When Does Hollyhock Bloom? Key Points of Common Pest and Disease Control Methods
Hollyhock is also called yizhanghong, rongkui, and other names. It is cultivated all over the world, and its flowers come in many colors with a relatively unique flower shape, giving it a certain ornamental value. The flowers and leaves of hollyhock are both edible and can be used as medicine, with effects such as clearing heat and promoting diuresis. So when does hollyhock generally bloom? What are the key points of common pest and disease control methods?
I. When does hollyhock generally bloom?
The flowering period of hollyhock is from February to August. If planted in the first year, it can bloom in the second year and can continue blooming for many years. Hollyhock sown in September will keep growing and developing the following year. If the timing of maturity has missed the flowering period, then the flowers can only be seen in the third year. However, if the method of division or cuttings is used, then flowers can be seen in the same year, as its growth is very fast.
II. What are the key points of common pest and disease control methods for hollyhock?
Common diseases of hollyhock include hollyhock white spot disease and hollyhock brown spot disease.
1. Hollyhock white spot disease
Symptoms: White spot disease mainly harms the leaves of hollyhock. In the early stage of the disease, small brown spots appear on the leaf surface. As the disease develops, the spots gradually expand into round, oval, or irregular shapes. The center of the spots is grayish white, and the outer edge is reddish brown. In humid environments, a grayish brown mold layer can form on the spots.
Disease pattern: White spot disease is caused by infection by the fungus Cercospora althaeina, a deuteromycete. The pathogen overwinters in the soil and on diseased residues as mycelium and conidia, and the conidia spread through wind and rain or watering. The disease begins in mid-to-late June, with July and August being the peak periods of incidence. It is especially likely to occur during periods of high temperature and high humidity, can cause repeated infection, and can form 2—3 peak periods of incidence within one year.
Control methods: Diseased leaves can be removed promptly, and attention should be paid to the density of branches and stems so that the plants remain well ventilated and exposed to light; increase the application of phosphorus and potassium fertilizers, and apply little or no nitrogen fertilizer; in the early stage of the disease, spray 75% chlorothalonil wettable powder at 800 times dilution, or 50% carbendazim wettable powder at 500 times dilution, or 70% thiophanate-methyl wettable powder at 1200 times dilution for control, once every 10 days. Spraying continuously 3—4 times can effectively control the disease.
2. Red spider mite
During the growth period, red spider mites may cause damage.
Control methods: When the infestation is severe, spray evenly with 1.8% abamectin emulsifiable concentrate at 7000 to 9000 times dilution for control; or use 15% pyridaben emulsifiable concentrate at 2500 to 3000 times dilution, both of which have relatively good control effects. Avoid using dichlorvos to kill mites, as dichlorvos has the effect of stimulating mite proliferation. Do not use pyrethroid pesticides, as they are basically ineffective for mite control.
3. Borers
Sometimes the cotton leaf roller also harms hollyhock leaves.
Control methods: When it occurs, spray Bt wettable powder with a content of 16000 IU/mg at 500 to 700 times dilution, or 25% diflubenzuron suspension concentrate at 1500 to 2000 times dilution, or 20% miman suspension concentrate at 1500 to 2000 times dilution, etc.