What are the common pests and diseases of spring flowers?
Spring flowers face quite a few pests and diseases, and the following are the more serious ones in April and May: aphids (greenflies). Hibiscus syriacus (rose of Sharon), Prunus persica 'Duplex' (ornamental peach), Hibiscus rosa-sinensis (Chinese hibiscus), Rosa chinensis (Chinese rose), and Lonicera japonica (Japanese honeysuckle) are all easily harmed by aphids. As temperatures rise, they increase and worsen day by day. They must be detected and controlled early.
Control methods: (1) Spray 50% phosmet, diluted with water 1200-1500 times; (2) for a small number of potted flowers, you can also spray neutral laundry detergent diluted 70-100 times.
Red spider mites. The red spider mites on jasmine, Hibiscus rosa-sinensis (Chinese hibiscus), Asparagus setaceus (asparagus fern), Rosa chinensis (Chinese rose), dahlia and many other flowers mostly begin to cause damage from early April. Control methods: for a small number of potted flowers, you can often rinse the front and back of the leaves with tap water, or spray or dip with boiled and cooled flour-paste water diluted 100-150 times, then rinse once more with clean water after a day or two, which can achieve noticeable results.
Scale insects (flower lice). The scale insects on Magnolia denudata (white magnolia), Rosa chinensis (Chinese rose), Buxus (boxwood), and Pittosporum tobira mostly begin hatching and becoming active from mid-April to mid-to-late May.
Control methods: (1) Before hatching, gently brush the insects off by hand; (2) check frequently. Damping-off disease: when the temperature is in the 20s Celsius, newly sown or last-autumn-sown flowers, saplings, and some flowers prone to root rot are highly susceptible to damping-off disease if soil moisture is high. Control methods: (1) Before sowing, apply 70% quintozene at 3-8 jin per mu to the soil, evenly mixed into the soil; (2) control watering during the tender seedling stage, and do not let the soil become too wet; (3) when diseased seedlings are first found, irrigate with 1% ferrous sulfate, applying 4-8 jin of the solution per sq m each time.
Rust disease. Begonia rust disease easily infects in large amounts after rain in April and May; rose rust disease infects when rose buds are about to open. Control methods: (1) For rose disease, promptly remove and burn the yellow diseased buds that sprout first when sprouting, to eliminate the source of infection; (2) during the initial infection period, spray 15% triadimefon, diluted with water 700-1000 times, with obvious effect.
Powdery mildew. Rose powdery mildew, and the powdery mildew of Impatiens balsamina (garden balsam) and Cotinus coggygria (smoke tree), mostly infect in May and June, and in summer easily cause symptoms such as yellow leaves, withered leaves, and curled tender shoots. Control methods: (1) Pay attention to ventilation and light transmission for the flowers; (2) apply less nitrogen fertilizer and more phosphorus and potassium fertilizer; (3) spray once with 15% triadimefon during the initial infection period, diluted with water 700-1000 times.