Attractants for ACP trapping technology: Challenges, status, and opportunities

Authors: Patt, Joseph - Joe; SETAMOU, MAMMOUDOU - TEXAS A&M UNIVERSITY

Submitted to: International Research Conference on Huanglongbing
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2014
Publication Date: 1/2/2015
Citation: Patt, J.M., Setamou, M. 2015. Attractants for ACP trapping technology: Challenges, status, and opportunities. International Research Conference on Huanglongbing. https:escholarship.org/uc/item/9jw2w985.

Interpretive Summary: The Asian citrus psyllid is a tiny insect that transmits the bacterium that is thought to be responsible for causing Citrus Greening disease, otherwise known as Huanglongbing. There is currently no cure for Citrus Greening, which is either fatal or permanently debilitating to all species of commercial citrus. The psyllid’s searching behavior for citrus trees is complex and sophisticated. It can be influenced by citrus tree species, the tree’s growth stage, the tree’s health condition, and the psyllid’s gender and mating status. The psyllid’s behavior is also influenced by the citrus greening disease’s influence on the tree’s aroma. Asian citrus psyllid relies on leaf color to locate citrus trees, but evidence suggests that leaf aromas may influence the psyllid’s response to leaf colors. Scent lures could potentially enhance psyllid response to the bright yellow and green background colors of the sticky traps used in Asian citrus psyllid (ACP) monitoring programs. However, because host foliage aromas are complex, dynamic, and species-specific, developing an effective scent lure is challenging. Here we explore some aspects of lure composition and deployment which may increase trap yield: (1) Scent lure efficacy may be influenced by setting. In residential areas, a generalized scent lure comprised of leaf aroma compounds common to several host species may work well, while a scent lure used in groves might need to mimic the scent of the grove trees to be effective. Alternatively, a lure that mimics ‘super hosts’, plants that are highly attractive to the psyllid such as orange jasmine, may work well in a variety of situations. (2) Volatiles that signal the presence of young leaves may be important components in scent lures. Growing shoots are essential for psyllid reproduction. Signature odors might include leaf waxes, ammonia, methanol, and carbon dioxide, all of which are emitted during leaf expansion. These compounds may synergize the psyllid’s response to the essential oil aromas emitted by scent glands present in the leaves. A better understanding of these factors could lead to the development of scent lures that are consistently effective in a variety of application situations. Better monitoring tools would especially be useful where psyllid population densities are low or for tracking psyllid movement patterns.

Technical Abstract: Psyllid host searching behavior is complex and sophisticated. It can be influenced by host species, growth stage, and physiological condition, psyllid gender and mating status, behavioral plasticity, usurpation by phytopathogens of host aromas, and psyllid-induced emission of foliar volatiles. Asian citrus psyllid (ACP) relies on visual cues to locate its host plants, but evidence suggests that olfactory cues mediate visual response. Scent lures could potentially enhance psyllid response to the bright yellow and green background colors of the sticky traps used in ACP monitoring programs. However, because host foliage aromas are complex, dynamic, and species-specific, developing an effective scent lure is challenging. Here we explore some aspects of lure composition and deployment which may increase trap yield: (1) Scent lure efficacy may be influenced by setting. In residential areas, a generalized scent lure comprised of volatiles common to several host species may work well, while a scent lure used in groves might need to mimic the scent of the grove trees to be effective. Alternatively, a lure that mimics ‘super hosts’, such as orange jasmine, may work well in a variety of situations. (2) Volatiles that signal the presence of flush may be important components in scent lures. Flushing shoots are essential for ACP reproduction. Signature odors might include cuticular hydrocarbons, ammonia, methanol, and carbon dioxide, all of which are emitted during leaf expansion. These compounds may synergize ACP response to terpenes emitted by foliar scent glands. (3) Sesquiterpenes may be important signal compounds. These terpenes are prevalent in the aromas of ‘super hosts’ but most are commercially unobtainable; little is known about their effect on psyllid attraction. A better understanding of these factors could lead to the development of scent lures that are consistently effective in a variety of application situations. Better monitoring tools would especially be useful where ACP population densities are low or for tracking psyllid movement patterns.