At the time of onset, the leaves produce lavender waterlogged irregular lesions with obvious edges and clear boundaries with healthy parts; The others are not clear.

After the lesion turns yellowish brown, it gradually expands, the center turns gray and the edge turns brown.

After several lesions merged, the tissues between the lesions turned yellow and died.

When wet, black powdery mildew layer is produced at the diseased spot.

Seriously damaged leaves will dry up and curl.

2. Pathogenesis regularity Oxalis purpurea leaves grow intensively in the growing season, and the ventilation and light transmission in the lower part are poor. Over-dense planting is prone to leaf spot disease.

The diseased plants and plant residues in the soil are the wintering places for pathogenic bacteria. With the help of airflow and rain, conidia spread, and the high temperature and humid environment is conducive to the spread and spread of diseases. They invade oxalis purpurea from stomata or wounds.

Diseases range from 5

It can happen from the first ten days of the month to the first ten days of September, and it can happen in the greenhouse all year round.

When the temperature is 24-35℃ and the relative humidity is above 90%, the disease is the most serious, especially in rainy season.

Soil continuous cropping is a serious disease.

3. Measures ① Agriculture: Strengthen field management, combine with shaping and pruning of oxalis purpurea, and promptly remove infectious sources such as diseased leaves, residual leaves and dead leaves in the nature reserve.

Avoid continuous cropping as much as possible and take rotation for more than two years.

Strengthen cultivation and maintenance, reasonably fertilize water, pay attention to ventilation and light transmission, and keep the soil humidity moderate.

② Chemistry: 70% thiophanate-methyl 1000 was used at the initial stage of the disease.

Double solution, 50% carbendazim 500

Double solution, spraying oxalis purpurea leaves alternately every 7- 10d.

Spray once, 2-3 times in a row.

Time.

You can also use plant ash 3kg and quicklime powder 1kg.

After mixing and stirring, apply 40-60g per pot, which has obvious effect on leaf spot of oxalis purpurea.

Second, root rot 1. Root rot damages the roots and bulbs of oxalis purpurea.

The damaged plants wilted in the sun during the day and recovered from night to early morning.

The initial symptom is that the leaves of Oxalis purpurea show a similar state of fertilizer deficiency and purple; The roots withered; Less fibrous roots, light yellow brown; The taproot has no obvious symptoms.

With the aggravation of the disease, the plant grows worse and worse, the leaves begin to turn yellow and wither, the fibrous roots rot completely, and the main roots turn dark brown and rot gradually; After extrusion, the root cortex is easy to peel off; Black-brown mold layer and glue can sometimes be seen at the base of bulb.

Finally, the water shortage of plants intensified, and all the leaves of Oxalis purpurea withered and the plants died.

This disease is not easy to be found at an early stage.

2. Pathogenic law: Pathogenic bacteria overwinter in soil and diseased plant residues.

Pathogens invade oxalis purpurea from the root wound, and then produce conidia in the affected area. With the help of rain or irrigation water, it spreads, spreads and reinfects. High temperature and high humidity environment is conducive to its onset.

The occurrence of diseases is closely related to cultivation management besides environmental conditions. The diseases are often more serious because of inadequate soil disinfection, local low-lying water accumulation, immature fertilizer use, underground pests or agricultural operations that damage the roots.

Generally, it is more serious in high temperature season, and it is easy to happen when the soil water content is high.

3.

Measures ① Agriculture: Clean up the cultivation site in time, scientifically fertilize and water, prevent flooding and keep the soil moisture moderate.

Before the cultivation of oxalis purpurea, several chemicals were alternately sprayed and disinfected for many times.

Pentachloronitrobenzene or formalin can be used for disinfection.

Remove and destroy the diseased plants in time.

Root rot fungi are anaerobic bacteria. It is an effective measure to loosen the soil 1 time within 3-5 days after Oxalis purpurea planting to enhance soil permeability.

② Chemistry: Spraying 500-fold solution of 50% thiophanate-methyl and 500-fold solution of 50% carbendazim or root irrigation at the initial stage of the disease.

After onset, the roots can be washed or sprayed with 50% 700 times disinfectant, 50% thiophanate-methyl 1000 times disinfectant, 65% 600-800 times disinfectant and 75% 600 times disinfectant.