
Soil chemistry
Old age

Usually pinpoint yellowing
Especially bark borers
Wilting also occurs
Older leaves affected first

Older leaves affect first

Leaf mottling

Viral diseases
Pesticide damage
Natural on some plants



Genetic variegation

Leaf spots

DiseasesInsects
Spider mites
Air pollution
Pesticide damage
Nutrient deficiencies
Soil chemistry

  

Leaf malformations

Sucking pests
Viral diseases
Peach leaf curl
Lack of water
Nutrient deficiencies
Pesticide damage



On peaches and nectarines

Especially from certain weed killers

Holes in leaves

Chewing pests
Birds

 

Leaf drop

Diseases
Bark borers
Improper watering
Improper light
Air pollution
Nitrogen deficiency
Soil chemistry
Natural on some plants








Deciduous plants

Cankers(sunken lesions)

DiseasesInsects
Root stress
Sunburn
Mechanical wounds


Especially borers

From lawn mowers, pruner, and other equipment

Branch dieback

Diseases

Insects

Nematodes
Root stress
Soil chemistry

Especially vascular diseases such as firelight and verticillium wilt
Severe infestation by root or foliar pests or twig girdlers

Root rot

Diseases
Over watering
Root stress
Soil chemistry

Usually fungal

Discolored tissue inside roots and stem

Wilt diseases
Fertilizer damage

  

Root malformations

Nematodes
Diseases
Girdled roots
Natural on some plants


Crown gall, for example
Formed in container
Nitrogen-fixing nodules on legumes

Poor germination

Old Seeds
Uneven irrigation
Incorrect planting depth
Damping-off disease
Soil crusting
Insects
Birds






Root maggots, wireworms

Wilting

Lack of water
Insects
Nematodes
Diseases


Especially borers and root feeders

Root rots and wilt diseases