Management of Crown Mite in Spinach: Symptoms, Treatment, Chemical, Biological, Natural, and Organic Control

The spinach crown mite (Schizotetranychus celarius) is a tiny, almost transparent mite that can cause significant damage to spinach crops. It is most commonly found in soils high in organic matter and under cool, moist conditions. These conditions provide an ideal environment for the mites to proliferate and feed on the newly expanding leaves at the heart of the plant.

Crown mites are difficult to control because they can survive in soils after removing the crop and consuming organic matter to sustain themselves. This makes it challenging to eradicate them from the field, even using pesticides or other control methods.

Management of Crown Mite in Spinach

The Life Cycle of Crown Mite

Egg stage: The transparent, spherical eggs are laid in the innermost parts of the plant. The eggs hatch in 2-4 days, depending on the temperature.
Larva stage: The newly hatched larvae have six legs and are translucent. They feed on plant tissue and molt to the next stage after 1-2 days.
Protonymph stage: The protonymphs are similar in appearance to the adults but smaller in size. They have eight legs and feed on plant tissue. They molt to the next stage after 1-2 days.
Deutonymph stage: The deutonymphs are similar in appearance to the adults but still smaller in size. They have eight legs and continue to feed on plant tissue. They molt to the adult stage after 1-2 days.
Adult stage: The adult crown mites are small, nearly transparent, with noticeable long hairs. Both the soil and the crowns of vulnerable plants contain them. They deposit eggs on the new growth and reside deep within the spinach plant’s crown. Throughout their existence, which can be as little as ten days in warm climates, the females can deposit up to 60 eggs. The full life cycle from egg to adult can be completed in as little as 5-7 days in warm conditions, causing rapid population expansion and crop infestation.

Identification of Crown Mite in Spinach Field

Look for symptoms of crown mite infestation: The symptoms of crown mite infestation include stunted growth, yellowing of leaves, distorted growth, and reduced yield.
Inspect the innermost parts of the plant: Crown mite eggs are transparent and spherical, laid in the plant’s innermost parts. Inspect the plant’s crown and the stem’s base to see if any eggs are present.
Look for adult mites: Adult mites are tiny, almost transparent, and have prominent long hairs. They can be found in the soil and susceptible plants’ crowns.
Look for protonymphs: Protonymphs are immature mites similar to adults but smaller.
Check for mite movement: Use a magnifying glass to observe the movement of the mites. Crown mites are slow-moving and tend to stay in one place.

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Damage Symptoms of Crown Mite in Spinach field

Damage to seeds and seedlings: Crown mites can damage sprouting seeds and seedlings before or after emergence. The damage may include stunted growth, distorted leaves, and reduced seedling vigor.
Damage to newly expanding leaves: Crown mites feed primarily on newly expanding leaves at the heart of the plant, causing damage that appears as deformed leaves or small holes in expanding leaves.
Vector for plant pathogens: Crown mites can act as a vector for plant pathogens such as Pythium sp and Rhizoctonia sp, which can cause additional damage to the plant.

Management of Crown Mite in Spinach by Cultural Method

Crop rotation: Crop rotation can be used to manage crown mite populations. Planting non-host crops in the infested field for a time can help reduce the population of crown mites.
Use of row covers: Row covers can exclude egg-laying female crown mites from the plants. This can be an effective way to prevent the infestation of young spinach plants.
Maintain good field hygiene: Good field hygiene practices such as removing plant debris, reducing soil moisture, and avoiding over-fertilization can help to reduce the population of crown mites in the field.

Management of Crown Mite in Spinach by Biological Method

Introduction of predators: Predatory mites, predatory thrips, Oligota sp., Orius sp. (pirate bug), and mirid bugs are natural predators of crown mites. Introducing these predators to the field can help control the crown mite population.
Use of insectary plants: Insectary plants such as clover, fennel, and dill can be planted in the spinach field to attract and maintain populations of predatory insects.
Use of microbial agents: Microbial agents such as Bacillus thuringiensis and Beauveria bassiana can be used to control crown mites. These agents can be applied to the soil or foliage to infect and kill the mites.

Management of Crown Mite in Spinach by Chemical Method

Some chemicals commonly used for controlling mites and pests in spinach include abamectin, dimethoate, and rotenone. These chemicals can be applied through various methods such as ground, air, or chemigation.
Dimethoate, applied at a median rate of 0.25 lb. a.i. Per acre, it can be effective against spinach pests, including leafminers and green peach aphids. The label PHI is 14 days, but the typical PHI is 16 days.
Rotenone, applied at a median rate of 0.004 lb. a.i. Per acre, No PHI is specified on the label.
Abamectin, applied at a median rate of 0.01 lb. a.i. However, up to two applications per growing season are recommended per acre.

Preventive Measures for Control of Crown mite in Spinach field

Avoid planting next to infested fields: As crown mites can survive in soils after the crop has been removed, it is important to avoid planting spinach in fields that have been previously infested with crown mites. Planting in a different location can help to reduce the risk of infestation.
Avoid excessive use of pesticides: Excessive use of pesticides can harm the natural predators of crown mites and disrupt the ecological balance in the field. Therefore, using pesticides judiciously and only as a last resort is important.

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Conclusion

Various methods are available for managing Crown mites in spinach, including biological, cultural, and chemical methods. Biological methods involve using natural predators to control mite populations, while cultural methods involve crop rotation and field sanitation.

Chemical methods involve using pesticides, such as abamectin, dimethoate, and rotenone, but these should always be used per label instructions and regulations. Overall, effective management of Crown mites in spinach requires a combination of approaches and regular monitoring to prevent outbreaks and minimize crop damage.

Management of Crown Mite in Spinach: Symptoms, Treatment, Chemical, Biological, Natural, and Organic Control

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