How to prevent and control common flower diseases and pests? All the practical methods are here

The flowers we cultivate today, whether woody plants or herbaceous flowers, were all introduced from the wild into artificial cultivation. Under long-term careful artificial management, the stress resistance of flower plants gradually declines; from fearing no wind or rain, accustomed to braving the elements, they become “delicate and fragile, unable to withstand the slightest wind.” Therefore, they are extremely susceptible to invasion and damage by diseases and pests. So what are the most common diseases and pests that flowers are prone to? How do we prevent and control them?

I. The most common diseases and their prevention and control methods

1. Late spring cold

This is a non-infectious disease, mainly occurring in areas south of the Yangtze River and parts of the region between the Yangtze and Huai rivers. By the end of March, daytime temperatures have already reached above 20 degrees C, and many people are eager to move their potted ornamental plants from indoors to outdoors for conditioning and care; but at this time, cold air often moves southward, bringing a reversal weather pattern known as “late spring cold,” with early morning minimum temperatures often dropping below 4 degrees C, causing the newly sprouted shoots and tender leaves of some tropical-origin flowers to be “frost-damaged.”

Common ones such as Michelia alba, Aglaia odorata, jasmine, Clivia, Dieffenbachia, Syngonium, fuchsia, Maranta, Anthurium, poinsettia, etc., will have their normal growth in that spring severely affected.

Prevention and control methods: Keep timely track of the weather forecasts from local meteorological stations. When the special “late spring cold” weather occurs, for the small number of potted plants already moved outdoors, they can be moved back into the greenhouse or indoors; if there are many potted plants moved outdoors, they can be gathered together and covered with a double layer of plastic film. In the Yangtze River basin and areas to its north, generally one must wait until after Qingming or after the “last frost period” ends before moving them outdoors. You can lower the temperature by opening doors and windows and adding electric fans, then close the doors and windows at night, so that they have a process of gradually adapting to the outdoor environment.

2. Powdery mildew

It mainly harms ornamental plants such as rose, crape myrtle, Mahonia, Euonymus japonicus, and Muehlenbeckia platyclada. It mainly harms leaves, petioles, pedicels, flower buds and tender shoots. The affected parts are covered with a layer of white powdery substance. In severe cases, the leaves turn yellow, the tender leaves curl, wrinkle and thicken, the flower buds wither and die, deformed flowers appear, and the tender shoots bend and shorten.

Prevention and control methods: Sulfur powder fumigation. In March, use an electric heating fumigator in the greenhouse or shed, place sulfur powder inside, and carry out sealed fumigation, which has a good control effect.

3. Anthracnose

It mainly harms Camellia, Camellia sasanqua, Dracaena fragrans, Hydrangea, Clivia, Rohdea japonica, orchids, Aspidistra, Epiphyllum, rubber tree, Cyclamen, etc. in the greenhouse. It mainly harms leaves, tender shoots and fruits. The lesions are nearly round and grayish brown, and in the later stage the lesions turn grayish white, with obvious concentric rings and whorled (or scattered) small black dots.

Prevention and control methods: Adjust the placement density of potted flowers and the planting spacing and row spacing of field-grown plants to improve ventilation and air permeability. Water appropriately when the potting soil dries out to increase the plant's resistance. In the early stage of the disease, use 80% anthracnose Fumei wettable powder at 500 times dilution, or 50% carbendazim-sulfur suspension at 800 times dilution, spraying alternately, once every 10 days, for 2—3 consecutive times.

4. Gray mold

As the temperature rises, with excessive humidity and poor ventilation, gray mold is still one of the main diseases of indoor flowers. It harms potted flowers such as Gerbera, rubber tree, cineraria, Cyclamen, poinsettia, geranium, Rieger begonia, pothos, Ixora, hibiscus, Anthurium, etc., especially the leaves and petals are severely affected.

Prevention and control methods: After March, strengthen ventilation and light transmission, reduce indoor air humidity, prohibit spraying water on leaf surfaces in the evening, and prevent moisture from remaining on leaf surfaces for a long time.

For plants in the early stage of the disease, around noon, use 65% zineb wettable powder at 500 times dilution, or 50% hymexazol wettable powder at 1000 times dilution, spraying alternately, once every 10 days, for 2—3 consecutive times.

5. Sooty mold

In March, due to poor indoor ventilation and high humidity, piercing-sucking pests such as scale insects, aphids and whiteflies cannot be completely eliminated, and sooty mold still occurs on the leaves, flowers and fruits of plants such as citrus, Aglaia odorata, hibiscus, Michelia alba, Michelia figo, Caryota, ficus, Camellia, Rhapis, azalea, gardenia, Ilex cornuta, and Carmona retusa.

Prevention and control methods: Strengthen indoor ventilation and air permeability, and promptly kill the insect vectors that induce sooty mold, such as aphids, scale insects and whiteflies. If a small number of leaves on individual plants are infected with sooty mold, use a damp cloth dipped in low-concentration laundry detergent water to wipe off the sooty layer. In the early stage of the disease, use 50% thiophanate-methyl suspension at 500 times dilution, or 75% chlorothalonil wettable powder at 500 times dilution to spray the branches and leaves of the affected plants, once every 15 days, for 2—3 consecutive times.

II. The most common pests and their prevention and control methods

1. Mealybugs

Mealybugs are very small, white, hairy parasitic insects that directly invade the plant's vascular system to suck plant sap. They usually hide in or around leaf axils, and can also often be found under the leaves. Moreover, some mealybugs even hide in the plant's roots.

In addition, mealybugs usually lay their eggs in their hiding places (looking like a mass resembling a white cotton area).

Prevention and control methods: A ventilated environment should be maintained; in poorly ventilated environments, plants are prone to mealybugs. Mealybugs are relatively difficult to remove. In the early stage of infection, they can be removed manually, wiped off with alcohol or vinegar, and then rinsed with water. In severe cases, spray “Jiebizhi” insecticide, spraying once a week, and applying the treatment 3 consecutive times can eliminate them.

2. Aleyrodidae

Whiteflies are relatively common pests. They look very much like mini versions of small white moths and can fly. Whiteflies (especially the larvae) usually hide on the undersides of leaves, and the adults also choose to lay eggs on the undersides of leaves.

Prevention and control methods: Try to improve the ventilation of the environment where the plant is located, and avoid plants being too densely packed and the potting soil being too wet. In the early stage of pest occurrence, remove the affected parts and spray the whole plant with diluted acetamiprid. In severe cases, place sticky insect boards beside the plant and shake the branches, which can trap the insects, and then combine this with spraying diluted acetamiprid.

3. Aphids

Aphids usually like to concentrate their attack on the plant's newly grown tender leaves, new buds or flower buds.

Prevention and control methods:

After discovering aphids, you can directly spray Huhuashen insecticide. Adult aphids like yellow, so yellow sticky boards or water trays can be used for trapping and killing. Pay attention to improving the environment, maintaining good ventilation and ensuring proper light.

4. Scale insects

Scale insects are small insects that are flat in appearance, brown, and have a hard shell. They like to cling closely and hide on the stems under the leaves.

Prevention and control methods: In the early stage, scale insects can be removed manually with a toothpick, and “Jiebizhi” should be sprayed once. In severe cases, spray Jiebizhi once a week, for 3 consecutive sprays. Usually, attention should be paid to the ventilation of the plant.

5. Red spider mites

Red spider mites are a relatively common pest. When small spots are found in the band-shaped area under the leaves and between the stems and leaves of the plant, it is very likely that the plant is infected with red spider mites.

Prevention and control methods: In the early stage, the pest-affected parts can be cut off and burned, and chemical control should be used, with two or three chemicals rotated. A suitable recommended chemical is fenbutatin oxide-pyridaben emulsifiable concentrate, which can effectively kill the larvae and adults of red spider mites. You can also cut citrus peel into thin strips or small pieces, add about 10 times the amount of clean water, soak for more than 4 hours, and spray the whole plant, which can effectively prevent and control them.

6. Fungus gnats

Fungus gnats are a very annoying insect. They are extremely small, black, with transparent wings. They like to crawl on the soil, and their eggs and larvae also hide in the soil.

Prevention and control methods: Keeping the potting soil dry can effectively prevent fungus gnats. When fungus gnats are found, you can directly drench the roots with diluted Huhuashen, applying enough to thoroughly soak the soil, and also spray it on the entire plant.

7. Thrips

The body is tiny and slender, appearing white, pale yellow, brown, dark brown or black to the naked eye. They like to inhabit concealed places, such as under the down on the undersides of leaves, inside flower organs, or inside fruit calyxes.

Prevention and control methods: Use 80% dichlorvos emulsion at 1500 times dilution for spraying to kill them (note that the undersides of the leaves must be sprayed).