Insect vs. Pathogen Flow Chart
Are there "watermarks" on leaves?
Are there round or angular "lesions" (spots) on leaves?
Is there visible rot at the base of the stem?
Is there a "band" of yellow or green tissue along the larger veins?
Yellow? - yes then viral
Green? yes - nutrient
Is there a patchwork of green and yellow areas over the leaf?
is there a margin between infected vs. non infected areas? - yes- nutritional or genetic
No margin. - viral
Do leaf or stem surfaces have a white, grey, black, or brown "fuzzy" appearance?
Fungal
Burned or scorched leaf edges?
Chemicals absorbed through air or soil
Are there dead or swollen infected areas (cankers) on the stem?
Fungal, bacterial or mechanical injury.
Is any ooze observed?
Bacterial.
Malformation, deformity or abnormal growing of leaves or stems (internodes)?
Insect, fungal, possible viral
Yellowing of leaves?
Systematic (everywhere equally)? - nutrient or insect
Non-systematic (not everywhere equally)? - fungal
Progressive curling and drying of leaves?
Bronzing? - insect
Not bronzing. - fungal, bacterial
Stippling of leaves (tiny white or yellow spots)?
Insect
Nutrient issue
Most likely bacterial, possible fungal
fungal.
fungal.
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