What causes watermelon stems to split open?

Symptom description

The watermelon vines in the greenhouse have already covered the ground. The editor went to the area where the condition was relatively severe, pushed aside the watermelon leaves and saw the splits on the stems, and found that the splitting mostly occurred on the stems between nodes, splitting longitudinally along the direction of the stem. The splits varied in size, some long and some short, but every split had red gum oozing from it.

Some of the severely affected splits showed corky dry rot. According to reports, this condition did not develop gradually, but appeared only recently after one watering. Because of the fear that gummy stem blight had occurred, pesticides were applied promptly for control, but the effect was not very satisfactory.

Analysis

Judging from the situation throughout the greenhouse, the splits on the stems were not caused by infection with gummy stem blight, but by physiological problems. The main reasons were excessive control of watering before hand-pollination of the watermelons and the large day-night temperature difference inside the greenhouse.

Generally, vegetable growers properly control water around the flowering period of watermelons so that the flowers can be pollinated normally, and only water after the fruit has set. During this period, soil moisture is often difficult to control. In addition, the current spring day-night temperature difference is relatively large, with nighttime temperatures below 10°C, while daytime temperatures inside the arched greenhouse can reach above 30°C. In this environment, after sudden watering the stems expand rapidly, just like split fruit, because the cells inside the stems grow faster than the stem epidermis, so a large number of splits appear.

After splitting occurs, the splits are very easily infected by pathogens, so some splits show symptoms of gummy stem blight because of infection with gummy stem blight.

Targeted relief

1. Water reasonably, keep soil moisture stable, and do not let the soil become too dry.

2. Improve the insulation performance of the arched greenhouse, appropriately narrow the day-night temperature difference (the day-night temperature difference should be kept within the range of 12-15°C), and at the same time ensure that there are no sudden severe temperature changes inside the greenhouse.

3. Functional foliar fertilizer can be sprayed to improve the flexibility of leaf and stem cells and avoid splitting caused by drastic changes in the water content within the plant.

4. Protective agents should be sprayed in a timely manner to prevent the splits from being infected by pathogens.