What are the key technical points for controlling rust disease in Chaenomeles speciosa (flowering quince)?
Key maintenance points for Chaenomeles speciosa bonsai
(I) Maintenance and managementPlacement: Chaenomeles speciosa bonsai should be placed in a location with ample light and good air circulation. During high temperatures in midsummer, appropriate shading is needed to prevent sunscald and leaf scorch. In winter, it is relatively cold-tolerant; the pot can be buried in soil or placed indoors near a window.
Watering: Normally, just keep the pot soil moist, but be careful to prevent water accumulation in the pot, otherwise root rot easily occurs. During the spring and summer growing season, the pot soil should not be too dry, especially during the flowering period, when sufficient moisture must be maintained in the pot soil.
Fertilizing: In winter, apply sufficient base fertilizer, preferably dry cake fertilizer, decomposed manure, or bone meal. During the growing season, except for the plum rain season, regularly apply dilute liquid fertilizer.
Pruning: Mostly done after flowering. Generally, prune back the branches that have flowered to promote branching and flower bud formation, increasing the number of flowers the following year. At the same time, promptly remove water sprouts, crossing branches, overlapping branches, and other branches that affect the plant's appearance. After leaf drop, during the dormant period, shaping and pruning can be carried out, removing diseased, dead, and aged branches to maintain a certain tree shape.
Repotting: Should be done every 2-3 years, preferably after spring flowering, though autumn is also acceptable. When repotting, combine with root pruning and place base fertilizer at the bottom of the pot.
Pest and disease control: Chaenomeles speciosa often suffers from rust disease attacking the leaves, which can be controlled by spraying 0.5 degree Baumé lime sulfur mixture. Main insect pests include aphids, nettle caterpillars, and red spiders. Control methods are the same as for Malus halliana (Hall crabapple).
(II) Ornamental value
Chaenomeles speciosa blooms in early spring before leafing out. The flowers are red and dazzling, making it the best ornamental period. In autumn, it bears yellow pear-shaped fruits with a fragrant aroma, also quite ornamental. If Chaenomeles speciosa is placed in a greenhouse after autumn for cultivation, it can be brought to bloom earlier, during the Spring Festival.
Occurrence and control of rust disease in ornamental flowers
Rust disease: Caused by fungi of the order Pucciniales, class Teliomycetes, subdivision Basidiomycotina. It mainly harms the leaves of horticultural plants, causing leaf blight and premature leaf drop, seriously affecting plant growth. It is named for the large amount of rust-like material produced on diseased parts.
(I) Rose rust disease
1. Symptoms: All aboveground parts of the rose can be affected, mainly harming leaves and buds. In spring, new buds are covered with bright yellow powdery material; the upper surface of leaves has chlorotic yellow small spots, and the underside has yellow powdery masses that later turn into black powdery masses. Diseased leaves turn yellow, wither, and drop early.
This disease can infect rose buds, leaves, receptacles, tender branches, and other parts. In spring, infected buds turn pale yellow and become swollen, and diseased buds gradually die. After autumn, when axillary buds are infected, a few can grow leaves, but they die after winter. The upper surface of infected leaves shows light yellow irregular lesions, and the underside has black spore masses. Leaves drop prematurely.
2. Pathogen: There are many species of pathogens causing rose rust disease. Nine species are known abroad, and three species are known domestically (fungi). They are Phragmidium mucronatum (Pers.) Schlecht and Phragmidium rosae-rugosae Kasai. Phragmidium rose-rugosae.
3. Disease occurrence patterns
(1) The fungus overwinters as mycelium in buds, which is the main source of infection for the following year.
(2) This fungus is a single-host parasite. Disease resistance also varies among different rose varieties. Bulgarian Red Rose, White Rose, and Soviet perfume roses are relatively resistant.
(3) The optimal temperature for disease development is 24-26 degrees Celsius. Abundant rainfall is the leading factor for disease epidemics.
(4) The fungus overwinters in buds or diseased parts. Plants begin to show disease in late April, with severe occurrence from June to August. High summer temperatures and cold winters result in milder occurrence; warm, rainy, or foggy conditions lead to more severe disease occurrence.
4. Control methods
(1) Promptly remove and destroy diseased buds when found.
(2) When disease occurs, spray 25% triadimefon wettable powder at 1500 times dilution, or spray 75% chlorothalonil at 800 times dilution, or spray 250-300 times dilution of sodium dimethyldithiocarbamate.
(3) Strengthen management, reduce humidity, ensure ventilation and light penetration, or increase potassium and magnesium fertilizer application to improve plant disease resistance.
(4) Promptly clear and burn dead branches and fallen leaves to reduce sources of infection. 2. Generally, spray before the peak disease periods in late June and mid-August, once every 8-10 days, for 2-3 consecutive times. Chemicals include 75% chlorothalonil at 800 times dilution and 50% tecloftalam at 500 times dilution.
(II) Chaenomeles speciosa rust disease
1. Symptoms: Small yellow-green spots first appear on the leaf surface, gradually expanding into orange-yellow or orange-red glossy circular lesions, 6-7 mm in diameter, with a yellow-green halo at the edge. Orange-yellow small granular dots appear on them, later turning black. The diseased tissue becomes thickened and slightly raised toward the leaf underside, growing many yellow-white hair-like structures. Finally, the lesions wither and die, harming leaves and green branches on the alternate host, Sabina chinensis (Chinese juniper).
2. Pathogen: Gymnosporangium haraeanum, Gymnosporangium yamadai.
(1) In China, Gymnosporangium haraeanum is the main species, while Gymnosporangium yamadai has only been found in a few provinces. Both are heteroecious (alternate-host) fungi.
(2) The spermogonial and aecial stages harm Chaenomeles speciosa. The uredinial stage is lacking. The telial stage occurs on alternate hosts such as Sabina chinensis, Sabina chinensis 'Kaizuca', Sabina procumbens, and Sabina squamata. These two rust fungi are extremely similar in morphology.
(3) Spermogonia occur beneath the leaf epidermis, nearly circular or flask-shaped. When mature, they break through the epidermis, with the ostiole exposed and many receptive hyphae extending out. Aecia form on the underside of leaf lesions or on petiole lesions, in the form of slender cylinders. The fungus overwinters as mycelium in diseased tissues of junipers and other hosts.
3. Control methods
(1) Around the planting area of Chaenomeles speciosa, avoid planting alternate hosts such as junipers;
(2) In early spring, before teliospores germinate, spray lime sulfur mixture or sodium pentachlorophenate at 350 times dilution on plants of the genus Sabina to inhibit teliospore germination;
(3) After Chaenomeles speciosa leafs out, spraying 25% triadimefon at 1000-1500 times dilution or 50% carbendazim at 1000 times dilution has good control effects. Bordeaux mixture at equal amounts and 200 times dilution can also be sprayed.
(III) Carnation rust disease
1. Symptoms: Harms leaves and stems. On both sides of infected leaves and on stems, light reddish-brown blister-like lesions form, 1.5-8 mm long. The epidermis of diseased parts ruptures to form cinnamon-colored uredinia, causing leaf and plant withering and death. Later, dark brown telia form.
2. Pathogen: Uromyces dianthi is a heteroecious fungus that overwinters as teliospores. The following spring, teliospores germinate and infect Euphorbia plants, producing spermogonia and aecia. The aeciospores then reinfect Dianthus. Besides harming carnation, this disease also harms Dianthus chinensis and Dianthus barbatus.
3. Control methods
(1) Promptly remove diseased leaves and thoroughly clear diseased plant debris after autumn to eliminate or reduce the primary infection source for the following year.
(2) Maintain good ventilation in the greenhouse and control humidity.
(3) At the early stage of disease, spray protective fungicides such as mancozeb or captan, or use 20% carboxin emulsifiable concentrate at 400 times dilution.
(IV) Peony (herbaceous peony) rust disease
1. Symptoms: After peony (herbaceous peony) leaves are infected, there are no obvious lesions on the upper surface, or there may be circular or irregular brown small spots. On the underside, yellow-brown small blister spots form, rupturing to expose yellow powdery masses, which are uredinia. Later, clustered or scattered dark brown, slender hair-like structures appear on the underside, which are telia. On the alternate host pine trees, it infects branches and trunks, causing spindle-shaped galls.
2. Pathogen
(1) Cronartium flaccidum is a heteroecious fungus.
(2) The rust fungus overwinters as mycelium on pine trees. From April to June, spermogonial and aecial stages are produced on pine trees. After aeciospores mature, they are spread by airflow to peonies, causing infection and damage, and producing uredinia. During the growing season, urediniospores cause repeated infections. Later, telia form, and basidiospores are spread by airflow to infect pine trees.
(3) Generally occurs after the flowering period of tree peonies and herbaceous peonies. Severe damage occurs from July to August. Warm, humid, windy, and rainy conditions favor occurrence. Low-lying flower beds with poor drainage are prone to the disease.
3. Control methods
(1) Strengthen cultivation management. Plants should be grown in higher terrain with good drainage.
(2) In late autumn, remove diseased plants and diseased debris of the herbaceous host.
(3) During the disease period, spray 15% triadimefon at 800 times dilution.
(V) Gladiolus rust disease
1. Symptoms: Orange-red blister spots (uredinia) can appear on both sides of leaves. After 3-6 weeks, small black telia can form around the uredinia.
2. Pathogen: Uromyces transversalis (Thuem.) Wint
3. Disease occurrence patterns: At 16-28°C and 80%-100% relative humidity, urediniospores spread through airflow and cause disease epidemics. No resistant varieties have been found so far.
4. Key control points: Chemicals such as benomyl and mancozeb can be sprayed.
(VI) Chrysanthemum rust disease
1. Symptoms: The following three rust diseases can occur on chrysanthemums.
Black rust: Mostly forms brown blister-like protrusions (uredinia) on the leaf underside. After rupturing, yellow-brown urediniospores are released. Later, dark brown telia form.
White rust: Produces grayish-white to light brown blister spots on the leaf underside. Severely diseased plants have the entire leaf covered with rust spots, causing early leaf withering.
Brown rust: Uredinia mostly form on the upper leaf surface, orange-yellow, remaining under the epidermis for a long time, later opening pores.
2. Pathogen
Black rust: Puccinia chrysanthemi Roze
White rust: Puccinia horiana P. Henn
Brown rust: Phakopsora artemisiae Hirat
3. Disease occurrence patterns: The black rust pathogen overwinters as telia and mycelium on diseased plants. The fungus infects at temperatures between 16-27°C. It generally occurs more in cool regions. The white rust pathogen overwinters in plant buds and infects newly grown seedlings the following spring. Warm and rainy conditions favor occurrence. Disease resistance varies among chrysanthemum varieties.
4. Control methods
(1) Select disease-free plants as propagation material.
(2) The planting site should be high and dry, with good drainage, fertile soil, and good ventilation and light. Plant density should be appropriate, and excessive nitrogen fertilizer should not be applied.
(3) When diseased leaves are found, immediately remove and burn them; after flowering ends, clear diseased plants.
(4) During the disease period, chemicals such as Bordeaux mixture, triadimefon, and carboxin can be sprayed, once every 10-15 days; chemicals such as zineb and chlorothalonil also have good control effects.