Occurrence Patterns and Control Methods of Major Pests and Diseases of Osmanthus

Osmanthus, also known as sweet olive (Osmanthus fragrans), is a precious aromatic plant native to China. In recent years, pests and diseases of osmanthus have shown an upward trend. Common pests and diseases include: anthracnose, leaf spot, rot disease, jewel beetles, psyllids, whiteflies, scale insects, slug moths, leaf-roller moths, bagworms and geometer moths. Based on control practices in recent years, their occurrence characteristics and control methods are briefly described below.

I. Occurrence Characteristics and Control Methods of Major Diseases

1. Anthracnose: It occurs easily under high temperature and high humidity conditions, producing nearly circular purplish-brown lesions on leaves and stems, with small black dots on them, and causing leaf blight when the damage is severe. Starting from June to July, spray 500-600 times diluted zineb solution for prevention. At the same time, pay attention to ventilation and light penetration of the tree, and rational watering and fertilization. Remove and destroy diseased leaves promptly when found, and spray 50% amobam 800-1000 times diluted solution for control. In winter, thoroughly clear dead branches, fallen leaves and weeds from the field.

2. Leaf spot: It occurs easily under high temperature and high humidity conditions, with irregular black spots appearing on the leaf surface, and black mold growing on the spots, causing premature leaf drop. Starting from June to July, spray 140 times diluted equal-amount Bordeaux mixture for prevention. After onset, spray 70% thiophanate 800-1000 times diluted solution for control; water and fertilize rationally; pay attention to ventilation and light penetration; clear dead branches and fallen leaves and burn them in a centralized manner to reduce infection sources.

3. Rot disease: It mostly occurs at the root collar, with the affected part appearing water-soaked. After the lesions gradually expand, they cause the plant to weaken and even die. In early spring, spread a small amount of sulfur powder around the plant; apply asomate plus kerosene agent to severely affected areas.

II. Occurrence Characteristics and Control Methods of Major Insect Pests

1. Jewel beetle: Adults bite and feed on young leaves, causing notches, but the main damage is caused by larvae boring and feeding within the bark and cambium of branches and trunks. The damaged bark has protruding cracks and exudes oily dotted brown gum. When the damage is severe, the bark splits open, and the main branches or the entire plant die.

A. Manual capture and killing: During the adult emergence period, taking advantage of their death-feigning behavior, shake the branches and trunks in the early morning before the dew dries, and capture and kill them after they fall to the ground.

B. Applying pesticides to branches and trunks: From adult occurrence to larval damage period, brush 20-30 times diluted dichlorvos emulsion, omethoate emulsion or monocrotophos emulsion on the branches and trunks, repeating 3-4 times (with each interval of 7-10 days). Use 80% dichlorvos emulsion plus 10-20 times clay, add an appropriate amount of water to make a paste, and brush it on the damaged parts of the branches and trunks, so that adults after emergence are poisoned to death when they bite through the bark and emerge from the holes.

C. Spraying for control: 90% trichlorfon 1000 times diluted solution can be used to spray the canopy 2-3 times (with each interval of about 7 days) to control adults.

D. Poisoning larvae: During the peak hatching period of larvae, scrape off the bark and apply 80% dichlorvos emulsion 20 times diluted solution.

2. Psyllid: Adults and nymphs suck sap from buds, leaves and tender shoots. Affected leaves develop brown necrotic spots, and in severe cases the entire leaf turns brown, causing early defoliation. Nymphs secrete large amounts of honeydew on the leaves, inducing sooty mold. During the peak occurrence period of nymphs, spray 25% carbaryl wettable powder 200-300 times diluted solution, or 50% monocrotophos 2000-3000 times diluted solution.

3. Whitefly: Adults and larvae gather on the underside of leaves to suck sap, causing leaves to turn yellow, wilt, and even die. This insect secretes large amounts of excrement, contaminating the leaves and potentially causing sooty mold. Seize the young larval stage for spraying, and 40% methidathion 1500 times diluted solution can be selected for spraying and killing.

4. Scale insects: Scale insects damaging osmanthus include red wax scale, Chaff scale, cottony cushion scale, and others. The nymphs and adults of scale insects insert their mouthparts into the tissues of the host plant to suck sap, causing branches and leaves to wither and die. At the same time, most scale insects can secrete honeydew, inducing sooty mold, and the damage is severe. Grasp the young nymph stage for chemical control. 40% methidathion 1500 times diluted solution, or 50% dichlorvos 1000 times diluted solution, or 40% phosmet 150 mL per mu, etc., can be selected.

5. Slug moth: Mainly including yellow slug moth, green slug moth, blue slug moth, flat slug moth, and others. Most overwinter as larvae in cocoons, and the cocoons attach to branches, trunks or in the soil. Adults have strong phototaxis. Larvae feed on leaves, and young larvae gather to cause damage, being most severe in July to August. Manually remove cocoons, pupae and infested leaves. Carry out chemical control promptly during the young larval stage. 10% cypermethrin 2000 times diluted solution or 50% fenitrothion 150 mL per mu can be selected for control. Where conditions permit, light trapping can also be carried out.

6. Leaf-roller moth: There are species such as brown leaf-roller moth, apple small leaf-roller moth and yellow-spotted leaf-roller moth. Their larvae have the habit of rolling and webbing leaves for feeding. Before the larvae roll the leaves, spray 40% monocrotophos 80 mL per mu, or 50% fenitrothion 200 mL per mu, or 50% fenthion 120 mL per mu, etc. After the leaf rolls are formed, remove them promptly or quickly pinch the insect rolls to death from bottom to top.

7. Bagworm: There are species such as large bagworm, tea bagworm and white sac bagworm. Larvae can spin silk to make cocoons, with various broken branches and residual leaves attached on them, forming bags of various forms. The larvae remain inside the bags, extending their head and thorax when moving, and carrying the bags forward. Mature larvae pupate inside the bags, and the larvae feed on leaves. During the young larval stage, spray 95% trichlorfon crystal 1000 times diluted solution, or 50% fenitrothion 1000 times diluted solution, or 50% fenthion 120 mL per mu, etc.

8. Geometer moth: Commonly known as the inchworm, its larvae bite and feed on leaves. Newly hatched larvae are active and can spin silk and hang down, dispersing with the wind to cause damage. Adults have phototaxis, and eggs are laid in cracks in the bark of trees or between branches.

Use light trapping to kill adults. Before early April, brush lime water on bark cracks and other parts of trees to reduce egg laying and egg hatching rates. During the young larval stage, spray 95% trichlorfon crystal 1000 times diluted solution, or 40% phosmet 150 mL per mu, or 50% fenitrothion 200 mL per mu, etc.