Technical Guide for the Prevention and Control of Pests and Diseases of the Chinese Medicinal Herb Chuan Phellodendron (Phellodendron amurense)

Diseases

Rust disease Damages leaves. Occurs in mid-May, with severe damage from June to July. The pathogen is a basidiomycete fungus. It can be sprayed with 20% carboxin emulsifiable concentrate at 200-400 times dilution, once every 10-15 days, 2-3 times per year, with good control results.

Damping-off disease Damages seedlings. Seeds rot before emergence; after emergence the stem base rots, develops in a ring upward, constricts and dies, yet remains upright. It belongs to the Deuteromycotina. Caused by over-dense planting, excessive nitrogen fertilizer, and excessive soil moisture and heavy clay soil. Control: seed dressing with thiram and carbendazim; at the early stage of seedling disease, control with validamycin and carbendazim.

Angular leaf spot Damages leaves. The pathogen belongs to the Deuteromycotina. It has a great impact on young trees. In Sichuan it occurs in July, with peak occurrence from August to October. At this time there is much rain and the disease is severe. Control: strengthen management, clear away diseased and dead leaves, spray with thiophanate-methyl, carbendazim and chlorothalonil once every 15 days. This disease occurs mixed with rust disease, so it can be controlled together with rust disease.

Brown spot Damages leaves. The pathogen belongs to the Deuteromycotina. In Sichuan it occurs in July, with peak occurrence from August to September. At this time there is much rain and the disease is severe. Control: strengthen management, clear away diseased and dead leaves, spray with thiophanate-methyl, carbendazim and chlorothalonil once every 15 days. This disease occurs mixed with rust disease, so it can be controlled together with rust disease.

White mold Damages leaves. The pathogen belongs to the Deuteromycotina. It occurs sporadically and has a slight impact. It occurs from July to September, with high incidence in August. Generally no special control is needed; if control is required, refer to angular leaf spot.

Felt disease Damages the trunk and large branches. The pathogen belongs to the Basidiomycotina. It occurs sporadically and the damage is not serious. It is mostly seen in weak trees and shaded forest areas. Control: scrape off, prune and destroy; control with Bordeaux mixture and carbendazim.

Sooty mold Damages leaves. The pathogen belongs to the Ascomycotina and is an epiphytic fungus. It occurs commonly and lives heterotrophically on the secretions of psyllids and aphids. Control methods: do a good job of controlling psyllids and aphids; control can be carried out with thiophanate-methyl and lime sulfur.

Powdery mildew Damages leaves. The pathogen belongs to the Deuteromycotina. The disease occurs sporadically and the damage is very slight, so no control may be needed. In nurseries, control with triadimefon and lime sulfur.

Ring rot Damages leaves. The pathogen belongs to the Deuteromycotina. The disease occurs commonly and sporadically. The pathogen overwinters in residual plant debris and spreads by rain. It occurs from June to August and is severe from August to October. Control methods: eliminate residual debris; control together with brown spot; control with carbendazim and thiophanate-methyl.

Pests

Aphids These are piercing-sucking pests, often gathering on leaves, tender stems, flower buds, terminal buds and other parts, piercing and sucking sap, causing leaves to wrinkle, curl and become deformed, and in severe cases causing branches and leaves to wither. They occur frequently in spring and summer. Control methods: protect natural enemies; at the seedling stage use acetamiprid, imidacloprid, pymetrozine and pirimicarb; organophosphates such as dichlorvos, phoxim, malathion and chlorpyrifos; pyrethroid pesticides such as cypermethrin, fenvalerate and cyhalothrin.

Slugs They mostly cause damage at the seedling stage, licking and eating leaves, stems and young shoots. Control methods: during the occurrence period, use melon rind or vegetables as bait to trap and kill them, or spray fresh lime powder in the morning and evening.

Black cutworm and yellow cutworm They damage seedlings from mid-April to mid-May, biting off young stems. Control methods: capture and kill them in the early morning or use grass piles to trap and kill them.

Citrus (prickly ash) swallowtail butterfly larvae They begin to occur when seedlings are 20-25 cm tall, biting and eating leaves; after damage the leaves are incomplete. Control methods: manual capture, or at the young larval stage spray 90% trichlorfon at 800 times dilution, 2-3 times in succession.

Stinging moths The larvae bite and eat leaves. Family Limacodidae. They occur sporadically and the damage is small. Braconid wasps are their natural enemies. Control: no control may be needed; protect natural enemies; use BT and Beauveria bassiana preparations; manual capture, or at the young larval stage spray 90% trichlorfon at 800 times dilution, dichlorvos, pyrethroids, etc., for 2-3 successive treatments.

Oyster scale insects They cluster on the bark of the trunk and branches of Phellodendron and cause damage, sucking tree sap and causing poor plant development. Control methods: in April, June and July spray 16-18 times rosin mixture or 150 times methidathion emulsion, or spray 20-25 times machine oil emulsion.

Mulberry white scale They damage the trunk and branches, sucking sap. The damaged parts are covered with white flocculent material. Family Diaspididae. Control: prevent the introduction of infested seedlings; increase ventilation and light penetration; in winter brush off the insects with a bamboo brush, then spray with lime sulfur; in spring control with imidacloprid and dimethoate.

Citrus psyllid They damage leaves and tender shoots, sucking sap. They are pests of the family Psyllidae. They mainly damage citrus; Phellodendron is an important host plant. They mainly damage the tender shoots of Phellodendron, causing the tender shoots to become deformed and dry up. They are likely to occur when the tree is weak. Control: prevent the introduction of pest sources; prune and burn infested branches; control with imidacloprid, dimethoate and dichlorvos.

Leafhoppers They damage leaves and tender shoots. Family Cicadellidae. They suck sap, causing leaves to lose green color, and in severe cases cause large-scale leaf fall and weakening of the tree. They overwinter in dead leaves, have many generations, and cause widespread damage. They are a major pest and have a great impact on young trees. July to September is the peak occurrence period. Control: do a good job of controlling them in nurseries and young trees; carry out preventive control before the peak period, once every 10-15 days; control with imidacloprid, deltamethrin, dimethoate and dichlorvos.

Citrus longhorn beetle One generation per year, active during the day. The larvae bore into and feed on the cortex and xylem. Yellowish frass is often expelled outside the bore holes. This insect mostly damages the base of the main trunk and the main roots of adult trees. In severe cases the bark is bored around in a ring, destroying the transport of nutrients and water in the tree, leading to decline of tree vigor, and in severe cases causing the "girdling" phenomenon, or the death of the whole tree. Control methods: 1. Strengthen the management of the medicinal forest so that the plants grow vigorously and the trunk remains smooth, to reduce longhorn beetle egg-laying. 2. Capture and kill adults; grasp the peak activity period of adults and organize manual capture and killing. 3. Remove eggs and newly hatched larvae; pay attention to checking the sites where longhorn beetles easily lay eggs and the damage symptoms of newly hatched larvae; once found, immediately use a sharp knife to chisel and remove the eggs. At the early stage of larval occurrence, pay attention to scraping the soil to expose the root crown, check the bore holes and frass of the citrus longhorn beetle, and eliminate the larvae in the early stage of damage under the bark. 4. Hook-kill and use chemicals to poison the larvae; around the Autumn Equinox and Qingming, inspect the trees. Wherever there is frass and insect droppings, use a steel wire hook to kill the larvae. For longhorn beetle larvae that have bored deeper into the xylem, a lead strip can be made into an awl, with a small cotton ball wrapped around the tip, dipped in 80% dichlorvos emulsifiable concentrate or 40% dimethoate emulsifiable concentrate at 5-10 times dilution, and inserted into the bore hole. The above agents can also be prepared at 200 times dilution and injected into the bore hole with a syringe, then the tunnel opening sealed with poisoned mud, which can effectively kill the larvae.

Brown longhorn beetle One generation every 2-3 years, active during the day. The damage is like that of the citrus longhorn beetle, but it can also damage side branches, so some side branches can be removed to reduce the damage. Control methods: the same as for the citrus longhorn beetle.