Symptoms and control methods of bacterial angular leaf spot of cucumber
Damage caused by bacterial angular leaf spot of cucumber and its control
Bacterial angular leaf spot is one of the major diseases on cucumber, and its occurrence has gradually worsened in recent years. Measures should be taken early for its control.
Cucumber can be affected from the seedling stage to the mature plant stage, mainly damaging the leaves, and occasionally occurring on the fruit and vines. When leaves are infected, small chlorotic spots first appear, then enlarge, and the lesions are restricted by the leaf veins, forming grayish-white or yellowish-brown angular spots. When humidity is high, there is an obvious water-soaked green halo around the lesion on the underside of the leaf, and milky-white water-drop-like bacterial ooze appears on the lesion, leaving a membranous white mark after drying. In the later stage, the lesions dry, crack, and perforate. When the disease is severe, the lesions connect with each other, forming light brown oil-paper-like patches. When the stems and vines are infected, water-soaked small spots first appear, then expand longitudinally into short strips; when humidity is high there is bacterial ooze, and when the disease is severe the vines split longitudinally. When the fruit is infected, water-soaked dark green nearly round sunken spots form initially, then expand into irregular light brown large lesions, with dirty-white bacterial ooze overflowing; when the disease is severe, cracks appear or there is foul-smelling rot. The vascular bundles and fruit flesh of diseased plants turn brown.
1. Agricultural control: (1) Choose disease-tolerant varieties. Varieties such as Jinchun No. 1, Jinzao No. 3, etc. have strong disease resistance and can be selected according to local conditions.
(2) Seed disinfection. Before sowing, soak the seeds in warm water at 55°C for 15 minutes, remove them and put them in cold water to cool down; or soak the seeds in a 150-fold dilution of 40% formalin for 90 minutes, wash them clean with water, then germinate and sow.
(3) Crop rotation. Raise seedlings in disease-free soil, and carry out crop rotation with non-cucurbit crops for more than 2 years.
(4) Strengthen field management. Cultivate with deep ditches and narrow beds, with three ditches matched, to enhance the ability to prevent waterlogging and drain water in the rainy season. Apply sufficient base fertilizer, increase the application of phosphorus and potassium fertilizers, prevent excessive application of nitrogen fertilizer, and enhance plant disease resistance. For open-field cucumber, promote rain-shelter cultivation; for protected cultivation cucumber, before flowering and fruiting, water less, cultivate frequently, and ventilate more to reduce humidity inside the shed and reduce condensation and dripping.
2. Chemical control: To control bacterial angular leaf spot of cucumber, in the early stage of the disease, spray with 14% copper ammonia complex aqueous solution at 300-fold dilution, or 47% Kasugamycin-copper oxychloride wettable powder at 700-fold dilution, or 50% metalaxyl•copper wettable powder at 600-700-fold dilution, or 72% agricultural streptomycin soluble powder at 4000-fold dilution. Spray once every 7-10 days, and decide the number of applications according to the disease condition. Copper preparations should not be applied more than 3 times to avoid phytotoxicity.
Cucumber can be affected from the seedling stage to the mature plant stage, mainly damaging the leaves, and occasionally occurring on the fruit and vines. When leaves are infected, small chlorotic spots first appear, then enlarge, and the lesions are restricted by the leaf veins, forming grayish-white or yellowish-brown angular spots. When humidity is high, there is an obvious water-soaked green halo around the lesion on the underside of the leaf, and milky-white water-drop-like bacterial ooze appears on the lesion, leaving a membranous white mark after drying. In the later stage, the lesions dry, crack, and perforate. When the disease is severe, the lesions connect with each other, forming light brown oil-paper-like patches. When the stems and vines are infected, water-soaked small spots first appear, then expand longitudinally into short strips; when humidity is high there is bacterial ooze, and when the disease is severe the vines split longitudinally. When the fruit is infected, water-soaked dark green nearly round sunken spots form initially, then expand into irregular light brown large lesions, with dirty-white bacterial ooze overflowing; when the disease is severe, cracks appear or there is foul-smelling rot. The vascular bundles and fruit flesh of diseased plants turn brown.
1. Agricultural control: (1) Choose disease-tolerant varieties. Varieties such as Jinchun No. 1, Jinzao No. 3, etc. have strong disease resistance and can be selected according to local conditions.
(2) Seed disinfection. Before sowing, soak the seeds in warm water at 55°C for 15 minutes, remove them and put them in cold water to cool down; or soak the seeds in a 150-fold dilution of 40% formalin for 90 minutes, wash them clean with water, then germinate and sow.
(3) Crop rotation. Raise seedlings in disease-free soil, and carry out crop rotation with non-cucurbit crops for more than 2 years.
(4) Strengthen field management. Cultivate with deep ditches and narrow beds, with three ditches matched, to enhance the ability to prevent waterlogging and drain water in the rainy season. Apply sufficient base fertilizer, increase the application of phosphorus and potassium fertilizers, prevent excessive application of nitrogen fertilizer, and enhance plant disease resistance. For open-field cucumber, promote rain-shelter cultivation; for protected cultivation cucumber, before flowering and fruiting, water less, cultivate frequently, and ventilate more to reduce humidity inside the shed and reduce condensation and dripping.
2. Chemical control: To control bacterial angular leaf spot of cucumber, in the early stage of the disease, spray with 14% copper ammonia complex aqueous solution at 300-fold dilution, or 47% Kasugamycin-copper oxychloride wettable powder at 700-fold dilution, or 50% metalaxyl•copper wettable powder at 600-700-fold dilution, or 72% agricultural streptomycin soluble powder at 4000-fold dilution. Spray once every 7-10 days, and decide the number of applications according to the disease condition. Copper preparations should not be applied more than 3 times to avoid phytotoxicity.