Evaluation of egg parasitoid Hadronotus pennsylvanicus as a prospective biocontrol agent of the leaffooted bug Leptoglossus zonatus

Abstract

The western leaffooted bug, Leptoglossus zonatus (Dallas) (Heteroptera: Coreidae), is a key pest of almonds and pistachios in the USA. With limited monitoring strategies and no economic threshold developed, the use of broad-spectrum insecticides remains the primary control tactic for L. zonatus. In pursuit of more sustainable management options, experiments were carried out to assess the biocontrol potential of the egg parasitoid Hadronotus pennsylvanicus (Ashmead) (Hymenoptera: Scelionidae) against L. zonatus. Biological and demographical attributes of H. pennsylvanicus were evaluated under controlled laboratory conditions. Mated females lived on average 116 days. However, female longevity declined by 74% when provided with host eggs, and by 97% when deprived of a suitable diet. Females produced an average 39.70 offspring, with peak fecundity observed within the first week of their lifespan. The total progeny was on average 92.75% female. Non-reproductive host mortality accounted for > 52% of the total egg mortality observed within the first two weeks, and represented the majority of total host egg mortality thereafter. Age of host eggs did not influence parasitism rates. Under laboratory conditions, H. pennsylvanicus exhibits suitable demographic and reproductive traits as a candidate biocontrol agent of L. zonatus. Further research is needed to determine how to best manipulate and enhance H. pennsylvanicus populations to promote biocontrol of L. zonatus under field conditions.

Food deprivation alters reproductive performance of biocontrol agent Hadronotus pennsylvanicus

“…Hadronotus (= Gryon 17 ) pennsylvanicus (Ashmead) (Hymenoptera: Scelionidae) is a generalist synovigenic egg parasitoid, known to attack the leaffooted plant bug, Leptoglossus zonatus (Dallas) (Heteroptera: Coreidae) 18 along with several other coreid pests including L. phyllopus (L.) 19 , L. australis Fabricius 20 , L. occidentalis Heidemann 21 – 23 , Anasa tristis (DeGeer) 24 , 25 , and A. armigera Say 26 . In California, U.S.A., L. zonatus has become an increasingly problematic pest of almonds ( Prunus dulcis L.) and pistachios ( Pistacia vera L.) 27 – 29 .…”

“…Feeding from L. zonatus has the potential to cause significant damage to these nut crops and can facilitate such fungal contaminations as stigmatomycosis and Botryosphaeria, all of which lowers crop yield and quality 30 – 36 . Under laboratory conditions, H. pennsylvanicus exhibits suitable demographic and reproductive traits suggesting its potential use as a biocontrol agent for L. zonatus 18 . However, access to a carbohydrate-rich diet is likely critical to maximize lifetime fitness of H. pennsylvanicus .…”

“…However, access to a carbohydrate-rich diet is likely critical to maximize lifetime fitness of H. pennsylvanicus . Previous studies demonstrated that females deprived of a honey-water diet died shortly after eclosion, resulting in significantly fewer offspring over their short lifetime 18 , 37 – 39 . Furthermore, egg limitation appears to be a constraint on lifetime fecundity of female H. pennsylvanicus 18 , 26 , 38 .…”

“…Previous studies demonstrated that females deprived of a honey-water diet died shortly after eclosion, resulting in significantly fewer offspring over their short lifetime 18 , 37 – 39 . Furthermore, egg limitation appears to be a constraint on lifetime fecundity of female H. pennsylvanicus 18 , 26 , 38 . Under continuous reproductive opportunity, the proportion of parasitoid-induced aborted eggs increased with female age, ultimately accounting for the majority of total host egg mortality 18 .…”

“…Furthermore, egg limitation appears to be a constraint on lifetime fecundity of female H. pennsylvanicus 18 , 26 , 38 . Under continuous reproductive opportunity, the proportion of parasitoid-induced aborted eggs increased with female age, ultimately accounting for the majority of total host egg mortality 18 . Since H. pennsylvanicus likely does not feed on their host 40 , such non-reproductive host mortality may facilitate additional pest control in the absence of mature eggs.…”