Causes and Control Methods of Pumpkin Gummy Stem Blight

Pumpkin is a very nutritious and healthy food, and it is also one of the anti-cancer foods. Pumpkin is not only soft and sweet in taste, but also has the effect of lubricating the intestines and promoting bowel movements, making it especially suitable for the elderly and children. Diseases during pumpkin cultivation are relatively few, but they are still affected by gummy stem blight. So why do pumpkins get gummy stem blight? How can the occurrence of this disease be controlled?

1. Why do pumpkins get gummy stem blight?

Pumpkin gummy stem blight, also known as “black rot”, is a common disease of cucurbit crops. This disease mainly damages the stems and vines, leaves, petioles and fruits of the plant, causing the base of the stems and vines to rot, the vines to wither, and the plants to die in patches. In particular, pumpkins cultivated in open fields in autumn are severely affected.

Gummy stem blight mainly occurs in the middle and late stages of pumpkin growth. When the stems and vines are infected, light yellow oil-soaked lesions are mostly produced at the stem nodes of the stem base, gradually turning into grayish-white to light reddish-brown irregular necrotic spots, and reddish-brown gelatinous matter is often secreted from the diseased parts. As the disease develops, the lesions turn dark brown, and densely grown small black particles appear on the surface of the affected parts, which are the pycnidia of the pathogen. In the later stage, the diseased stems shrink or split longitudinally, and even the tissue becomes necrotic, separated, and messy like tangled hemp, while the stems and leaves above the diseased part wither. When the leaves are infected, brown “V”-shaped lesions form at the leaf margins, with a pale yellow outer edge and indistinct concentric rings on them. When the petioles are infected, they first become water-soaked and rotten, and later produce many small black dots, causing the plant to shrink and lodge. When the fruit is damaged, in mild cases nearly circular grayish-white spots form, about 5-10 mm in size, with brown edges; in severe cases, irregular chlorotic or yellow round spots first form, then turn gray to brown or black, and finally the pathogen enters the fruit skin and causes dry rot, while some saprophytic fungi invade at the same time and cause wet rot, damaging the entire fruit. The diseased parts of gummy stem blight produce small black dots, and the vascular bundles do not change color after the diseased stem is cut crosswise; these two points can distinguish it from Fusarium wilt.

Pumpkin gummy stem blight is a fungal disease. The pathogen can overwinter on diseased plant residues and in the soil, and can also overwinter attached to seeds. The pathogen uses asexual conidia as the primary infection source in the field the following year, invading through wounds or stomata of the plant with the help of airflow, rainwater, irrigation water or farming operations, and spreading and diffusing in the field to cause secondary infection.

2. How can the occurrence of pumpkin gummy stem blight be controlled?

First, reduce the humidity inside the shed. When ventilating during the day, pay attention to the timing, and on the premise of ensuring the temperature inside the shed, reduce the humidity inside the shed as much as possible.

Second, during usual farming operations such as pruning branches and removing side shoots, avoid cloudy and rainy weather, handle healthy plants first, and handle diseased plants last, so as to avoid disease spread caused by human operations.

Finally, there is chemical treatment. Because pumpkins often have mixed infections of gummy stem blight and bacterial diseases, when spraying, mix agents for controlling gummy stem blight and bacterial diseases. For example, agents for controlling gummy stem blight include: 25% difenoconazole, 70% thiophanate-methyl, and 50% prochloraz manganese salt; bacterial agents include: zhongshengmycin, thiazolinone, thiodiazole-copper, kasugamycin, etc. It is recommended to use the above agents alternately.

In addition, for areas on the stems where the lesions are relatively severe, thiophanate-methyl or chlorothalonil can be mixed into a paste and applied to the lesions.