Key points of pollution-free control techniques for citrus cultivation
When chemical pesticides are used to control citrus pests and diseases, costs are high and resistance is easily developed. Guiding fruit growers to use the following simple and economical methods gives good results in controlling certain citrus pests and diseases. The specific control methods are as follows.
1. Plant ash to control citrus leafminer: during the shoot-flushing period, start when the new shoot has grown to about 3 cm, and continue until the new shoot matures, sprinkling once every 5-7 days for 5-6 consecutive times, and during the interval, replenish promptly after rain. In the early morning when the dew has not dried, or after rain, or after watering, promptly sprinkle plant ash onto the upper and lower surfaces of the leaves of the new citrus shoots. Throughout the shoot period, the leaves should remain constantly coated with the ash powder until the shoot leaves mature. This method is suitable for greenhouse or open-air citrus nurseries, young citrus orchards, and potted ornamental citrus for controlling citrus leafminer.
2. Lime water to control citrus canker: use 1 part freshly slaked lime powder that has just come out of the kiln and 4 parts clean water to make a lime slurry, filter it, and dilute the filtrate at 5% to control citrus canker. About 20 days before each shoot flush, when the new shoot grows to 5 cm and when the young fruit grows to 3 cm in diameter, spray once every 10-15 days. Spray once during orchard cleanup after harvest. Each spraying should evenly and thoroughly cover the tree body, which can effectively prevent the occurrence of citrus canker and reduce the damage rate to leaves, fruit, and branches. At the same time, spraying 5% lime water during the young fruit stage of citrus can prevent sunscald and improve fruit quality.
3. Clean water to control red spider mites: using mechanical action to wash with clean water can control citrus red spider mites. The method is to use a water pump or spraying machinery and other mechanical means to draw water and channel it to the orchard through a hose. Use wire pliers or another clamp to make the pipe opening fan-shaped with holes (for spraying machinery, use a straight-jet spray gun head), so that when the clean water rushes out it has a certain impact force and evenly washes the tree canopy. This can significantly reduce the population density of red and yellow spider mites, and can also wash off arrowhead scale and other scale insects, as well as aphids, reducing the occurrence of sooty mold; wash dust off leaves and fruit, which helps leaf photosynthesis; during drought it can resist drought, and in hot summer it can lower temperature and increase humidity to prevent fruit sunscald. However, in hot summer, watering must be done before 10 a.m. Note that this method is not suitable for use during the entire flowering period, the period just after new shoots emerge, or the period just after fruit set. It is suitable for use when each shoot has matured and during the fruit growth and expansion period from July to October. The water quality used must be clean and pollution-free.
4. Gasoline to kill longhorn beetles: first use wire to clean out the insect frass from the longhorn beetle boreholes, then use a medical syringe to inject 70# or 90# gasoline directly into the boreholes, and seal the borehole openings tightly with yellow mud slurry so the gasoline does not evaporate, thereby killing the longhorn beetles. The injection amounts of gasoline for young larvae, older larvae, and mature larvae are 2 ml, 4 ml, and 6 ml respectively. Because longhorn beetle boreholes have multiple openings, choose the hole closest to the longhorn beetle for gasoline injection. If insect frass is still found being expelled after gasoline injection control, inject once more. This method has a good effect on controlling longhorn beetles.
5. Soaking liquid of tobacco stems and human urine to control arrowhead scale and aphids: place 0.5 kg of chopped tobacco stems (that is, the stems, petioles, and veins of leaf tobacco and other leftovers that cannot be rolled into cigarettes) in 2.5 kg of human urine and soak for 8 days, then filter and dilute with 25 kg of water for spraying. It can be used for control when citrus arrowhead scale or aphids occur. If 0.1% laundry detergent or 0.4% urea is added during use, the control effect is better.