Intraguild predators and the spatial distribution of a parasitoid

Area of Science:

• Ecology
• Entomology
• Agricultural Science

Background:

• Aphids are significant agricultural pests.
• Natural enemies, including parasitoids and predators, regulate aphid populations.
• Interactions between different natural enemy guilds can influence biological control efficacy.

Purpose of the Study:

• To investigate the impact of coccinellids (ladybugs) on the parasitism rates of the black bean aphid, Aphis fabae, by the parasitoid Lysiphlebus fabarum.
• To determine if aphid parasitoid behavior is influenced by the presence of coccinellids.

Main Methods:

• Field experiments monitoring aphid populations, parasitism levels, and natural enemy abundance across various host plants.
• Laboratory olfactometer experiments assessing Lysiphlebus fabarum's response to plant volatiles associated with aphids and/or coccinellids.

Main Results:

• Parasitism of Aphis fabae by Lysiphlebus fabarum was significantly lower on plants with coccinellids.
• Parasitism rates increased with aphid density on most host plants, except where high coccinellid numbers were present.
• Lysiphlebus fabarum avoided odors from plants infested with coccinellids in laboratory trials.

Conclusions:

• Coccinellid presence negatively impacts Lysiphlebus fabarum parasitism rates.
• Avoidance behavior by the parasitoid in response to coccinellids contributes to the observed inverse relationship between predator and parasitoid abundance.
• These findings highlight the complex intraguild interactions affecting biological control of aphids.