Cereal aphid colony turnover and persistence in winter wheat

Area of Science:

• Agricultural Entomology
• Ecosystem Dynamics
• Pest Management

Background:

• Understanding spatial and temporal dynamics is crucial for effective crop management and integrated farming.
• Aphid pests, Sitobion avenae and Metopolophium dirhodum, pose significant threats to winter wheat production.
• Knowledge of pest distribution aids in developing targeted and sustainable agricultural strategies.

Purpose of the Study:

• To investigate the spatial and temporal distribution patterns of two key aphid species in winter wheat fields.
• To analyze aphid colony turnover at both the field and individual shoot scales.
• To identify potential vulnerabilities in aphid population dynamics for pest management.

Main Methods:

• An intensive sampling program was conducted across two winter wheat fields (120 m x 168 m).
• Aphid counts were performed on 43,050 and 45,100 occasions at 82 marked shoot locations per field.
• Colony turnover was assessed by comparing consecutive sampling occasions, categorizing them as Empty, Colonised, Extinction, or Stable.

Main Results:

• Field-scale spatial distributions of aphids generally emerged, with temporal stability varying by species and field.
• At the large (field) scale, aphid populations quickly established stability.
• At the small (shoot) scale, a high proportion of shoots remained unoccupied, exhibiting considerable colonisation and extinction events, and low stability.

Conclusions:

• Aphid populations demonstrate contrasting stability at different spatial scales within winter wheat fields.
• The high rate of colonisation and extinction at the shoot level represents a vulnerability in aphid population dynamics.
• This small-scale instability could be exploited for pest control by increasing exposure to natural enemies or imposing physiological costs on aphids.