Predation on immature parasitoids and its impact on aphid suppression

Area of Science:

• Agricultural Entomology
• Biological Control
• Ecology

Background:

• Intraguild predation occurs when predators consume prey that are also attacked by other natural enemies.
• Introducing predators to existing host-parasitoid systems can either enhance or disrupt biological control.
• The cotton aphid (Aphis gossypii) is a significant agricultural pest.

Purpose of the Study:

• To evaluate the impact of introducing the convergent ladybird beetle (Hippodamia convergens) on the biological control of cotton aphids by the parasitoid (Lysiphlebus testaceipes).
• To assess the effects of intraguild predation in an early-season cotton agroecosystem.

Main Methods:

• Field experiment evaluating the combined effects of H. convergens and L. testaceipes on A. gossypii populations.
• Quantification of predation rates on aphid mummies and host aphids.
• Measurement of aphid population suppression, mummification rates, and plant biomass.

Main Results:

• Hippodamia convergens intensely preyed on immature parasitoids (98-100% of mummies consumed).
• Despite high intraguild predation, the combination of H. convergens and L. testaceipes resulted in the greatest aphid population suppression.
• H. convergens showed a partial preference for unparasitized aphids over aphid mummies.

Conclusions:

• Predators with a partial preference for unparasitized hosts can improve herbivore suppression, even with high intraguild predation.
• Intraguild predation did not disrupt cotton aphid biological control in this early-season cotton agroecosystem.
• The combined use of predators and parasitoids can be an effective strategy for managing agricultural pests.