Late blight (Phytophthora infestans)

Symptoms

Rapidly expanding dark, water-soaked lesions on leaves and stems; white growth may appear underneath in humid weather; fruit develops dark lesions.

How to verify

Compare the photos above with the plant, and check the symptom description against the look-alike records below before acting. The source guide does not carry a separate laboratory verification note for this record.

Next step

Remove and destroy infected plants promptly and never compost them. Avoid overhead irrigation and monitor local alerts. Obtain confirmation quickly; use only a locally registered late-blight program, commonly including mefenoxam, cymoxanil, or mancozeb where permitted, with resistance-management rotation.

Active ingredients

propamocarb HCLfamoxadone + oxathiapiprolinbennthiavalicarb isopropyl + oxathiapiprolindimethomorphdimethomorph + fluazinammandipropamidmandipropamid + cymoxanilcymoxanilmefenoxam + mancozebmefenoxam + chlorothalonilmetalaxyl + mancozebmetalaxyl + potassium phosphitecymoxanil + mancozebcopper hydroxide

Organic active ingredients

copper hydroxidecopper oxychloridecopper sulfate pentahydrate

P. persimilis: allowed / avoid

PERSIMILIS STATUS: RESTRICTED. Mancozeb can damage beneficial mites; use before release and allow at least 7 days before releasing Phytoseiulus persimilis.

Label matters

Active ingredients below are examples, not universal prescriptions. Confirm the diagnosis; use only products registered for tomato and the target problem in your country; and follow the current label for dose, pre-harvest interval, worker protection, compatibility and re-entry. Rotate IRAC/FRAC modes of action. When symptoms are uncertain, obtain a laboratory or extension diagnosis. Integrated pest management (IPM)—sanitation, resistant varieties, irrigation management, monitoring and biological control—should be the first line of defense.

Look-alikes to rule out

Early blight (Alternaria)

Gray mold (Botrytis)

Bacterial speck

Fusarium wilt