The leaf spot disease of Forsythia suspensa is caused by the infection of the fungus of semiotics. The pathogen first infects the leaf margin. With the development of the disease, it gradually develops to the middle of the leaf, and the whole plant will die in the later stage of the disease.
The disease began in the middle and late May, and the peak period was in July and August. High temperature and high humidity weather and dense ventilation were conducive to the spread of the disease.
In order to control leaf spot, it is necessary to prune branches frequently, remove redundant branches and over dense branches, and keep plants ventilated and transparent.
In the cultivation of forsythia, we should strengthen the management of water and fertilizer, pay attention to the balance of nutrition, and do not apply partial nitrogen fertilizer.
If Forsythia is found to be suffering from leaf spot disease, 75% chlorothalonil WP 1200 times or 50% carbendazim WP 800 times can be sprayed for prevention and control. Once every 10 days, continuous spraying 3-4 times can effectively control the disease.
The common insect pests of Forsythia suspensa include the broad winged wax cicada, the transparent and sparse wax cicada, the mulberry white scutellus scale, the Ivy round scutellus scale, the round spot curly leaf elephant insect, the dazzling night moth, the pine oak caterpillar, the white whiskered velvet moth.
If Forsythia is attacked by the above pests, different methods should be adopted according to different pests.
Spray 10% imidacloprid wettable particles 2000 times solution or 25% detergent 1000 times solution to kill the cicadas.
Spray 400 times of 95% chlorpyrifos emulsion or 1000 times of 20% suquefenac emulsion to kill Scutellaria sanguinensis at the peak of egg formation.
Spray 3% phenoxycarb emulsifiable solution 3000 times in adult stage of the rotifer.
Spray 20% kangfuduonong solvent 3000 times in larval stage to kill the moth.
Spray 3% high osmotic phenoxycarb emulsifiable concentrate 3000 times in the larval stage of oak caterpillars.
1.2% nicotinic acid 1000 times solution can be sprayed to kill the moth when the damage is serious.
The above methods are only in the early stage of insect damage. If the plants suffer from serious insect damage, they should be treated and destroyed in time to prevent spread.
