How to prevent and control Alternaria leaf spot on cockscomb? Practical methods shared
Affected plant: cockscomb (Celosia cristata L.).
Distribution and damage: This disease occurs mainly in Zhejiang, Yunnan and other places, and causes severe damage.
Symptoms: On the upper surface of leaves there are round, oval, irregular dark brown spots. Early-stage spots are small round dots with a white center and a brown outer ring, 1 mm in diameter; later-stage spots measure ((5-18 mm) x (5-8 mm)), and the edges can join to form large spots, with the edges slightly raised, somewhat ring-like, bearing a gray or black mold layer.
Pathogen: The pathogen is Alternaria celosiae. Conidiophores are straight or branched, bent, light brown, with 0-3 septa. Conidia are grenade-shaped, club-shaped, pear-shaped, light brown or brown, generally with 1-6 transverse septa, 0-2 longitudinal septa, with a longer and paler beak.
Disease pattern: The pathogen overwinters as mycelium in diseased residues. In early summer of the following year it produces conidia, which are spread by wind and rain to cause disease, with reinfection. Disease is likely when the temperature is relatively high and the humidity is relatively high. Lower leaves are more severely affected, and seeds can carry the fungus with spores attached.
Control methods: In the later stage of plant growth, promptly remove diseased plants and diseased residues, and burn them in a centralized manner or bury them deeply. When grown in pots, it is advisable to replace with new soil. In the early stage of disease, remove diseased leaves, apply more potassium fertilizer, apply less nitrogen fertilizer, pay attention to drainage, and do not let the potting soil be too moist. Before sowing, dress seeds with 500% thiram wettable powder. In the early stage of disease, spray 50% iprodione wettable powder at 1500 times dilution, or 75% chlorothalonil wettable powder at 600 times dilution, or 40% difenoconazole wettable powder at 300-400 times dilution.
Damage symptoms on cockscomb
Control methods for Alternaria leaf spot on cockscomb
I. Damage symptoms
On the leaf surface, dark brown round to oval or irregular spots appear, 1—10 mm in size, with slightly raised edges, grayish brown in the middle and somewhat ring-like, with gray-black mold-like growth. At first they are small round dots with a white center and a brown outer ring, 1 mm in size, and later merge into large spots of 5—18 X 5—8 (mm).
II. Morphological characteristics of the pathogen
Alternaria celosiae Tassi, belonging to the imperfect fungi; conidia are club-shaped to pear-shaped, brown, with transverse and longitudinal septa, and the stalk and beak are paler and longer, 17.5—75 X 6.3—10.5 (um) in size.
III. Disease characteristics
It overwinters as mycelium and conidia on diseased residues, or as Alternaria celosiae conidia outside diseased tissues, or attached to the seed surface, becoming the primary infection source the following year. At room temperature, conidia attached to the seed surface can survive for more than 1 year, while mycelium inside the seeds can survive for more than a year and a half; mycelium on diseased residues can survive for 2 years when stored indoors, and for more than 1 year on the soil surface or in moist soil. During the growing period, conidia produced on diseased parts are spread by wind and rain, and germinating conidia can directly invade leaves; under suitable conditions symptoms appear in 3 days, and conidia are quickly formed for reinfection. Seed-borne infection is an important route of long-distance spread.
IV. Epidemic dynamics
The occurrence of this disease is mainly closely related to temperature and humidity during the growth period. Disease appears when the temperature is 14—36°C and the relative humidity is above 80%. It is prone to occur when there are many rainy days, large rainfall, and relative humidity above 90%; clear days and long sunshine hours have a certain inhibitory effect on the disease. In production, continuous cropping, excessive nitrogen fertilizer, poor drainage, and retention of moisture lead to severe disease.
V. Control methods
(1) Select disease-free seeds.
(2) Rotate crops and change stubble.
(3) Apply Baode biological fertilizer or compost fermented with enzyme bacteria or fully decomposed organic fertilizer to improve disease resistance. Strictly prevent flooding irrigation.
(4) For cockscomb maintained in greenhouses, use the dust method or smoke method in the early stage of disease. ① Dust method: in the evening, dust 5% chlorothalonil dust at 1 kg per 667 sq m. ② Smoke method: in the evening, light 45% chlorothalonil smoke agent at 200—250 g per 667 sq m, once every 7-9 days, used continuously or alternately according to the condition.
(5) For cockscomb cultivated in the open field, in the early stage of disease spray 75% Daconil wettable powder at 600 times dilution or 50% iprodione wettable powder at 1000 times dilution, 80% Dacotech wettable powder at 600 times dilution, 80% Pencozeb wettable powder at 600 times dilution. Start applying the pesticide before disease onset, spray 60 L of the prepared solution per 667 sq m, once every 7—10 days, for 3-4 consecutive treatments. If rain occurs 4 hours after spraying, respray; timely spraying after rain in production can reduce damage.
Control techniques for Alternaria leaf spot on cockscomb
Cockscomb is a common indoor ornamental flower. Its flowers are as beautiful and striking as a rooster's comb. Cockscomb gets its name because its inflorescence is red and flat, shaped like a rooster's comb, and enjoys the reputation of "the bird among flowers." Cockscomb is one of the famous herbaceous flowers grown outdoors in gardens. The inflorescence is terminal and conspicuous, with diverse shapes and colors, bright and lively, and has high ornamental value. It is also an important flowerbed flower. Cockscomb is a fairly easy plant to grow, but during cultivation, Alternaria leaf spot often occurs, which distresses flower lovers. Below, the editor will explain its control methods.
1. Symptoms: On the upper surface of leaves there are round, oval, irregular dark brown spots. Early-stage spots are small round dots with a white center and a brown outer ring, 1 mm in diameter; later-stage spots measure ((5-18 mm) X (5-8 mm)), and the edges can join to form large spots, with the edges slightly raised, somewhat ring-like, bearing a gray or black mold layer.
2. Pathogen: The pathogen is Alternaria celosiae. Conidiophores are straight or branched, bent, light brown, with 0-3 septa. Conidia are grenade-shaped, club-shaped, pear-shaped, light brown or brown, generally with 1-6 transverse septa, 0-2 longitudinal septa, with a longer and paler beak.
3. Disease pattern: The pathogen overwinters as mycelium in diseased residues. In early summer of the following year it produces conidia, which are spread by wind and rain to cause disease, with reinfection. Disease is likely when the temperature is relatively high and the humidity is relatively high. Lower leaves are more severely affected, and seeds can carry the fungus with spores attached.
4. Control methods: In the later stage of plant growth, promptly remove diseased plants and diseased residues, and burn them in a centralized manner or bury them deeply. When grown in pots, it is advisable to replace with new soil. In the early stage of disease, remove diseased leaves, apply more potassium fertilizer, apply less nitrogen fertilizer, pay attention to drainage, and do not let the potting soil be too moist. Before sowing, dress seeds with 500% thiram wettable powder. In the early stage of disease, spray 50% iprodione wettable powder at 1500 times dilution, or 75% chlorothalonil wettable powder at 600 times dilution, or 40% difenoconazole wettable powder at 300-400 times dilution.