To meet the needs of amateur flower growers, various small, individually packaged pesticides are commonly sold in flower shops. Meanwhile, some research and production units have developed pesticides and fungicides suitable for home use, making it easier to control pests and diseases in home gardening. Several common pests and diseases and their control methods are introduced below:

1. Damping-off disease

Also known as damping-off, it commonly affects seedlings. The pathogen invades from the root and stem base, causing brown lesions and epidermal necrosis. After infection, the entire plant collapses and dies within a short period. Damping-off is caused by a fungus and spreads through the soil. It is more likely to occur when the soil temperature reaches above 20℃ and humidity is high.

Prevention and control methods: Disinfect the soil before sowing. For small quantities, you can steam or stir-fry it. For large quantities, you can irrigate the soil with 4% formalin or 2% ferrous sulfate. Sow the seeds one week later.

2. Powdery mildew

This is one of the most common diseases, affecting the leaves, tender shoots, and even the entire plant of various flowers such as roses, cinerarias, dahlias, and fuchsias. It is more likely to occur when temperatures reach 18–30℃, in humid and poorly ventilated environments. Affected plants first develop yellow spots on the leaves, followed by the growth of white hairs, causing the leaves to curl inwards.

Prevention and control methods:

① Pay attention to ventilation, control humidity, and increase light exposure to prevent powdery mildew.

② Spray with 1% Bordeaux mixture (preparation method attached) before the onset of the disease for prevention.

③ When the disease first appears, remove the diseased leaves and burn them, and isolate the diseased plant for observation.

④ Even after the onset of the disease, you can still spray with 1% Bordeaux mixture to prevent the disease from progressing, or spray with 500-1000 times diluted thiophanate-methyl or carbendazim for treatment.

Appendix: Preparation method of Bordeaux mixture. Dissolve 1 gram of copper sulfate in 50 ml of warm water. Then take 1 gram of quicklime (calcium oxide) (it should be in block form; its powdered form is calcium hydroxide). First, add a small amount of water to dissolve it, then add 50 ml of water and filter out the residue. Next, take a container and pour both solutions into it simultaneously, stirring constantly until it becomes a clear, sky-blue liquid. It is then ready for spraying. When spraying, ensure the undersides and upper surfaces of the leaves, as well as the branches, are all covered.

3. Sooty mold

This disease harms most potted plants, including camellias, citrus, and oleanders. It causes the branches, leaves, and fruits to wither and die. Initially, dark brown mold spots appear on the leaf surface, gradually expanding to form a black, sooty mold layer. Sooty mold often occurs under high humidity conditions, often in conjunction with scale insects and aphids.

Prevention and control methods:

① Ensure ventilation and light penetration to reduce indoor humidity.

② First, control scale insects and aphids to prevent the breeding of sooty mold.

③ Rinse the affected area with clean water.

④ Spray with an equal volume of Bordeaux mixture or dilute with 500-1000 times the amount of carbendazim.

⑤ Add 100 times the amount of copper sulfate or 500 times the amount of potassium permanganate to the spray.

4. Yellowing

Also known as chlorosis. It differs from the three diseases mentioned above; it is not caused by fungal infection but by nutritional imbalance. In North China, acid-loving plants such as camellias, gardenias, and magnolias suffer from chlorosis due to the high alkalinity of the soil and water. This alkalinity causes iron ions in the soil that could be absorbed by plants to become insoluble iron salts, resulting in physiological iron deficiency and hindering photosynthesis, ultimately leading to death.

Prevention and control methods:

① Acidic plants introduced from the south should be cultivated in acidic soil.

② When watering, use rainwater as much as possible in summer. If using tap water, you can add 0.2% alum or ferrous sulfate, or water with 2% to 3% alum water every 7 to 10 days.

③ Regularly irrigate with alum fertilizer solution (see the "Types and Functions of Fertilizers" section for preparation method).

5. Aphids

Aphids are among the most common pests, harming almost all flowers. They often congregate on the tender branches and leaves of plants, sucking nutrients and causing the leaves to curl and turn yellow. Aphid excrement contains honeydew, which becomes a culture medium for some pathogens and often attracts ants, spreading other diseases.

Prevention and control methods:

① Regularly check the branches and leaves of the flowers. If you find a few, you can catch them by hand.

② Spray with 1000-2000 times diluted dimethoate (dimethoate cannot be used on plum blossoms and peach blossoms, as it can easily cause premature leaf drop).

③ Spray with 1500-2000 times diluted dichlorvos with water.

6. Red spider

Small in size and red in color, it can be seen with the naked eye. It grows most vigorously under high temperature conditions and often forms webs or shelters under the leaves. It harms a variety of flowers, and is most prevalent from June to August. Affected leaves turn yellow, and in severe cases, leaves fall off. Over time, the entire plant withers and turns yellow, and may even die.

Prevention and control methods:

① Regularly inspect the flowers, especially the undersides of the leaves, to promptly detect pests. If you only discover pests when the leaves turn yellow, it is too late, and it will be difficult to save the damaged leaves by applying pesticides.

② Increasing humidity and providing proper ventilation can reduce the breeding of spider mites.

③ Spray with 1500-2000 times diluted dimethoate (except for plum blossom and peach blossom varieties), or 1500-2000 times diluted dichlorvos.

7. Nematodes

It is linear, white, and small in size, barely visible to the naked eye. It mainly damages the roots, bulbs, and cuttings of flowers in the soil. Affected plants grow weakly, develop tumors on their roots, and may even rot. Infected cuttings often rot and die.

Prevention and control methods:

① Sterilize the potting soil by steaming or stir-frying it in a pot.

② Pour dimethoate or dichlorvos diluted 1500-2000 times with water into the soil.

8. Whiteflies

Whiteflies, also known as "small white moths," have been rampant in recent years in Shijiazhuang, Beijing, and other places, causing damage to various flowers. Both larvae and adults can suck the leaf tissue of plants. In severe cases, leaves wither and fall off, and their excrement often leads to sooty mold.

Prevention and control methods:

① Spray with dimethoate diluted 1000 times with water (except for plum blossoms and peach blossoms).

② Spray with dichlorvos diluted 1000-1500 times with water. To completely eliminate it, spray once every 7-10 days, for 3-5 consecutive times.

9. Scale insects

Scale insects are diverse in species and damage a variety of flowers, causing slow growth and yellowing of leaves and branches. They excrete sugary sap and waxy substances, clogging leaf stomata and often leading to sooty mold. Scale insects are very difficult to control; in household settings, it is difficult to use highly toxic pesticides, so manual removal is the primary method of control. Scale insects commonly damage the branches, leaves, and fruits of woody flowering plants, so regular inspection is necessary.

10. Earthworms

In agricultural production, earthworms help loosen the soil, but in potted flowers, their frequent activity often damages the root system, which is detrimental to the growth and development of the flowers.

Prevention and control methods:

① Once discovered, they should be captured and killed immediately.

② Water with dimethoate diluted 1500-2000 times with water, 1-2 times a week, for 4-5 consecutive times.

③ Trapping and killing. In summer, cover the surface of the potting soil with horse manure 2-3 cm in the evening. The next morning, quickly pour out the horse manure to kill the earthworms that have burrowed into it. Repeat this several times to kill most of them.

11. Simple methods for controlling pests in potted plants at home

Aphids, spider mites, and whiteflies (small white moths) are several pests that are extremely common in North China, especially in some small and medium-sized towns. Due to the spread of pests from street trees and the influence of suburban agricultural environments, many potted flowers are infested with aphids and spider mites multiple times a year. However, most households lack the pesticides and equipment available for horticultural production. Here are some relatively simple methods for pest control, which can be adopted according to your household's circumstances.

① Take 10 grams of tobacco leaves or tobacco stems, add 1 kilogram of water, boil, and use the clear liquid to spray and kill pests such as aphids and spider mites.

②The entire oleander plant is poisonous. Chop its branches and leaves, boil them in water for half an hour, and use the filtrate to spray and kill aphids and whiteflies. It can also be poured into pots to control root maggots, nematodes and other underground pests.

③ Boil 20 grams of dried chili peppers in 1 kilogram of water. Use the clear liquid to spray and kill pests such as spider mites, aphids, and whiteflies.

④ Cut the leaves of the ailanthus tree into small pieces, add 10 to 15 times the amount of water, boil for 1 hour, and pour the filtrate into a sprayer to kill aphids.

⑤ Take a small stick, tie a small cotton ball to one end, dip it in dichlorvos solution, and insert the other end into the pot of the affected plant. The pests will be killed quickly. If the infestation is severe, cover the flowerpot with a plastic bag. After 4-5 hours, the pests will be fumigated to death.

⑥ If several flowers are simultaneously infested with pests, the affected potted plants can be moved to a toilet or bathroom at night, with the doors and windows closed, and dichlorvos solution dripped onto the ground. The pests will be killed overnight.

⑦ Adding laundry detergent to water at a ratio of 1000 to 1200 can be used to control a variety of pests such as aphids, spider mites, whiteflies, and scale insects.

⑧ If you have a sanitation sprayer at home, generally fill it with about 125 ml of water (i.e., 1/4 jin). When using it to spray insecticide, add 2-3 drops of the solution each time, with a concentration of about 0.1%.

If the prevention and control effect is not good, the concentration of the medicine solution can be increased from 2-3 drops to 4-5 drops.