How to prevent and control bacterial angular leaf spot in Trichosanthes kirilowii? A detailed explanation of integrated control methods

Trichosanthes kirilowii, also known as Trichosanthes kirilowii Maxim. (Gualou), Yaogua, etc., is a perennial herbaceous vine of the genus Trichosanthes in the Cucurbitaceae family, with the entire plant used for medicinal purposes. The fruit shell is known in traditional Chinese medicine as Gualou, the seed as Gualou Ren, and the root as Tianhuafen. The whole Trichosanthes kirilowii fruit, when used as medicine, can clear heat and dissipate nodules, moisten the lungs and resolve phlegm, nourish the stomach and promote fluid production, etc. Tianhuafen injection is clinically used for mid-term pregnancy, dead fetus, and miscarriage in women, and has a significant inhibitory effect on the growth of cancer cells.

Morphological characteristics of Trichosanthes kirilowii

Climbing vine, up to 10 m long; root tuber cylindrical, thick and fleshy, rich in starch, pale yellowish-brown. Stems relatively thick, much branched, with longitudinal ridges and grooves, covered with white spreading soft hairs. Leaves papery, outline nearly circular, both length and width about 5-20 cm, often 3-5 (-7) shallowly to moderately lobed, rarely deeply lobed or not lobed but only with unequal coarse teeth, lobes rhombic-obovate, oblong, apex obtuse, acute, margin often further shallowly lobed, leaf base cordate, sinus 2-4 cm deep, upper surface dark green, rough, lower surface pale green, both surfaces covered with long soft-hairy bristles along veins, basal palmate veins 5, veinlets reticulate; petiole 3-10 cm long, with longitudinal striations, covered with long soft hairs. Tendrils 3-7 branched, covered with soft hairs.

Flowers dioecious. Male raceme solitary, or paired with a single flower, or solitary on upper branches, raceme 10-20 cm long, robust, with longitudinal ridges and grooves, covered with fine soft hairs, apex with 5-8 flowers, single flower pedicel about 15 cm long, pedicel about 3 mm long, bracteoles obovate or broadly ovate, 1.5-2.5 (-3) cm long, 1-2 cm wide, with coarse teeth in the middle and upper part, base with stalk, covered with short soft hairs; calyx tube tubular, 2-4 cm long, apex enlarged, about 10 mm in diameter, middle and lower part about 5 mm in diameter, covered with short soft hairs, lobes lanceolate, 10-15 mm long, 3-5 mm wide, entire; corolla white, lobes obovate, 20 mm long, 18 mm wide, apex center with 1 green tip, both sides with filamentous fringes, covered with soft hairs; anthers connivent, about 6 mm long, about 4 mm in diameter, filaments free, robust, covered with long soft hairs. Female flowers solitary, pedicel 7.5 cm long, covered with short soft hairs; calyx tube cylindrical, 2.5 cm long, 1.2 cm in diameter, lobes and corolla same as male flowers; ovary elliptical, green, 2 cm long, 1 cm in diameter, style 2 cm long, stigma 3. Fruit stalk robust, 4-11 cm long; fruit elliptical or round, 7-10.5 cm long, yellowish-brown or orange-yellow when mature; seeds ovate-elliptical, flattened, 11-16 mm long, 7-12 mm wide, pale yellowish-brown, with ridge lines near the edge. Flowering period May-August, fruiting period August-October.

Growing environment of Trichosanthes kirilowii

Cultivated in warm and humid climates. Relatively cold-tolerant, not drought-tolerant. It is best to choose sunny, deep soil, loose and fertile sandy loam plots for cultivation. Not suitable for cultivation in low-lying land and saline-alkali land. Often grows in hillside forests, thickets, grasslands, and beside village fields at altitudes of 200-1800 m, and is widely cultivated in its natural distribution area.

Integrated control of bacterial angular leaf spot in Trichosanthes kirilowii

What is bacterial angular leaf spot?

Bacterial angular leaf spot mainly damages leaves and fruit. When leaves are affected, they initially show water-soaked light green spots that later turn light brown, and due to the restriction by leaf veins, they become polygonal. In the later stage, the lesions turn grayish-white and are prone to perforation. When humidity is high, white mucus is produced on the lesions. Lesions on stems and fruit are initially water-soaked, nearly round, later pale gray, with cracks often appearing in the center of the lesions, and bacterial ooze produced when moist. The fruit rots in the later stage and has a foul odor.

Symptoms of bacterial angular leaf spot in Trichosanthes kirilowii:

Occurrence characteristics: Leaves initially show small water-soaked spots, which gradually expand and become polygonal lesions due to the restriction by leaf veins, appearing translucent against light. It seriously affects leaf growth. When female flowers and young fruit are affected, flowers and fruit drop. Pathogenic bacteria are present in large quantities, and high humidity and suitable temperature are the main causes of this disease. It develops rapidly when conditions are suitable.

Integrated control methods for bacterial angular leaf spot in Trichosanthes kirilowii:

1. Agricultural prevention

Variety selection: Use varieties with relatively strong disease resistance such as Jinyan No. 6 and Xiaqing.

Seed treatment: Keep seeds from disease-free areas or disease-free plants to prevent seed-borne bacteria. Seed disinfection should be carried out before germination. Commonly used methods include: hot water seed soaking, soaking in 50°C warm water for 20 minutes; soaking seeds in 200 mg/kg Xinzhimeisu solution or 50% Amobam 500 times solution for 1 hour; or soaking seeds in formalin 150 times solution for 1.5 hours, then washing clean and germinating.

2. Cultivation management

Implement crop rotation with non-cucurbit crops for more than 2 years. Use sterile field soil for seedling raising. Use high-ridge cultivation, lay plastic film, reduce the number of waterings, and lower field humidity. Ventilate protected cultivation in time. Drain in time during the rainy season. Clean the field in time to reduce pathogens in the field.

Strengthen field management. Increase application of phosphorus and potassium fertilizers and prune vines in time. Removing lower leaves, clearing ditches and draining water, and removing weeds in the field and other farming operations can effectively reduce the disease.

3. Chemical control

In the early stage of disease, use 86.2% cuprous oxide (Copper Master) 1000 times solution, 25% Weitaling wettable powder 800, 47% kasugamycin-copper oxide wettable powder 800-1000 times solution, 14% copper ammonia complex aqueous solution 300 times solution, 30% DT fungicide 500 times solution, spray once every 5-7 days, spraying 3-4 times continuously.

During the disease period, choose 57.6% GuanJunQing 1000-1200 times for uniform spraying. For severely affected fields, apply continuously 3-4 times at 7-10 day intervals. Spray evenly and thoroughly, but do not increase the concentration, to prevent phytotoxicity during the flowering period.

4. Biological control

For prevention, use "Xijie" 500 times solution mixed with 30 jin of water for spraying treatment. When the disease is severe, use "Xijie" 50 ml + 10 ml "Garlic Oil" mixed with 30 jin of water for spraying treatment.

5. Precautions

1. Prepare and use immediately; do not mix with strongly acidic or strongly alkaline pesticides. Remember! 2. If it rains within 4 hours after application, re-spray. 3. If there is slight precipitation, it is normal and does not affect the efficacy; just shake well before use.