Distribution and fixed-precision sampling plans for diamondback moth (Lepidoptera: Plutellidae), on winter-spring...

Area of Science:

• Agricultural Entomology
• Pest Management
• Crop Protection

Background:

• Diamondback moth (Plutella xylostella) is a major pest of cabbage, leading to extensive insecticide application.
• Lack of standardized sampling plans necessitates indiscriminate pesticide use by farmers.
• Pest infestations cause significant yield losses across all cabbage growth stages.

Purpose of the Study:

• To develop fixed-precision sampling plans for Plutella xylostella management on winter-spring cabbage.
• To establish action thresholds (ATs) for P. xylostella based on population density.
• To evaluate the potential for a unified sampling plan across different growing seasons.

Main Methods:

• Population monitoring involved weekly counts of immature P. xylostella on 60 cabbage plants over 11 weeks for two seasons.
• The mean density-variance relationship was used to characterize pest distribution.
• Fixed-precision sampling plans and action thresholds were developed using infested plant counts.

Main Results:

• A high aggregation of P. xylostella was observed in spring compared to winter.
• An average of 35 plants were needed to estimate pest density within a 15% standard error.
• Sampling plans led to substantial reductions in insecticide treatments (100% in winter, 45% in spring).

Conclusions:

• A single, practical sampling plan for P. xylostella is feasible across cabbage growing seasons.
• Developed action thresholds align with established integrated pest management (IPM) programs, indicating reliability.
• Implementing these sampling plans can significantly decrease reliance on chemical insecticides.