Detailed Explanation of Control Techniques for Major Diseases and Pests of Perilla

Perilla (Perilla frutescens var. crispa) is an annual herbaceous plant of the genus Perilla in the Lamiaceae family, also known as guiren, suzi, shansu, chisu, heisu, baisu, and huihuisu, and is called "su" in the Erya Shicao. It is not only a nutrient-rich specialty vegetable, but also a traditional Chinese medicine with good efficacy, and a widely used industrial raw material, with fairly broad prospects for development. However, in high-yield cultivation, some diseases and pests are often found to cause damage, and the common major ones are as follows:

I. Major Diseases

I. Rust: Rust is caused by fungi of the genus Uredo, and the pathogen mainly overwinters in the soil with diseased plant residues, infecting and causing disease the following year; a large number of urediniospores are released from the lesions and spread by airflow and rainwater. Generally, the disease is more severe in the rainy season, and low-lying fields with poor drainage and plots with overly dense planting and poor ventilation and light transmission are also more prone to the disease. It mainly damages leaves. When the leaves first develop the disease, yellow-white spots appear on the underside of the leaves from bottom to top, then expand to the whole plant; in the later stage, the lesions rupture, releasing orange-yellow or even black powdery material, until the leaves wither and fall off, and the plant dies prematurely. Its control methods:

1. Agricultural technical control: Implement crop rotation to avoid continuous cropping; choose plots with high terrain and good drainage for planting, or make raised beds, pay attention to clearing ditches and draining water to reduce field humidity; apply sufficient decomposed farmyard organic fertilizer and increase phosphorus and potassium fertilizer to improve disease resistance; plant at a reasonable density and remove leaves and side branches in time to facilitate ventilation and light transmission; after harvest, promptly remove diseased plant residues and bury them deeply or burn them to prevent the pathogen from remaining and spreading.

2. Chemical control: Before sowing, dress seeds with 15% triadimefon at 0.4% of seed weight; at the initial stage of disease, spray 1:1:200 Bordeaux mixture 2-3 times; or spray 25% triadimefon 2,000-fold solution, or 15% triadimefon 1,000-fold solution, or 25% propiconazole 4,000-fold solution, once every 15-20 days; or use 97% nabam 250-fold solution, or 50% dinitro compound 200-fold solution, or 50% sulfur suspension concentrate 400-500-fold solution, once every 7-10 days, spraying 2-3 times continuously.

II. Leaf spot: Leaf spot is also caused by fungal infection, and the pathogen mainly overwinters on diseased plant residues and seeds. When the temperature is 20-25°C and the relative humidity is above 90%, the disease is favored. Continuous cropping fields, low-lying fields, excessive watering, poor drainage, and overly dense planting plots suffer severe disease. It generally occurs in early summer and lasts until late autumn. At the initial stage of disease, small brown or black spots appear on the leaf surface, gradually expanding into large lesions, and after drying, holes form, until the leaves fall off. Its control methods:

1. Agricultural control: Select good disease-resistant varieties, pay attention to retaining seeds from disease-free plants to prevent seed-borne disease; pay attention to crop rotation to avoid continuous cropping; apply sufficient fully decomposed farmyard manure and increase phosphorus and potassium fertilizer to improve plant disease resistance; pay attention to drainage during the rainy season to reduce field humidity; planting should not be too dense, remove leaves and side branches in time, and improve ventilation and light conditions; promptly remove diseased plant residues in the field to reduce sources of inoculum.

2. Chemical control: At the initial stage of disease, spray 1:1:200 Bordeaux mixture, or 65% zineb 700-fold solution, or 70% mancozeb 500-fold solution, or 58% metalaxyl-mancozeb 400-fold solution, or 75% chlorothalonil 500-fold solution, or 50% carbendazim 500-fold solution, or 50% thiophanate-methyl wettable powder 500-fold solution.

III. Root rot: This is a fungal disease, mainly spread by rainwater, undecomposed farmyard manure, and farm tools. Under conditions of high temperature and high humidity, low-lying waterlogged areas, heavy clay soil, and many years of continuous cropping, the disease is severe. It damages the root and stem; the main root is damaged and rots, no lateral roots are produced, the plant is stunted, and in severe cases the stems and leaves wither and die. Its control methods:

1. Agricultural control: Implement crop rotation, with no continuous cropping for more than 3 years; before sowing in the seedbed, fully turn and sun the soil, apply sufficient decomposed manure, and cultivate disease-free strong seedlings; use deep furrows and high beds, do a good job of drainage, and improve the field ecological environment; burn diseased plants in a centralized manner, and disinfect the affected area with lime.

2. Chemical control: At the initial stage of disease, spray 50% thiophanate-methyl wettable powder 500-fold solution, or 75% chlorothalonil 600-fold solution, or 75% dexon 1,000-fold solution, or 40% carbendazim-sulfur suspension concentrate 800-fold solution. Mainly spray the root and stem area, about once every 7 days, spraying 2-3 times continuously.

IV. Powdery mildew: Commonly known as white mold disease, it is a fungal disease. The pathogen overwinters on field diseased residues and becomes the initial infection source the following year. The suitable temperature for disease onset is 16-24°C. When high temperature and high humidity alternate with high temperature and drought, and plant vigor is weak, the disease is severe. Its control methods:

1. Agricultural control: In severely diseased fields, implement rotation with non-host crops for more than 2 years; choose fields with higher terrain and good drainage for planting; apply sufficient decomposed livestock and poultry manure and cultivate strong seedlings; pay attention to field ventilation and light transmission to reduce humidity; strengthen fertilizer and water management to prevent excessive vegetative growth or premature senescence due to nutrient deficiency; burn diseased plant residues to eliminate sources of inoculum.

2. Chemical control: At the initial stage of disease, spray 25% triadimefon 2,000-fold solution, or 15% triadimefon 1,000-fold solution, or 40% carbendazim-sulfur suspension concentrate 500-fold solution, or 50% thiophanate-methyl suspension concentrate 500-fold solution, once every 7-10 days, spraying 2 times continuously; alternatively, at the very beginning of disease, immediately spray baking soda 500-fold solution, once every 3 days, for 4-5 times continuously, all of which can control the damage.

V. Dodder: In some high-yield perilla fields, patches of perilla plants can sometimes be seen tangled and bent in all directions by many golden-yellow thin strands, with leaves turning yellow and wilting. This is the holoparasitic seed plant - dodder, which absorbs nutrients from the perilla body, nourishes itself, and damages or even kills the perilla. Its control methods:

1. Agricultural control: Take care not to use seeds from diseased fields, carefully select perilla seeds, or remove dodder seeds mixed among perilla seeds before sowing to prevent dodder from being mixed in; manure should be fully fermented at high temperature, and dodder seeds mixed into the manure must be rotted; hoe the field to eliminate dodder after it germinates but before it twines around perilla; when scattered dodder twining is first seen, seize the time before flowering and seed setting to thoroughly remove the dodder vines and burn them all, so as to eliminate future trouble.

2. Chemical control: When dodder is young, use a stick to break its stems and vines, and on cloudy days or in the evening, spray the "Lubao No. 1" microbial agent containing no fewer than 30 million viable spores per milliliter of water; after sowing perilla and before emergence, use 0.23 kg of lasoo emulsifiable concentrate or 0.4 kg of napropamide emulsifiable concentrate per mu, add 100 kg of water, and spray.

II. Major Insect Pests

I. Red spider mite: It mainly pierces and sucks perilla leaves and young parts, especially in the middle and late stages of perilla growth, causing severe damage, resulting in plant deformity and premature senescence. Its control methods: