What are the most common pests and diseases of Japanese euonymus (Euonymus japonicus)?

1. Box tree pyralid

The larvae spin silk to bind surrounding leaves and tender twigs into temporary nests, then feed inside them; in severe cases they eat all the leaves, causing the seedlings to die.

Morphological features: the adult has grayish-white body and wings, with purplish-brown broad bands on the costal, outer and inner margins of the forewing; there are two white spots on the purplish-brown costal band, and the scales are glossy with a purplish-red sheen. The larva has a black head, a yellow-green body, and the dorsal line, subdorsal line and upper spiracular line are dark green to dark greenish-black, while the spiracular line is orange-yellow.

Occurrence pattern: in northern regions there are 2 to 3 generations a year; the larvae overwinter in thin cocoons in the bracts, and the adults hide by day and come out at night, with phototaxis.

Control methods: (1) Manual capture and killing: during the adult egg-laying period, combine with pruning of the seedlings to remove egg masses and larval nests and burn them in a centralized manner. (2) During the adult stage, use black light lamps for light trapping and killing. (3) When the larvae cause severe damage, spray 50% fenitrothion emulsion at 1000 times dilution; or 4.5% beta-cypermethrin at 2000 times dilution; or Bt emulsion at 500 times dilution (note: Bt emulsion must never be used together with fungicides, and spraying after 4 p.m. on cloudy days gives better results).

2. Japanese euonymus looper

The larvae gather on leaves to feed; after eating all the leaves they gnaw the bark of tender twigs, causing the whole plant to die. They overwinter as pupae; the adults are not strong fliers and have strong phototaxis.

Morphological features: adult; the female adult has silvery-white wing bases with light gray markings of varying size and irregular arrangement. The forewing has a continuous light gray marking along the outer margin, the median line is not in a row, there is a large spot at the end of the discal cell, and there is a deep yellow, brown and gray mottled patch at the wing base; the abdomen is golden yellow with 9 rows of stripes made up of black spots. The male moth has 7 rows of stripes on the abdomen. The larva is entirely black, with a yellow pronotum bearing 5 nearly square black spots; the spiracular line and ventral line are relatively wide and yellow.

Control methods: (1) Take advantage of the adults' phototaxis and use light trapping and killing during the adult stage. (2) During the larval damage period, spray 50% fenitrothion emulsifiable concentrate at 500 times dilution or 4.5% beta-cypermethrin at 2000 times dilution. (3) Remove egg masses during the egg-laying period. In winter, turn over the soil around the roots to kill overwintering pupae.

3. Japanese wax scale

One generation occurs a year, and the fertilized female adults overwinter on twigs and shoot tips.

Morphological features: female adult: the wax shell is grayish-white or slightly flesh-red, oval. Male adult: the body is dark brown or brown, with the head and thoracic notum darker. Nymph: the wax shell is ovate to elliptical, with the back slightly raised.

Control methods: (1) Quarantine measures: when buying seedlings from other places, plant quarantine procedures must be strictly implemented to prevent artificial spread of the pest. (2) Strengthen garden maintenance and management: through maintenance and management, create environmental conditions unsuitable for scale insect survival. Practice crop rotation, clean the garden in time, and burn fallen leaves, weeds, and diseased and pest-infested branches in a centralized manner to reduce the overwintering pest population base; fertilize reasonably to enhance plant resistance. Prune reasonably to improve ventilation and light penetration, change the living environment of scale insects, weaken their reproductive capacity, and reduce damage. (3) Chemical control: when the pest population density is not high, use a soft brush dipped in a small amount of dichlorvos diluted with water (1:50 to 100 times dilution) to wipe them out. During the peak nymph period, spray washing powder diesel emulsion; 150 to 200 times neem oil emulsion; 1% matrine at 1000 to 2000 times dilution; 2000 to 2500 times Dali Sha, spraying once about every 10 days for 3 consecutive sprays. (4) Protect natural enemies such as parasitic wasps.

4. Mealy plum aphid

Wingless viviparous female aphids and nymphs gather on shoot tips and the undersides of tender leaves to suck sap and cause damage; the damaged leaves often have white waxy secretions, which easily lead to sooty mold, and in severe cases the branches and leaves turn black, affecting plant growth and ornamental value. In the Tangshan area, about 10 generations occur a year.

Control methods: (1) Protect natural enemies such as ladybugs and green lacewings. (2) Chemical control: choose 20% fenvalerate-monocrotophos emulsifiable concentrate at 2000 times dilution or 2000 to 3000 times imidacloprid powder for spraying.

5. Powdery mildew

It damages the leaves of Japanese euonymus; the leaves of affected plants appear shrunken and deformed, affecting growth. Powdery mildew is mostly distributed on the upper surface of Japanese euonymus leaves, rarely on the underside; individual lesions are round, and after the white lesions expand and heal together they become irregular.

Control methods: (1) Prune appropriately to enhance air and light penetration. (2) At the early stage of disease, alternately spray 25% triadimefon at 1300 times dilution, 70% thiophanate-methyl at 700 times dilution, and 50% Tuzet wettable powder at 800 times dilution. If the disease is severe, pruning must be carried out, the diseased leaves removed and burned in a centralized manner, and then fungicides sprayed for control.

6. Japanese euonymus leaf spot

When the damage is severe, it causes the euonymus to shed leaves prematurely, forming bare branches, affecting ornamental value and even causing death.

The disease occurs on new leaves, producing small yellow spots that then expand into irregular large spots; the lesion margins are raised, with a relatively wide brown edge. Outside the raised margin there is an extending yellow halo, and the center is yellow-brown or gray-brown, densely covered with small black dots.