What are the common pests and diseases of potted flowers?
Powdery mildew: leaves, petioles, flower stalks or young shoots develop a white powdery coating, and the leaves turn yellow, curl and die; an electric heat fumigator with sulfur powder inside can be used for sealed fumigation. Anthracnose: lesions or small black spots appear, and carbendazim-thiram wettable powder can be sprayed. Scale insects: if there are few, wipe them off with soapy water; if there are many, spray with buprofezin wettable powder.
Disease 1: Late spring cold
Damage
This is a non-infectious disease that mainly occurs in parts of the region south of the Yangtze River and between the Yangtze and Huai rivers. By the end of March daytime temperatures have already reached above 20°C, and many people are eager to move their potted ornamental plants from indoors to the outdoors for conditioning and care; but at this time cold air often moves southward, bringing a reversing "late spring cold" weather pattern, and the lowest temperature in the early morning often drops below 4°C, causing the newly sprouted shoots and tender leaves of some flowers native to the tropics to be "frozen" and damaged.
Common examples such as white orchid, Aglaia odorata, jasmine, clivia, dieffenbachia, Syngonium, fuchsia, maranta, anthurium and poinsettia will have their normal growth that spring seriously affected.
Solution
Keep timely track of the weather forecast from the local meteorological station. 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. The temperature can be lowered by opening doors and windows and adding electric fans, and then closing the doors and windows well at night, so that they have a process of gradually adapting to the outdoor environment.
Disease 2: Powdery mildew
Damage
It mainly harms ornamental plants such as rose, crape myrtle, Mahonia, large-leaf boxwood and Muehlenbeckia. It mainly harms leaves, petioles, flower stalks, flower buds and young shoots. The affected parts are covered with a layer of white powder. In severe cases the leaves turn yellow, the tender leaves curl, shrink and thicken, the flower buds die, deformed flowers appear, and the young shoots bend and shorten.
Solution
Sulfur powder fumigation: in March, use an electric heat fumigator in the greenhouse with sulfur powder inside for sealed fumigation, which has a good control effect.
Disease 3: Anthracnose
Damage
It mainly harms camellia, sasanqua, Dracaena fragrans, hydrangea, clivia, lilyturf, orchid, Aspidistra, Epiphyllum, rubber tree and cyclamen in greenhouses. It mainly harms leaves, young shoots and fruits. The lesions are nearly round and grayish brown, and later the lesions turn grayish white, with obvious concentric rings and whorled (or scattered) small black spots.
Solution
Adjust the planting density of whole pots of flowers and the spacing between plants and rows for ground planting to improve ventilation and air permeability. Water appropriately when the potting soil dries out to increase the resistance of the plants.
In the early stage of the disease, spray alternately with 80% carbendazim-thiram wettable powder at 500 times dilution, or 50% carbendazim-sulfur suspension concentrate at 800 times dilution, once every 10 days, for 2-3 consecutive times.
Disease 4: Gray mold
Damage
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 and anthurium, with leaves and petals being especially severely affected.
Solution
After March, ventilation and light transmission should be strengthened, indoor air humidity should be reduced, and spraying water on leaf surfaces in the evening should be prohibited to prevent moisture from remaining on the leaf surfaces for a long time.
For plants in the early stage of the disease, spray alternately with 65% zineb wettable powder at 500 times dilution, or 50% hymexazol wettable powder at 1000 times dilution around noon, once every 10 days, for 2-3 consecutive times.
Disease 5: Sooty mold
Damage
In March, due to poor indoor ventilation and air permeability 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, white orchid, Michelia figo, fishtail palm, banyan, camellia, Rhapis, azalea, gardenia, Ilex cornuta and Fukien tea.
Solution
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, the sooty layer can be wiped off with a damp cloth dipped in low-concentration soapy water.
In the early stage of the disease, spray the branches and leaves of the infected plants with 50% carbendazim-sulfur suspension concentrate at 500 times dilution, or 75% chlorothalonil wettable powder at 500 times dilution, once every 15 days, for 2-3 consecutive times.
Pest 6: Scale insects
Damage
For potted ornamental plants placed in greenhouses, due to restricted ventilation, insufficient light and relatively high humidity, scale insects are still the main type of pest.
For example, green cottony scale on kumquat, gray mealybug on yew, cotton mealybug on hibiscus, pink hibiscus mealybug on clivia, tortoise wax scale and red wax scale on camellia, horned wax scale on holly, black helmet scale and oystershell scale on cycad, soft scale on rose, white peach scale on Michelia figo and white orchid, pink scale on fingered citron, giant tumor oystershell scale on orchid, white scale on Rhapis, round scale on ivy, coconut round scale on areca palm, arrowhead scale on four-season osmanthus, etc. The species of scale insects on each type of flower differ greatly.
Control methods
For scale insects appearing on a small number of plants at home, use absorbent cotton dipped in 75% alcohol to wipe off the live insect bodies, or dip it in soapy water to wipe off the insect bodies. For smaller scale insects such as arrowhead scale and white peach scale, transparent adhesive tape can be used to stick off the live insect bodies.
Or spray with 25% buprofezin wettable powder at 2000 times dilution, once every 15 days, for 2 consecutive times.
Pest 7: Aphids
Damage
As the temperature rises and the amount of watering increases, aphid damage on indoor ornamental plants also becomes more severe. Aphids pierce and suck the sap of newly sprouted branches and leaves, which affects the normal growth of the plants after the beginning of spring.
Control methods
For aphids on a small number of plants, first sprinkle tobacco powder, plant ash or cinder ash on the insect bodies and leaves, and after about 1-2 hours, rinse clean with clear water, which can kill most of the aphids.
Pest 8: Whiteflies
Damage
The main one is greenhouse whitefly, which harms cineraria, hibiscus, rose, nasturtium and lantern flower; the second is citrus spiny whitefly, which harms kumquat, Fortunella hindsii, bitter orange, fingered citron, rose, white orchid and Aglaia odorata. Their harmfulness should not be underestimated.
Control methods
When the infestation is severe, use 10% imidacloprid wettable powder at 2000 times dilution, or 25% buprofezin wettable powder at 2500 times dilution.