|Cooper, William - Rodney
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2011
Publication Date: 4/4/2011
Citation: Cooper, W.R., Spurgeon, D.W. 2011. Laboratory studies of variations in feeding behaviors among Lygus hesperus Knight (Hemiptera: Miridae) of different gender and reproductive states. Environmental Entomology. 40(2):367-373.
Interpretive Summary: The western tarnished plant bug is a key cotton pest in the western United States. Feeding by plant bugs injures developing flower buds (squares) and causes them to drop from the plant. However, previous reports indicate that the level of damage caused by plant bugs is often much lower, or higher, than expected based on their numbers. This inconsistency increases the difficulty of making management decisions, and of interpreting results of studies to investigate plant bug damage. A potential explanation for these inconsistencies might be variation in feeding behavior among plant bugs of different life stages or genders. We developed methods to monitor behaviors of individual plant bugs using high-definition video. Using these methods, we compared the frequency of movement on or off of cotton squares, and the time spent feeding, by adult plant bugs of different genders and reproductive states (pre-reproductive, reproductive and mated, and reproductive and unmated). Pre-reproductive bugs fed for longer intervals and tended to stay on squares longer compared with reproductive bugs. Both unmated and mated reproductive females fed in shorter intervals compared with pre-reproductive females, but mated females probed squares with their mouthparts more times than other plant bugs. Unmated reproductive males fed for shorter intervals compared with mated males. Our results validate findings from our preliminary studies which used low-resolution video and document previously unrecognized variation in adult western tarnished plant bug behaviors. This information should prove useful to efforts to develop a better understanding of the damage caused by plant bugs.
Technical Abstract: Lygus hesperus Knight (Hemiptera: Miridae) is a key pest of cotton (Gossypium spp.) in the western United States that injures floral buds (squares) and developing fruit (bolls). Levels of lygus-induced damage to cotton can vary among lygus stages or gender, and these variations complicate interpretation of studies to elucidate lygus/cotton interactions. Variations in observed injury may reflect different behaviors among classes of lygus. We compared times allocated to feeding and trivial movement between male and female adult lygus of different reproductive states: pre-reproductive, reproductive and mated, and reproductive and unmated. Pre-reproductive adults exhibited less trivial movement and spent more time stylet-probing compared with reproductive unmated and mated adults. Mated females stylet-probed more times than other classes of lygus, while mated and unmated reproductive females exhibited more test probes (=10 s duration) than pre-reproductive females. Reproductive females probed the anther region of squares less than pre-reproductive females. Instead, reproductive females tended to stylet-probe squares below the bracts, which is also where they oviposited. Each oviposition event was preceded by a short duration stylet-probe at the oviposition location. Unmated reproductive males exhibited more test probes but fewer ingestion probes (>1 min) compared with pre-reproductive and mated males. Our results indicate a pattern in which pre-reproductive adults are less active and feed more compared with reproductive adults, but behaviors vary among reproductive adults of different genders and mating states. We propose that differences in behaviors exhibited among adult lygus are related to the different requirements imposed by mate seeking/attraction and oviposition.