Symptom Identification and Control Methods for Ivy Leaf Spot Disease
Symptoms and pathological changes: In the early stage of the disease, very small round dark spots appear on the leaf surface, with oily-looking halos. They later enlarge and turn black. Some become polygonal, and sometimes brown deposits surround the lesions; occasionally canker spots also form on the petioles. Infected leaves generally do not drop off.
The disease overwinters in the diseased tissue. Under warm, humid conditions, the pathogen oozes out of the diseased tissue and spreads via wind and rain or insects, causing primary infection and reinfection. It is more likely to occur where ventilation is poor and light penetration is insufficient.
Control methods: 1. Select disease-free mother plants for propagation. Thoroughly remove diseased leaves to reduce the source of infection. 2. Strengthen management and enhance plant disease resistance: plant at a reasonable density, fertilize scientifically, and take effective measures so that plants grow vigorously and their disease resistance is strengthened. 3. Chemical control: In the early stage of the disease, spray 3000-times-diluted streptomycin sulfate solution or 600-times-diluted 12% green emulsifiable concentrate, or 500-times-diluted 20% Longkejun suspension concentrate. When the rate of diseased leaves reaches 10%-15%, the following chemicals may be chosen: 1500-times-diluted 50% carbendazim wettable powder; or 2000-times-diluted 50% thiophanate-methyl wettable powder; or 400-times-diluted 80% zineb wettable powder; the control effect is even better.
Ivy Anthracnose
Anthracnose
A common disease. It mainly affects leaves, and when damage is severe the leaves turn grayish white; it tends to occur during long spells of autumn rain.
Control methods: Place in a well-ventilated, well-lit spot, and do not water the leaves from overhead. After the disease occurs, spray 500-times-diluted 50% carbendazim wettable powder once every 7 days, for 3-4 consecutive sprays to achieve control. For other methods, see the pest and disease control section for Schefflera octophylla.
Leaf Spot Disease
A common disease. It easily causes leaves to turn yellow and drop, mostly brought on by poor ventilation and a stuffy, humid environment.
Control methods: In the early stage of the disease, remove diseased leaves and burn them in a centralized manner. At the same time, spray 1% Bordeaux mixture once every 7 days, for 4-5 consecutive sprays.
Scale Insects
Scale Insects
A common pest. Affected plants grow poorly and can also be contaminated with sooty mold, causing leaves to turn yellow and drop prematurely.
Control methods: Scrape them off by hand. When the affected area is large, 800-times-diluted 40% omethoate emulsifiable concentrate may also be sprayed. For other methods, see the pest and disease control section for Cycas revoluta.
Phytophthora Blight
(1) Symptom characteristics: The whole leaf or most of the leaf turns brown and rots, or the base of the stem and the base of tender nodes become dark green and water-soaked, soften and constrict, then turn brown to brownish black, and the branches and leaves above the diseased part wither. In some cases, rotten tops or dead heads form directly; sometimes the stem base of cuttings is also affected, producing stem rot. When cuttings carry the pathogen or the soil carries the pathogen, and soil and air humidity are high, the disease occurs easily and spreads rapidly.
(2) Control methods
① Pull out diseased plants promptly when found, and appropriately reduce watering.
② When planting cuttings, be careful to select cuttings from plants free of pest and disease damage, and insert them into a sterilized substrate or one in which Phytophthora blight has never occurred. Planting should not be too dense, and attention should be paid to ventilation and light penetration.
③ Drain promptly during the rainy season to prevent moisture from lingering.
④ In the early stage of the disease, spray or drench with 800-times-diluted 25% metalaxyl wettable powder, or 600-times-diluted 58% metalaxyl mancozeb wettable powder, 600-times-diluted 64% oxadixyl wettable powder, or 600-times-diluted 72% Kelu.
Gray Mold
(1) Symptom characteristics: Water-soaked brown or black lesions form on leaf edges; when severe, the lesions may occupy most of the leaf or the entire leaf, and a gray mold layer forms under humid conditions.
(2) Control methods: Cultivate with new disease-free soil, control watering, and do not apply too much nitrogen fertilizer. Remove diseased leaves promptly and burn them. When the disease occurs, spray 500-times-diluted 75% chlorothalonil. Once every 10 days, for 2-3 consecutive applications.
Purple Protruding Eye Oyster Scale
(1) Damage characteristics: Nymphs and female adults suck sap from branches and leaves. When severe, they cover leaves and branches, causing plants to dry out, turn yellow, and die.
(2) Control methods: In winter, combine with shaping and prune out pest-infested branches and leaves, and burn them in a centralized manner. During the nymph hatching period, spray 1000-times-diluted 50% phoxim or 1500-times-diluted Supracide.
Sunscald
Symptoms: Upper leaves or new leaves turn light gray, gradually wither, and drop.
Cause: A physiological disorder. In summer, ivy that has long been kept in a shaded place and is suddenly placed in bright sunlight is easily burned by intense sunlight.
Control methods: The growing environment should be semi-shaded, with about 50%-70% sunlight. Avoid direct strong sunlight.
Control of Common Pests and Diseases of Ivy
1．AnthracnoseA common disease. It mainly affects leaves, and when damage is severe the leaves turn grayish white; it tends to occur during long spells of autumn rain.
Control methods: Place in a well-ventilated, well-lit spot, and do not water the leaves from overhead. After the disease occurs, spray 500-times-diluted 50% carbendazim wettable powder once every 7 days, for 3-4 consecutive sprays to achieve control. For other methods, see the pest and disease control section for Schefflera octophylla.
2．Leaf Spot DiseaseA common disease. It easily causes leaves to turn yellow and drop, mostly brought on by poor ventilation and a stuffy, humid environment.
Control methods: In the early stage of the disease, remove diseased leaves and burn them in a centralized manner. At the same time, spray 1% Bordeaux mixture once every 7 days, for 4-5 consecutive sprays.
3．Scale InsectsA common pest. Affected plants grow poorly and can also be contaminated with sooty mold, causing leaves to turn yellow and drop prematurely.
Control methods: Scrape them off by hand. When the affected area is large, 800-times-diluted 40% omethoate emulsifiable concentrate may also be sprayed. For other methods, see the pest and disease control section for Cycas revoluta.