Broccoli Pest and Disease Control Methods and Technical Key Points
Broccoli is an annual or biennial herbaceous plant, native to the eastern Mediterranean coastal region. It is cultivated in small quantities in China, mainly for use in Western cuisine. Broccoli is nutrient-rich, containing protein, sugar, fat, vitamins and carotene, and ranks first among vegetables of its kind in nutritional content, and is known as the “crown of vegetables”. It is a variety of the cabbage species in the genus Brassica of the family Brassicaceae, with the green flower head as its product. It originated in the Mediterranean coastal area of Europe, in the region of Italy, and was introduced to China at the end of the 19th century.
The main diseases of broccoli at the seedling stage are damping-off and Rhizoctonia rot.
Symptoms of broccoli damping-off
After the seeds germinate but before emergence, infection mostly causes seed rot; after emergence, infection causes a water-soaked appearance near the soil surface, softening, easy peeling of the epidermis, constriction of the diseased part, rapid expansion around the stem, lodging of the seedlings, and patchy seedling death. Pathogen of broccoli damping-off
Pythiumaphanidermatum(Eds.)Fitzp. is called cucurbit fruit rot Pythium, belonging to the oomycetes. The mycelium grows luxuriantly, appearing as white cottony fluff; the hyphae are colorless, non-septate, with a diameter of 2.3-7.1 micrometers. The distinction between hyphae and sporangiophores is not obvious. The sporangia are filamentous or branched-lobed, or irregularly swollen. Size 63-725×4.9-14.8 micrometers. The vesicle is spherical, containing 6-26 zoospores. The oogonium is spherical, diameter 14.9-34.8 micrometers; the antheridium is pouch-shaped to broadly club-shaped, borne on the same hypha or different hyphae, mostly 1. Size 5.6-15.4×7.4-10 micrometers. The oospore is spherical, smooth, not filling the oogonium, diameter 14.0-22.0 micrometers. This fungus appears more frequently in places with high average annual temperature. In addition, P.spinosumSaw. is called spiny Pythium, belonging to the oomycetes. It is also a pathogen of this disease. On CMA it has no special shape. On PCA it is slightly radial. The main hypha is 8.0 micrometers wide, spreading between or within cells: the sporangia are spherical or nearly spherical, smooth or spiny, terminal or intercalary, size 14-33 micrometers, producing 1-3 germ tubes upon germination, with no zoospores observed; the oogonium is spherical to subspherical, densely covered with finger-like spines of uniform thickness from top to bottom, varying in length, straight and not curved, with individual spines few or absent, size 17-24 micrometers, terminal or intercalary; 1 antheridium, typically borne on the same hypha with a stalk, the antheridium borne within the oogonium stalk or the main rod hypha, size 12-32×3-5 micrometers: the oospore fills the oogonium, occasionally nearly filling it, the oospore is colorless, spherical, size 12-21 micrometers. According to testing in Ningxia, the seedling death rate caused by this fungus in pepper damping-off accounted for 83%; cucurbit fruit rot Pythium accounted for 84%; ultimate Pythium accounted for 80%.
Control methods for broccoli damping-off:
(1) In areas where damping-off is mainly caused by the high-temperature-loving fungus P.aphanidermatum, 0.2% of 40% seed dressing double powder can be used for seed dressing or soil treatment. The method of chemical soil treatment to cultivate strong seedlings and prevent damping-off is: after sowing, cover with a layer of nutrient soil, water thoroughly, then cover with film to keep warm and moist; after emergence, spray 0.2%-0.3% potassium dihydrogen phosphate 2-3 times to enhance disease resistance; if necessary, spray 25% Ridomil wettable powder 800 times solution;
(2) For damping-off caused by A.brassicicola, it is recommended to use 0.2-0.3% of 75% chlorothalonil wettable powder or 70% mancozeb dry suspension powder or 60% Fenbingbao (carbendazim hydrochloride) ultra-fine wettable powder for seed dressing. The control effect is better than soil treatment or irrigation. (3) If necessary, irrigate with 69% Anke mancozeb wettable powder 900 times solution.
Symptoms of broccoli Rhizoctonia rot
Broccoli Rhizoctonia rot, also known as black root disease, is an important seedling-stage disease of broccoli. In the early stage of the disease, the root-stem part of the seedling turns black or constricts; when moist, a gray-white mold-like substance grows on it. After the plant is infected, within a few days the leaves wilt and dry up, and then the whole plant dies. After transplanting, it generally stops spreading. But in some fields, seedling death continues. In addition, the disease can also appear as damping-off-like symptoms or head rot. Pathogen of broccoli Rhizoctonia rot
RhizoctoniasolaniKühn is called Rhizoctonia solani AG2-1 and AG-4 hyphal anastomosis groups, belonging to the Deuteromycetes fungi. Its sexual state is Thanatephoruscucumeris(Frank)Donk., called cucumber death fungus, belonging to the Basidiomycota fungi. Before fusion, the hyphae are often mutually attracted, forming three fusion states: complete fusion, incomplete fusion, and contact fusion. More than ten hyphal anastomosis groups have been discovered and established in China, among which AG-4 is the dominant group causing damping-off of cucumber, winter melon, etc., and banded sclerotial blight of corn, and is an important group. It has a wide host range and causes diseases in many crops. The strains of the AG-4 hyphal anastomosis group are further divided according to sclerotium morphology and DNA nitrogen base sequence homology into two subgroups, AG-4HG-I and AG-4HG-II. The former forms dark brown sclerotia on PDA medium, while one-third to one-half of the latter forms gray to white-brown sclerotia. Rhizoctonia solani is divided into three major groups. One group is the multinucleate Rhizoctonia solani, with 3 or more nuclei, relatively large hyphae, about 6-10 micrometers in diameter, whose sexual state is Thanatephoruscucumerls(Frank)Donk., called cucumber death fungus. In soil it forms a thin waxy or white-pink reticulate to net-like hymenium, producing basidia that are barrel-shaped to subcylindrical, slightly wider than the supporting hyphae, with the basidia bearing 3-5 sterigmata on which basidiospores are borne; the basidiospores are elliptical to broadly club-shaped, wider at the base, size 7.5-12×4.5-5.5 micrometers, and the basidiospores can germinate repeatedly, forming secondary basidia on the basidium. Rhizoctonia solani is formed by dense branching of the tip of a single hypha or by tight clustering of tips and hyphae to form hyphal knots. Different hyphal anastomosis groups are not completely identical in morphology, pathology, physiology and ecology. As for the pathogenic specificity of each anastomosis group and their internal connections and roles in nature, further clarification is still needed.
Control methods for broccoli Rhizoctonia rot:
(1) For spring cultivation, it is advisable to choose varieties that are not very sensitive to low temperatures in the early growth stage. Such as Luling, Ludi, Qinglu, Zaoshenglu, Bisong, Bishan, Lühua No. 2, Zhengyanshui, Shanghai No. 1, etc.
(2) Cabbage seed coating and film wrapping. Add 0.1% oxytetracycline or 3% of 75% chlorothalonil into the film-forming liquid, stir evenly, then mix at a ratio of 30 parts seeds to 1 part medicinal liquid, and use after drying. This can prevent diseases caused by seed-borne pathogens in cabbage-type vegetables.
(3) Sow at the appropriate time, not too early or too late.
Diseases during the growth period include downy mildew, viral disease, sclerotinia disease, black rot, soft rot, etc. Agricultural control methods include: 1. Select disease-resistant varieties. 2. Apply fully decomposed organic fertilizer and balance the application of nitrogen, phosphorus and potassium. 3. After harvest, clean the field in time, remove plant residues and fallen leaves, etc., and take them out of the field for deep burial or burning. Chemical control methods include: 1. Downy mildew: at the early stage of disease, use 50-75 g of Yimeng in 15 kg water, or 15-20 g of Ridomil in 15 kg water, or 60% Mieke or 64% Sandofan or 58% Ridomil or 72% Kelu 500-600 times for spray control. 2. Viral disease: using Bingdujing, Bingdubisi, etc. 15-20 g in 15 kg water has a relatively good control effect. 3. Sclerotinia disease: at the early stage of disease and on rainy days, spray 50% iprodione 1000 times or 50% sumilex 1500 times. 4. For black rot and soft rot, after transplanting and survival, spray 80% Bibei 500 times or 77% Kechade 500 times or 47% Jiaruinong 800 times.
The main pests of cauliflower are aphids, cabbage caterpillars, etc., which can be controlled alternately with Lesiben (chlorpyrifos), pirimicarb, trichlorfon, Shachongwang, etc.