Causes of Stem Splitting in Greenhouse Watermelons and How to Treat the Problem Accordingly

It is now spring, and in many farmers' greenhouses the watermelon vines have already covered the ground, but some watermelon leaves have split open, with cuts large and small, long and short, yet every cut has red gum oozing from it. So why exactly do watermelon stems split? How should one “treat the problem accordingly”?

In fact, this situation did not develop gradually, but appeared only recently after one watering. Precisely because of the fear that gummy stem blight had occurred, pesticides were applied in time for control, but the effect was not ideal.

Judging from how it occurred throughout the greenhouse, the cuts on the stems were not caused by infection with gummy stem blight, but by a physiological problem, the main cause being excessive control of watering before fruit setting of the watermelon as well as the large day-night temperature difference inside the greenhouse.

Generally, vegetable growers appropriately control water before and after watermelon flowering so that pollination can proceed 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 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 rapidly expand, 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 cuts are very easily infected by pathogens, so some cuts show symptoms of gummy stem blight because of infection with it.

So how should this be handled?

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

2. Improve the heat preservation performance of the arched greenhouse and appropriately narrow the day-night temperature difference (the day-night temperature difference should be kept within the range of 12-15°C), while ensuring that there are no sudden drastic 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 cuts from being infected by pathogens.