Submitted to: Environmental Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/8/2013
Publication Date: 2/1/2014
Citation: Esquivel, J.F., Medrano, E.G. 2014. Ingestion of a marked bacterial pathogen of cotton conclusively demonstrates feeding by first instar southern green stink bug (Hemiptera: Pentatomidae). Environmental Entomology. 43(1):110-115. Interpretive Summary: Southern green stink bugs are important pests of cotton and other high-value cash crops worldwide. Although it is commonly accepted that newly-hatched immatures (or nymphs) of southern green stink bugs do not feed, nymphs were observed with moving mouthparts inserted into a food source. To confirm whether nymphs feed, nymphs were fed either a sterile bean or a bean infected with a marked bacterium. Marked bacteria were detected in approximately 65% of nymphs that fed on infected beans but not in nymphs that fed on sterile beans. Further, nymphs retained the marked bacteria after molting to the second growth stage. The results clearly establish feeding by newly-hatched nymphs, and may necessitate changes to crop protection strategies against feeding and vectoring of plant pathogens by the southern green stink bug.
Technical Abstract: Long-held dogma dictates that 1st instars of Nezara viridula (L.) do not feed, yet recent observations of stylet activity within a food source suggest otherwise. As a cosmopolitan pest of cotton and other high-value cash crops, confirmation of feeding by 1st instars may ultimately influence the biology and management strategies for this pest. To clarify whether 1st instars feed, newly hatched nymphs were provided sterile green beans (control) or beans infected with a rifampicin-resistant marked bacterial pathogen of cotton. Insects were exposed to beans for 2-d and feeding was confirmed based on detection of marked bacteria internally. Normal bacterial flora was detected in all insects; however, control insects did not possess the marked bacteria. Of the 1st instars surviving on infected beans, approximately 65% possessed the marked bacteria internally. Also, the frequency of insects with marked bacteria was higher in insects collected directly from the bean surface than those that were off the bean at time of collection. Densities of innate and marked bacteria were comparable suggesting that the marked bacteria did not exclude pre-existing bacterial flora. Marked bacteria were also detected in a subset of 2nd instars, indicating marked bacteria were retained through the molting process after ingesting bacteria as 1st instars. Our findings conclusively demonstrate feeding by 1st instars and redefine the long-held perspective of non-feeding by 1st instars. These findings may necessitate changes to crop protection strategies against feeding and vectoring of plant pathogens by N. viridula.