|Cooper, William - Rodney
Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/18/2012
Publication Date: 7/25/2013
Citation: Spurgeon, D.W., Cooper, W.R. 2013. Sweepnet captures of Lygus hesperus (Hemiptera:Miridae) adult genders and age-classes in cotton. Journal of Entomological Science. 48(3):195-205.
Interpretive Summary: Management of the western tarnished plant bug (lygus bug) in cotton usually relies on information provided by sweepnet samples. Laboratory and greenhouse studies have shown that ability of adult lygus to injure cotton varies with their age and gender. It is not known whether effectiveness of the sweepnet is the same for all lygus age classes or for both genders. We used marked and released insects to evaluate the ability of the sweepnet to collect young (pre-reproductive) and older (reproductive) lygus bugs of both genders in both Pima and Upland cotton. Effectiveness of the sweepnet declined for all classes of lygus bug as plant size and development increased. In Pima cotton, the sweepnet was least effective for sampling younger female lygus bugs, and most effective for collecting older males. In Upland cotton, effectiveness of the sweepnet was similar for all groups of lygus bug. We suggest the influence of lygus bug adult age and gender observed in Pima cotton corresponds to a preference for younger adults to feed in plant terminals substantially shielded by foliage. In comparison, the more open structure of the Upland terminal minimized the effects of these feeding preferences. Dissection of native lygus bugs, collected concurrently with the marked bugs, indicated the natural population is dominated by older, reproductively mature adults. Therefore, future sampling studies using marked and released insects should focus on factors influencing effectiveness of the sweepnet for collecting reproductively mature adults.
Technical Abstract: Management of the western tarnished plant bug, Lygus hesperus Knight, in cotton usually relies on population estimates obtained using the sweepnet. Recent studies indicated adult L. hesperus gender and physiological age influence feeding behavior, within-plant distribution, and injury to cotton. Whether these differences in behavior also influence capture by the sweepnet is not known. We evaluated the sweepnet for sampling L. hesperus adults of known gender and age class in Pima and Acala Upland cotton. Adults of four classes (females, prereproductive or reproductive; males, prereproductive or reproductive) marked with fingernail polish to prevent flight were released into assigned sample rows. Captures of marked adults declined seasonally in all experiments. In Pima cotton, the sweepnet was least effective for sampling prereproductive female L. hesperus, and most effective for collecting reproductive males. Captures of reproductive females and prereproductive males were intermediate. We suggest the influence of adult gender and age class on sweepnet captures in Pima cotton corresponds to a propensity for prereproductive adults to reside within plant terminals substantially shielded by foliage. Similar differences in Upland cotton were not observed, probably because the comparatively open structure of the Upland terminal minimized the effects of gender and age class on collection efficiency. Finally, dissection of native L. hesperus indicated an age structure dominated by reproductive maturity. Therefore, future mark-release-recapture studies of factors influencing sweepnet sampling for L. hesperus adults in cotton may maximize relevance by focusing on reproductively mature adults.