Cockroaches, often mistaken for true cockroaches, are actually the larvae of Scarabaeoidea beetles belonging to the order Coleoptera. Since 1995, these pests have been causing significant damage to Zoysia japonica (commonly known as Taiwan grass) and Lyprantha macrophylla (carpet grass), with infestations becoming increasingly severe in certain areas. The affected grasslands continue to suffer year after year, leading to a growing concern that cockroaches have now become one of the most serious threats to turfgrass ecosystems.
**First, Understanding Their Habits and Infestation Patterns**
These pests primarily feed on grass roots within the top 10 centimeters of the soil surface. In extreme cases, they completely destroy the root systems, leading to the death of the grass. Several factors contribute to their population growth and spread:
1. **Soil Texture and Composition**: Earthworms thrive in loose, sandy soils with high sediment content. For instance, the Dayeyou grassland in Haixia Park has more than 50% sediment, while the severely damaged Nanwan Avenue area contains up to 60% sand. These conditions create an ideal habitat for them.
2. **High Organic Matter Content**: The soil in the Nanwan Avenue area is sandy but rich in organic matter, which has accumulated over eight years of continuous grass growth. Dead grass roots left underground provide a constant food source for the larvae.
3. **Low Soil Moisture**: According to reports from garden staff, insufficient watering has worsened the infestation, making the environment more favorable for earthworm activity.
4. **Long-Term Grass Growth**: Many grasses affected by earthworms are over four years old, with thick root systems that provide ample food and shelter for the pests.
**Second, Control Methods**
**(a) Agricultural Control**
1. **Soil Replacement**: To prevent future infestations, it's recommended to replace contaminated soil with clay in areas where damage has been severe. This involves removing the turf and replacing the top 15–20 cm of soil with clay to create an unfavorable environment for the pests.
2. **Planting Cover Crops**: Using ramie or other plants along roadsides and wastelands can help suppress adult populations by poisoning them.
3. **Manual Removal**: Shaking trees to manually collect and kill adult insects is also an effective method in some cases.
**(b) Physical Control**
Using the phototactic behavior of adult earthworms, black lights or dual-lamp systems (half black light, half green light) can be used to attract and trap them during their active periods.
**(c) Chemical Control**
Chemical methods remain the primary approach for controlling these pests:
1. Apply 3% carbofuran at 7–10 pounds per acre mixed with 30–50 pounds of sand and water. This helps the chemical penetrate the soil and reach the larvae.
2. Use 3% methyl isophosphorus granules at 10–14 pounds per acre, mixed with sand and water for application.
3. Apply 6% lindane at 2–3 pounds per acre, mixed with sand and water.
4. Mix 50% phoxim EC at 0.4–0.5 kg per mu with fine sand (30–50 kg) after diluting it with 10 times the volume of water. Spray the mixture onto the sand and then apply it to the grass.
**(d) Biological Control**
Biological control is a promising and environmentally friendly strategy:
1. Fungi such as *Beauveria tenella* and bacteria like *Bacillus thuringiensis* (known as Doom and Japedemic in the U.S.) can be used to infect and kill the pests.
2. Insecticidal nematodes (*Steinernema* species) are effective against larvae in the soil.
3. Bumblebees and parasitic wasps such as *Prosenasiberita Fabricius* can also be introduced to naturally control the population.
In conclusion, a combination of agricultural, physical, chemical, and biological control methods is essential for long-term management of this pest. Continued research and adaptation of these strategies will be key to protecting grasslands from further damage.
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