DISCOVERY, BIOLOGY AND ECOLOGY OF NATURAL ENEMIES OF INSECT PESTS OF CROP AND URBAN AND NATURAL ECOSYSTEMS
Title: Plant-mediated decisions by an herbivore affect oviposition pattern and subsequent egg parasitism
Submitted to: Arthropod-Plant Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 11, 2011
Publication Date: July 12, 2012
Citation: Williams Iii, L.H., Zhu, Y., Snodgrass, G.L., Manrique, V. 2012. Plant-mediated decisions by an herbivore affect oviposition pattern and subsequent egg parasitism. Arthropod-Plant Interactions. 6:159-169. DOI 10.1007/s11829-011-9165-0.
Interpretive Summary: Plant bugs are serious pests of many crops throughout the United States. However, weeds are also important to plant bugs, because weeds serve as hosts on which the bugs feed and reproduce in seasons when crops are not available. Thus, weeds serve as a bridge from one crop growing season to another for the plant bugs. Beneficial insects are useful in killing plant bugs on weeds and thereby reducing the numbers of plant bugs that disperse to and damage crops. Therefore, understanding the effect of beneficial insects on plant bugs inhabiting weeds has important implications for plant bug control. We conducted experiments to characterize the spatial pattern of plant bug egg distribution on several weeds and crops favored by plant bugs, and the subsequent performance of a beneficial insect that attacks plant bug eggs. Plant bugs laid the majority of their eggs on flower buds, fruit, and other reproductive structures. On several plant hosts the eggs were laid in such a way that they were hidden from the beneficial insect, and thus escaped attack. Our results suggest that certain weeds provide plant bug eggs a refuge from attack, thus limiting the level of control by the beneficial insect. These findings help identify weed management strategies important for improving plant bug control.
Natural enemies are important mortality factors for herbivores and thus may influence herbivore population dynamics. In response to natural enemy pressure, herbivores can alter life history decisions, such as oviposition behavior, so that offspring are protected from natural enemies. One such strategy is to deposit eggs into structures where vulnerability to natural enemies is reduced or eliminated, i.e., use enemy-free space. The plant bug, Lygus lineolaris (Palisot de Beauvois), is native to North America and has a broad host range (>350 plant species), including crops. This bug’s eggs are attacked by a native parasitoid, Anaphes iole Girault, and parasitism levels vary greatly among host plants. Non-crop weedy hosts are critical to contemporary L. lineolaris life history, because they serve as an ecological bridge from one crop growing season to the next. We investigated the egg distribution pattern of L. lineolaris on 11 host plants (nine weeds and two crops), and parasitism by A. iole, to determine whether oviposition choices by L. lineolaris females protect their eggs from parasitism. Our results indicate that the reproductive structures of several host plants provide a refuge from parasitism for most L. lineolaris eggs. Also, overall parasitism levels were greater on exotic host plants compared to native plants. Oviposition site choice by female bugs appears to be a selective strategy to take advantage of enemy-free space.