What are the common pest and disease control methods for oilseed peony?

Oilseed peony is a woody oil crop with high yield, high oil content, high quality and low cost. It is prone to pest and disease damage during cultivation. What common pests and diseases affect oilseed peony? How to control them?

Common diseases of peony include anthracnose, brown spot, rust, violet root rot and leaf spot, while pests include scale insects, scarab beetles, red spider mites, cabbage caterpillars and so on. Below is an introduction to the control methods for common pests and diseases of oilseed peony, for reference only by growers.

Main diseases

1. Peony gray mold

Gray mold is one of the important peony diseases worldwide, and it also occurs from time to time in China, being relatively severe in Shanghai, Zhengzhou and other places. The disease can occur throughout the growing season of peony, causing serious damage to young and tender plants, leading to lodging and wilting of seedlings, brown spots on the leaf surface with irregular concentric rings. When the weather is humid, gray mold grows on the lesions, brown markings form on the flowers, and if flower buds are damaged they cannot bloom. The control methods are as follows:

(1) Reduce sources of infection

In autumn, remove dead branches and fallen leaves of diseased plants; during spring when the disease occurs, remove diseased buds and leaves, and bury the diseased residues deeply.

(2) Chemical control during the growing season

Once the disease occurs during the growing season, the following agents can be used for spray control: 1% lime equivalent Bordeaux mixture, 70% thiophanate-methyl 1000x solution, 65% zineb 500x solution, 50% chloronitrofen 1000x solution. Spray once every 10-15 days for 2-3 consecutive applications.

(3) Strengthen cultivation management

Plant at appropriate density; drain promptly after rain, and do not mound wet soil around the base of the plants; practice crop rotation in severely affected areas; plant disease-free seedlings, and soak seedlings in 65% zineb 300x solution for 10-15 minutes.

2. Peony brown spot

Brown spot, also called red spot, is a common peony disease worldwide. It occurs mostly after flowering, between the summer solstice and the beginning of autumn, and worsens from mid-October as temperatures rise. In the early stage of the disease, small yellow or yellow-brown spots appear on the leaf surface, turning into black spots after 1-3 days, then expanding into irregular concentric rings; in severe cases the entire leaf withers and falls off. It spreads especially rapidly in hot, dry weather, often infecting an entire plot, seriously affecting peony growth. The control methods are as follows:

(1) Reduce sources of infection. Thoroughly remove diseased residues above ground in autumn. Bordeaux mixture can be sprayed before the disease occurs, and carbendazim sprayed in the early stage. Before the plants sprout in early spring, spray 50% carbendazim 600x solution or 3 degrees Baume lime sulfur mixture to kill the pathogens on the plants.

(2) Chemical control during the growing season. After the disease occurs, spray 50% carbendazim 1000x solution or 65% zineb 500-600x solution, once every 7-10 days for 3-4 consecutive applications.

(3) Strengthen cultivation management. Plant at appropriate density and apply organic fertilizer and compound fertilizer.

3. Peony anthracnose

Anthracnose is a common peony disease in China, being relatively severe in Beijing, Shanghai, Wuxi, Zhengzhou, Xi'an and other places. It is also relatively severe in the United States and Japan. It has also been reported in the United States, Japan and other countries. Anthracnose often causes contiguous blighted spots on peony leaves, twisted diseased stems, and death of young tender branches.

In the early stage of the disease (May-June), spray 70% thiram 500x solution, or 1% lime equivalent Bordeaux mixture, or 65% zineb 500x solution. Spray once every 10-15 days, for a total of 2-3 applications.

4. Peony ring spot

Ring spot, also called white star disease, is another common leaf spot disease of peony, being relatively severe in Changsha, Zhengzhou, Guiyang, Beijing and other places. The control methods are as follows.

(1) Reduce sources of infection. Promptly remove diseased branches and fallen leaves; before the plants sprout, spray 3 degrees Baume lime sulfur mixture to kill the pathogens on the peony plants.

(2) Chemical control during the growing season. Spray 1% lime equivalent Bordeaux mixture, or 50% thiram 800x solution, or 65% zineb 500x solution. After the disease occurs, spray 2-3 consecutive applications (once every 10-15 days).

(3) Strengthen cultivation management. Appropriate planting density and good ventilation and light penetration.

5. Peony branch blight

Peony branch blight can infect the stems, branches and other parts of peony. When it occurs on stems, brown lesions mostly appear, which then expand year by year into red elliptical lesions; the lesions can encircle the stem, causing the branches above the lesion to die rapidly. In autumn, black small dots appear on the lesions, which are the pathogen's pycnidia. Buds become brown when infected, and dead buds can remain on the plant for a long time.

The disease is caused by fungi. The pathogen mainly invades through wounds. When there are many wounds and the plant grows weakly, the disease occurs. Therefore, cultivation management should be strengthened to enhance growth vigor and reduce wounds, thereby improving plant disease resistance.

Control methods: refer to peony brown spot.

6. Peony root-knot nematode disease

Peony root-knot nematode disease is relatively common and has been reported both in China and abroad. In the past ten-plus years, root-knot nematode disease has occurred to varying degrees in Henan, Shandong, Beijing, Jiangsu and other provinces in China, and has become the most important disease threatening peony roots in China. In severe cases, all peony leaves fall off by August, and successive years of occurrence can lead to plant dwarfing, small leaves, small flowers or no flowering at all.

(1) Strengthen quarantine to prevent expansion of affected areas. When diseased seedlings are found during introduction work, they must be treated: soak in 0.1% isofenphos-methyl for 30 minutes, or soak in warm water at 48-49°C for 30 minutes.

(2) Field chemical control. Apply 15% aldicarb granules in holes, 5-10 g per plant, hole depth about 10 cm, apply once a year in early May.

(3) Treatment of diseased soil

Disinfect with heat or pesticides. Commonly used pesticides include methyl bromide, aldicarb, fenamiphos and so on. Soil can also be disinfected by drying and high-temperature sterilization; for example, after pots are dried for 30 days (moisture content reaching 0.17%), no nematodes survive.

7. Powdery mildew

In the early stage of the disease, a layer of white powdery spots forms on the upper surface of leaves; later, dirty-white powdery layers appear on both sides of the leaves and on the petioles, with many small black dots scattered within, which are the pathogen's cleistothecia. In Luoyang and other places it generally begins in early May and gradually worsens. Late August is the peak period of the disease, after which diseased leaves gradually wither and fall off.

To control this disease, spray 20% triadimefon 1500x solution in the early stage, once every half month, with 2 consecutive applications giving significant results.

8. Root rot

According to testing, root rot is caused by a fungus invading the medicinal peony plant. In the initial stage the disease is difficult to detect; by the time abnormal signs are visible on the leaf surface, the root bark is mostly rotted to black, and yellow reticular mycelium is often present in the soil around the diseased plant's roots. This is a common disease; in the early stage of infection the leaves shrink, then fall off, and finally the whole plant dies. If not controlled in time, it will spread to surrounding plants. It spreads especially rapidly on rainy days when the soil is too wet.

For control, the plot should be turned over and sun-dried. After the disease is found, promptly remove the diseased plants and the surrounding pathogen-bearing soil, and irrigate the surrounding plants with 1:100 ferrous sulfate solution to prevent spread of infection.

Main pests

The most common peony pests include: stem borers, white grubs, inchworms, tortrix moths, mite larvae, as well as white ants and cutworms.

Cottony cushion scale

Cottony cushion scale is one of the main pests of peony. This pest is prone to occur in peony gardens with excessive planting density and touching branches and leaves, or on indoor potted peonies with poor ventilation. In severe cases it not only makes peony flowers small and reduces flowering, but also causes peony leaves to fall off and even the whole plant to die.

The scale insect belongs to the genus Icerya in the family Margarodidae, superfamily Coccoidea, order Homoptera. The female is 5-7 mm long, oval, orange-red; the back is raised with many wrinkles and white waxy secretions; the abdomen is flat with a white waxy egg sac. It mostly attaches to branches or leaves to suck peony sap. It overwinters as fertilized females. After peony leaves fall, white patch-like insect bodies can be seen distributed over the whole plant on the branches.

Winter is the best time to control peony cottony cushion scale. Use a bamboo knife to scrape off all insect bodies from the branches and burn them, and apply 3-5 degrees Baume lime sulfur mixture or Supumie 1000x solution to the branches to kill overwintering females and eggs. If some insect bodies remain alive after winter control, spray 50% omethoate or malathion 1000x solution in March-April of the following year when the larvae first hatch, spraying 2-3 consecutive times to kill this pest relatively thoroughly.

White grubs

These are the larvae of scarab beetles, mostly white, with many wrinkles, curving into a "C" shape when at rest, with a yellow-brown or orange-yellow head. The adults are scarab beetles, with many wrinkles, damaging peony roots. They chew germinating seeds underground and bite off seedling roots and stems, causing the whole plant to die, and in severe cases causing missing plants and broken rows.

To prevent white grubs from biting peony roots, use black light traps to kill adults in April-May, spread 250 g of 5% phoxim granules per mu, or use 50% phoxim 1000x solution for root irrigation. Turn the soil before overwintering, and use omethoate for root irrigation to eliminate larvae and winter pupae; during the peak period of adults, spray 90% trichlorfon, 80% dichlorvos, 40% omethoate, 50% malathion and other 1000-1500x solutions.

Stem borers

The larvae bore into roots and stems to feed, and after damage the plant's leaves turn yellow and wilt. During the peak period of the first-generation larvae of stem borers, use medicated cotton balls to plug the calyx tube to effectively kill the eggs. Commonly used pesticides include 90% trichlorfon and 80% dichlorvos 1000x solution.

Red spider mites

These insects are very small, less than 1 mm long, round or oval, orange-yellow or red-brown. Because they are small they are hard to find, and once damage is noticed the flowers are often already severely affected. This insect damages plants by piercing the leaf with its mouthparts and sucking sap, destroying chlorophyll, causing grayish-yellow spots or patches on the leaves, and making leaves wither, fall off or even drop completely. Commonly used pesticides for control include propargite, dicofol, dimethoate, huachongjing, fenvalerate and so on. For home flower growing, prepare a flower sprayer and add 4 drops of propargite or fenvalerate or huachongjing to 400 ml of water (equivalent to 2000x solution), or add 8 drops of dicofol or dimethoate (equivalent to 1000x solution). Shake well after adding the pesticide, then spray immediately; spraying should be uniform and thorough, especially the undersides of leaves. When spraying, it is best to move potted flowers outdoors; if spraying indoors, do not go near food or other utensils.

Aphids

Aphids are distributed in farmlands, grasslands, orchards and forest areas. They are the most common insects on many cultivated plants or weeds, as well as in vegetable gardens. Both adults and nymphs can feed on plant sap with their piercing-sucking mouthparts, not only hindering plant growth and causing wilting, but also transmitting plant diseases, causing great damage and losses.

The greatest morphological feature of aphids is a pair of spike-like honey tubes on the dorsal side of the soft abdomen, from which honeydew is secreted; ants that relish honeydew thus form a symbiotic relationship with aphids.

To control aphids, spray 10% omethoate emulsion 1000x solution, or malathion emulsion 1000-1500x solution, or dichlorvos emulsifiable concentrate 1000x solution.

When oilseed peony is attacked by pests and diseases, it affects plant growth and oil production rate, so growers should pay attention. The above are the common pests and diseases of oilseed peony and their control methods. We hope this is helpful to you. To learn more agricultural technical knowledge, please follow Huinong Network!

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