What pesticide is most effective against scale insects, one of the "five small pests", and what natural enemies do they have?
Scale insects, also called mealybugs (scale insects), mainly damage various fruit trees, flowers, succulents and other plants, often gathering in clusters on branches, leaves and fruit, feeding on plant sap, and in severe cases causing plant death. Today the editor will introduce to you what pesticide is most effective against scale insects? What natural enemies do they have?
I. Introduction to scale insects
1. Scale insects are insects of the superfamily Coccoidea in the order Homoptera. Most of their bodies are covered with waxy secretions. They are dioecious: females are wingless, while males have one pair of membranous forewings, with the hindwings transformed into halteres.
2. Morphological characteristics
Female adult: oval, rather flat, 5mm long and about 3mm wide, light pink, with a relatively thick white waxy powder.
Male adult: body purplish brown, about 1mm long, wingspan about 2mm, with one pair of transparent wings.
Egg: oval, light orange-yellow, with a white flocculent egg sac.
Nymph: oval, flat, light yellow.
Pupa: light purple, 1.2mm long.
3. Common scale insects include the Japanese globular scale (peach globular scale), Comstock mealybug, San Jose scale, white peach scale, and giant mealybug. Scale insects damage leaves, twigs and fruit.
4. Once female scale insects and larvae emerge, they live permanently on branches, leaves or fruit, causing leaves to yellow, twigs to wither, and tree vigor to decline, and in severe cases causing plant death. The damage caused by this insect ranks first among the "five small pests" of gardens.
5. Scale insects are widely distributed both in China and abroad, mainly damaging fruit trees such as apple, pear, peach, apricot, plum, Japanese apricot, cherry, citrus, loquat, grape, walnut and persimmon, flowers such as bamboo-section evergreen (Japanese cleyera), ivy, jasmine, crabapple, cherry blossom and Chinese rose, as well as some succulent plants.
6. Scale insects have strong reproductive capacity. High temperature and high humidity in summer are the peak period for pest outbreaks, and late May to early June is when the damage is most severe.
II. What pesticide is most effective against scale insects?
Mid-to-late March is the first key period of the year for clearing scale insects. At this time scale insects enter the recovery activity period after overwintering, have poor pesticide resistance, and are easy to control.
1. Control methods for scale insects on fruit trees
Agricultural control: For orchards with an initial infestation, promptly and thoroughly prune out infested branches or manually brush infested branches. They must be brushed clean, pruned clean, and burned in a centralized manner. Never throw them away carelessly, so as to eradicate the source of the insects.
Chemical control: Because scale insects have a waxy shell, the best pesticides are varieties with strong permeability and systemic action.
① For the Japanese globular scale, it is recommended to use Likeli (40% chlorpyrifos) at 1000 times + Sirun at 3000 times for control.
② For the giant mealybug, before the waxy layer has formed or just as it begins to form, spray Likeli (40% chlorpyrifos) at 1000 times or Longlile (44.5% cypermethrin · chlorpyrifos) at 1000 times.
③ For the Comstock mealybug, choose Likeli (40% chlorpyrifos) at 1500 times or Longlile (44.5% cypermethrin · chlorpyrifos) at 1500 times + Sirun at 3000 times for control.
When using pesticides, it is best to alternate them to avoid pesticide damage. Spray once every 7 to 10 days, for 2 to 3 consecutive sprays. The effect of eliminating nymphs on the tree is relatively good. Be careful to spray onto the scale insects, and evenly wet all branches inside and outside the canopy, until water droplets begin to drip down.
2. Control methods for scale insects on flowers and succulents
Physical control: If the infestation has just occurred, you can directly pierce them to death with a needle, toothpick or tweezers, or directly brush them off with a toothbrush. However, it is best to dip a toothbrush in some soapy water before removing them, and the removed insects should be cleared away promptly.
Biological control: Wipe with alcohol at a concentration of 75% or above. Dip a brush pen in an appropriate amount of alcohol and repeatedly wipe the infested areas. If the leaves are too dense and difficult to wipe, you can directly pour alcohol over the severely affected leaf center area; you can also mix vinegar and water at a 1:1 ratio and soak the plant in it or wipe directly.
Chemical control: Spray with 25% buprofezin wettable powder at 2000 times dilution, once every 15 days, for 2 consecutive times.
After removing the scale insects, remember to change the soil and repot.
III. What natural enemies do scale insects have?
In addition to the elimination methods mentioned above, you can also release their natural enemies to eliminate them. So what natural enemies do scale insects have?
Scale insects have rich natural enemy resources, including predatory and parasitic natural enemies such as square-headed beetles, grey-lipped ladybugs, oligosegmented ladybugs, red ladybugs, Australian ladybugs, black-margined ladybugs, aphid wasps, golden aphid wasps, double-banded giant-horned encyrtid wasps, eulophid wasps, flat-horned encyrtid wasps, and green lacewings.
In addition, when using pesticides for control, try to avoid spraying during the peak period of natural enemies, and choose varieties with high efficiency and low toxicity to reduce harm to natural enemies.
IV. When is the best time to kill scale insects?
The best period to eliminate scale insects —— is from the peak egg hatching period to the nymph stage. At this time the waxy layer of the scale insects has not formed or has just formed, and they are relatively sensitive to pesticides, so less is used and the effect is good.
The above is the relevant introduction to scale insects. For the control of scale insects, everyone must grasp the best time for pesticide application, and it is best to carry out control at the nymph stage. In addition, warm and humid weather is conducive to the occurrence of pests, so you must always pay attention to the condition of the plants.