Latest Control Methods for Common Spinach Pests and Diseases
Spinach originated in Persia and was already being cultivated 2000 years ago. The main pests and diseases of spinach include spinach white spot disease, spinach fusarium wilt, spinach downy mildew, and spinach silver-marked noctuid moth, among others. Below, the editor will briefly introduce the control methods for these common spinach pests and diseases.
Control Methods for Spinach White Spot Disease
The symptoms of spinach white spot disease mainly appear on the leaves. The lower leaves are affected first. The lesions are circular to nearly circular, with distinct edges, measuring 0.5-3.5 mm. The center of the lesion is yellowish-white, and the outer edge is brown to purplish-brown. After expansion, it gradually develops into white spots. When humidity is high, some lesions may show grayish hairy growths. When dry and wet conditions alternate sharply, the center of the lesion tends to rupture. The appearance of these symptoms is caused by infection with Cercospora beticola. This fungus can harm not only spinach but also sugar beet and other Chenopodium plants, causing similar symptoms. The spinach white spot pathogen overwinters in the soil as mycelium with diseased plant residues. The following spring, the pathogen spreads via wind and rain. It is prone to occur under weak growth, warm and humid conditions, and is more severe in low-lying, poorly ventilated areas with poor management.
[Control Methods]
1. Choose flat, well-ventilated plots with sufficient organic fertilizer for planting spinach, water appropriately, manage carefully, and improve plant disease resistance.
2. After harvest, promptly remove diseased plant residues, bury them deeply in a centralized manner or burn them to reduce sources of infection.
3. In the early stages of the disease, spray 30% Ludeobao suspension concentrate at 400-500 times dilution, or 1:0.5:160 Bordeaux mixture, 75% chlorothalonil wettable powder at 700 times dilution, or 50% duomei.
Control Methods for Spinach Fusarium Wilt
Spinach fusarium wilt generally occurs more severely during the mature plant stage. It manifests as old leaves turning dark and losing their luster, leaf mesophyll gradually yellowing and spreading upward, while downward development causes the roots to turn brown and die. Plants affected early are noticeably stunted. In dry weather with high temperatures, diseased plants rapidly wilt and yellow. Under humid and low-temperature conditions, diseased plants can survive for some time and sometimes grow new lateral roots. However, upon exposure to high temperatures, they quickly die.
The spinach fusarium wilt pathogen mainly oversummers or overwinters in the soil or on seeds with diseased plant residues. Seeds can carry the pathogen, and undecomposed manure can also carry it. The pathogen can spread with rainwater and irrigation water, directly invading through root wounds or root tips, and after invasion can reach the vascular bundles. In the vascular bundles, the pathogen produces toxic substances, blocking the vessels and causing leaves to yellow and die. High temperature and high humidity favor the disease; soil temperature around 30°C, moist soil, insufficiently decomposed fertilizer, many underground pests, and many nematodes make it prone to occur.
[Control Methods]
1. Implement a 3-5 year crop rotation with allium crops and gramineous crops, avoiding continuous cropping.
2. Apply compost fermented with Japanese enzyme bacteria or fully decomposed organic fertilizer, and adopt formula fertilization techniques to improve host disease resistance.
3. Use high ridge or raised bed cultivation, drain promptly after rain, and strictly prohibit flooding irrigation.
4. When central diseased plants are found, pull them out promptly, and drench the diseased holes and surrounding areas with 50% benomyl wettable powder at 1500 times dilution, 40% duoliu suspension concentrate at 500 times dilution, or 10% zhiweiling aqueous solution at 300-400 times dilution, spraying once every half month, for 2-3 consecutive times.
Control Methods for Spinach Downy Mildew
Downy mildew is the most frequently occurring disease of spinach. It is caused by a fungus called Peronospora spinaciae. The symptoms in the field are: it mainly affects the upper surface of leaves, with pale yellow, irregular lesions of varying sizes, 3-17 mm in diameter, with indistinct edges. After the lesions expand, they connect with each other into patches, and later turn brown and die. On the underside of the leaves, grayish-purple mold layers form on the lesions. The disease develops from outer leaves to inner leaves, and spreads from the lower part of the plant upward. In drought, diseased leaves yellow and wither; when humidity is high, they mostly rot; in severe cases, the entire plant's leaves turn yellow and die.
[Control Methods]
1. Strengthen cultivation management. Reasonable close planting, scientific irrigation, and reduce field humidity.
2. Choose disease-resistant varieties. You can use excellent varieties such as Savoy Hybrid No. 612, Barnuti, and Bonus, or use pointed-leaf type varieties.
3. Collect seeds from disease-free land or disease-free plants. If seeds carry the pathogen, they can be treated before sowing with 50% thiram wettable powder, using an amount of 0.4% of the seed weight.
4. In early spring, if diseased plants are found in the spinach field, remove them promptly, take them out of the field, and burn them.
5. In the early stages of the disease, spray 40% fosetyl-aluminum wettable powder at 200-250 times dilution, 58% metalaxyl at the stage, spray 40% fosetyl-aluminum wettable powder at 200-250 times dilution, 58% metalaxyl mancozeb wettable powder at 500 times dilution, 64% sandofan wettable powder at 500 times dilution, or 72.2% propanocarb aqueous solution at 800 times dilution, spraying once every 7-10 days, for 2-3 consecutive times.
Control Methods for Spinach Silver-Marked Noctuid Moth
The spinach silver-marked noctuid moth mainly harms vegetables such as cabbage, turnip, radish, kidney bean, and eggplant. Newly hatched larvae gather on the underside of leaves, peeling and eating the leaf mesophyll while leaving the epidermis. Older larvae disperse to cause damage, eating the leaves into holes.
[Control Methods] Generally, no separate control is needed. If the occurrence is severe, chemical control should be the main method. The best period for spraying is from the peak hatching stage of eggs to before the 3rd instar larvae, and both the front and back sides of the leaves should be sprayed. The pesticides used include: 10% permethrin EC at 1000-1500 times dilution, or 2.5% deltamethrin EC at 2000-3000 times dilution, or 20% fenpropathrin EC at 3000 times dilution, or 2.5% bifenthrin EC at 3000 times dilution, or 10% fenvalerate-malathion EC at 1500-2000 times dilution, or 50% phoxim EC at 1000-1500 times dilution, etc.