What are the common main pests and diseases of osmanthus?
Potted osmanthus often blooms very little or is slow to bloom. To make osmanthus bloom abundantly with fragrant flowers, you need to master the following main points: variety selection: different varieties of osmanthus do not all bloom at the same time. For example, Yueyuegui, Sijigui and others are early-flowering varieties, with the characteristic of blooming several times a year, some...
Diseases Osmanthus, also known as muxi, is a precious aromatic plant native to China. Xianning is located in southern Hubei and has long been known as the "Home of Osmanthus." In recent years, damage from osmanthus pests and diseases has increased, causing its ornamental value to decline. The common ones include: anthracnose, leaf spot, rot disease, jewel beetle, psyllid, whitefly, scale insect, slug moth, leaf roller, bagworm moth and inchworm, etc. Based on recent years of control practice, their occurrence characteristics and control experience are briefly introduced as follows.
(1) Anthracnose
It easily occurs under high temperature and high humidity conditions, producing nearly round purplish-brown lesions on leaf stems, with small black dots on them, and when the damage is severe, the leaves wither.
Starting from June to July, spray a 500-600 times dilution of zineb for prevention; pay attention to ventilation and light transmission, and water and fertilize reasonably. Remove and destroy diseased leaves promptly when found, and spray a 50% zineb amine 800-1000 times dilution for control. Or thoroughly clear dead branches, fallen leaves and weeds in the field in winter.
(2) Leaf spot
It easily occurs under high temperature and high humidity conditions, with irregular black spots appearing on the leaf surface, bearing black mold, causing the leaves to fall early.
Starting from June to July, spray a 140 times equal-proportion Bordeaux mixture for prevention; after onset, spray a 70% thiophanate 800-1000 times dilution; water and fertilize reasonably; pay attention to ventilation and light transmission; remove dead branches and fallen leaves and burn them in a centralized manner to reduce sources of infection.
(3) Rot disease
It mostly occurs at the root collar. The affected part becomes water-soaked, and after the lesions gradually expand, the plant's growth weakens and may even die. It occurs severely in the rainy summer season.
In early spring, scatter a small amount of sulfur powder around the plant; apply asomate and kerosene agent to severely affected areas.
Pests
(1) Jewel beetle
Adults bite tender leaves into notches, but mainly the larvae bore and feed within the bark layer of branches and trunks. The damaged bark has protruding cracks and exudes oily dotted brown gum. When the damage is severe, the bark bursts open, and the main branch or the entire plant dies.
Manual capture: during the adult emergence period, taking advantage of their death-feigning behavior, shake the branches and trunks before the morning dew dries, and capture them after they fall to the ground. Painting stems and trunks: from the occurrence of adults to the damage period of larvae, apply a 20-30 times dilution of dichlorvos emulsifiable concentrate, omethoate emulsifiable concentrate or monocrotophos emulsifiable concentrate to the stems and trunks, repeating 3-4 times (at intervals of 7-10 d); use 80% dichlorvos emulsifiable concentrate and 10-20 times clay, add an appropriate amount of water to make a paste, and apply it to the damaged parts of branches and trunks, so that when the adults after emergence bite through the bark to emerge, they are poisoned and die.
Adult control: spray the canopy with a 90% trichlorfon 1000 times dilution 2-3 times (at intervals of about 7 d); kill larvae: during the peak hatching period of larvae, scrape off the bark and apply an 80% dichlorvos emulsifiable concentrate 20 times dilution.
(2) Psyllid
Adults and nymphs suck the sap of buds, leaves and tender shoots. Affected leaves develop brown dead 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 a 25% carbaryl wettable powder 200-300 times dilution, or a 50% monocrotophos 2000-3000 times dilution.
(3) Whitefly
Adults and larvae gather on the underside of leaves to suck sap, causing the leaves to turn yellow, wilt, and even die. This insect secretes large amounts of excrement, contaminating the leaves and causing sooty mold.
Seize the young larval stage for spraying, and you may choose 40% Supracide 1500 times dilution, or 2.5% Decis 40 ml, or 40% phosmet 150 ml per mu, etc.
(4) Scale insect
The scale insects damaging osmanthus include red wax scale, chaff scale, cottony cushion scale, etc. 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.
Carry out chemical control during the young nymph stage, and you may choose 40% Supracide 1500 times dilution, or 50% dichlorvos 1000 times dilution, or 40% phosmet 150 ml per mu, etc.
(5) Slug moth
Mainly including yellow slug moth, green slug moth, blue slug moth, flat slug moth, etc. Most overwinter as larvae in cocoons, and the cocoons attach to branches, trunks or in the soil. Adults are strongly phototactic, larvae feed on leaves, and young larvae gather to cause damage, with the heaviest damage in July to August.
Manually remove cocoons, pupae and infested leaves; carry out timely chemical control during the young larval stage, and you may choose 10% cypermethrin 2000 times dilution, or 50% fenitrothion 150 ml per mu, etc.; if conditions permit, use light trapping to kill them.
(6) Leaf roller
There are species such as brown leaf roller, apple small leaf roller and yellow-spotted leaf roller, etc. Their larvae have the habit of rolling leaves and webbing leaves together to feed.
Before the larvae roll the leaves, spray 40% monocrotophos 80 ml per mu, or 50% fenitrothion 200 ml, or 50% fenthion 120 ml per mu, etc.; after the leaf rolls are formed, remove them promptly or quickly crush the insect rolls to death from bottom to top.
(7) Bagworm moth
There are species such as large bagworm moth, tea bagworm moth and white bag bagworm moth, etc. The larvae can spin silk to make cocoons, with various broken twigs and residual leaves attached on the outside, forming bags of various forms. The larvae stay inside the bags, and when moving they extend the head and thorax and carry the bag forward. Mature larvae pupate inside the bag, and the larvae feed on leaves.
During the young larval stage, spray a 95% trichlorfon crystal 1000 times dilution, or a 50% fenitrothion 1000 times dilution, or 50% fenthion 120 ml per mu, etc.
(8) Inchworm
Commonly known as the arching worm. The larvae bite and feed on leaves. Newly hatched larvae are active and can spin silk to hang down, dispersing with the wind to cause damage. Adults are phototactic, and eggs are laid in cracks in the bark of trees or between branches.
Use light trapping to kill adults (before early April, apply limewater to bark cracks of trees, etc., to reduce their egg laying and egg hatching rate). During the young larval stage, spray a 95% trichlorfon crystal 1000 times dilution, or 40% phosmet 150 ml per mu, or 50% fenitrothion 200 ml per mu, etc.
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