Causes, treatment methods, and medication for tomato black stem disease

Does black stem on your tomatoes give you a massive headache? Don't panic! Today I'll walk you through finding the cause and treating it accordingly!

1. Black stem at the base of the stem: check the roots and vascular bundle first
 
Stem base rot: Rhizoctonia solani is the main culprit! It strikes most often in the early stages after transplanting, forming brown sunken lesions that ring the stem base, and later producing pale brown, cobweb-like mold. Although the roots stay intact, the plant gradually wilts and dies

Solution: drench the roots with hymexazol+metalaxyl, and avoid planting too deep at transplanting.

Phytophthora root rot: Phytophthora parasitica is causing trouble! The stem base rots to a dark brown, and when cut open the vascular tissue shows browning. The biggest difference from stem base rot is whether the vascular bundle has discolored, so be sure to identify it correctly!

Solution: in the early stages of disease, drench with refined metalaxyl+fludioxonil, and control watering to avoid waterlogging.

2. Black stem on the middle and upper parts of the stem: look at the symptoms and where the disease occurs
 
Late blight: Phytophthora causes water-soaked dark brown spots on the stem that expand around the stem into sunken cloud-like rings, and in high humidity white mold also appears.

Solution: spray with dimethomorph+azoxystrobin, focusing on the stems and the undersides of the leaves.

Stem blight: Alternaria causes oval brown canker spots that spread into the vascular bundle"march in", eventually causing the plant to wither.

Solution: after disease onset, spray with difenoconazole+prochloraz, and remove diseased leaves to reduce spread.

Stripe virus disease: the virus specifically attacks the stem near the growing point, causing dark brown spots on the epidermis that do not penetrate into the vascular bundle; it can only be tackled with a virus inhibitor.

Solution: promptly spray with moroxydine hydrochloride+zinc fertilizer, and at the same time control aphids (the main transmitters of the virus).

3. Key points for daily prevention:

1. Before transplanting, mix carbendazim into the soil to disinfect it, and avoid continuous cropping.

2.Ventilate promptly after watering to lower the humidity inside the greenhouse (high humidity is a breeding ground for disease).

3.If scattered diseased plants are found, pull them out immediately and spray the surrounding plants as a preventive measure.