Pesticide control methods for pests and diseases of courtyard saplings and flowers

(1) Toxicity and harmful effects of pesticides. Pesticides have side effects on humans and animals, and can sometimes also cause phytotoxicity to plants. For example, dichlorvos and omethoate are toxic to humans and animals, and when used on plants such as plum blossom, winter jasmine, and nandina, they can cause phytotoxicity. Especially in hot, dry weather, or when the pesticide solution concentration is too high, they cause leaf scorching at the edges, discoloration, and defoliation within a few days. So not all pesticides are suitable for all flowers. If some flower species are sensitive to a certain pesticide, another pesticide should be used instead. Therefore, before using a pesticide, the instructions for use must be read carefully.

(2) Pesticide mixing and use. Bordeaux mixture, trichlorfon, dichlorvos, and others must be mixed and used immediately, otherwise they easily lose effectiveness. Most insecticides, such as dichlorvos, omethoate, and derris extract, cannot be mixed with alkaline substances, otherwise they will lose their efficacy. Among pesticides, some can be mixed, some cannot be mixed, and some should be used immediately after mixing. For example, lime sulfur mixture and Bordeaux mixture contain lime components, cannot be mixed with most pesticides, and the interval between spraying them and other pesticides cannot be too short. Bordeaux mixture and lime sulfur mixture also cannot be mixed together, nor used one after the other (there should be an interval of more than half a month).

Whether it is pest damage or disease, if only one or two pesticides are used alone over the long term, resistance and pesticide tolerance will develop and they will lose effectiveness, so several insecticides or fungicides should be selected for rotation.

(3) Pesticide dosage. The pesticide dosage must be accurate, the pesticide must be selected precisely according to the disease or pest, and the concentration must not be too high or too low. When spraying, it must also be sprayed on the main diseased areas; insecticides should be sprayed where pests are concentrated and hidden, so that the control effect is better.

(4) Timing of application. Weather, formulation, and the patterns of pests and diseases should be considered to determine the spraying time, so as to improve efficacy. For example, contact and stomach-poison pesticides should preferably be sprayed on sunny days, with no rain for 2 days, to ensure efficacy. Emulsifiable concentrate pesticides can only be applied after the dew has dried, and there should be no rain within I day after spraying to ensure an effective concentration. Powder formulations sprayed before the dew has dried easily adhere to branches and leaves, and there should be no rain within 2 days after spraying. Pesticides for controlling night-active pests have the best effect when sprayed in the evening. Highly toxic, volatile, and easily decomposed pesticides should be avoided during midday high temperatures or windy weather, so as to prevent the pesticide from rapidly volatilizing and losing effectiveness.