2009 Annual Report
1a.Objectives (from AD-416)
Parkinsonia (Caesalpinioideae) was planted in Australia mainly as an ornamental and shade tree. The detrimental effects include its propensity to form dense, thorny, impenetrable thickets along drainage lines, depressions, and ephemeral wetlands. Investigations into the potential biological control began in 1983. Two insects from the Sonoran Desert Region, Rhinacloa callicrates and Mimosestes ulkei were released since 1989 and a third insect from Argentina, the seed-feeding bruchid, Penthobruchus germaini, in 1995. Additional agents are needed. Recent genetic studies indicating very old dispersal events of P. aculeata in South America, stimulated interest in survey work in this area. Previous native-range surveys conducted in Argentina and Paraguay by ARS researchers revealed the existence of two prospective geometrid moths, Eueupithecia cisplatensis (Prout) and Euacidalia sp
1b.Approach (from AD-416)
• Focus searches on warmer semi-arid areas that match target climates in Australia.
• Collect young living plants of P. aculeata for growing at the Hurlingham laboratory.
• Transport living geometrid specimen to the Hurlingham laboratory.
• Rear the specimens to adult.
• Initiate a lab colony on the living plants of P. aculeata.
• Collect data on life cycle and basic biology.
• Compile a list of related species that could be collected as young plants and grown in pots in the lab for host specificity testing.
• Collect and grow these plants.
• Conduct host specificity tests. Use no-choice test design. Attempt to obtain mating and oviposition on test plant species and P. aculeata control and record larval development.
• If direct oviposition on plants is not possible, transfer eggs onto leaves of various species and record larval development.
• Variations to host testing to be discussed with Dr Tim Heard.
• While collecting geometrids, collect, preserve and label other insect herbivores.
• If geometrids cannot be found, transfer effort into the survey of other herbivorous species.
• If any other species appear promising, attempt rearing and specificity testing within the possibility of the available resources.
• Keep herbarium specimens of plants from all sites visited.
• Keep data sheets of characteristics of sites visited.
• If appropriate, collect geometrids from neighbouring legumes when populations found on P. aculeata.
Nine exploratory trips were made in central-northern Argentina mainly for Geometrid moths. Plants were sampled mostly by visual inspection, hand collection and beating. Immature insects were held in plastic containers and provided fresh leaves until the emergence of adults.
Systematic status. Geometridae specialist in München, Germany, identified the leaf-feeding moth as Eueupithecia cisplatensis. Adult morphology. Females are bigger than males. Sexual dimorphism is also present in the antennae. Biology. Brown cylindrical eggs are usually laid individually on the leaflets. Body color of larvae changes progressively from light brown-greenish in the early instars to green-purple in the later instars mimicking P. aculeata leaf rachises and young shoots. As larvae develop, they eat most of the leaflets and parts of the rachises. Larvae that were fed bouquets of leaves of P. aculeata inside plastic jars containing wet tissue paper in the bottom spin a silk cocoon either on the jar lid or in the tissue paper. The shortest developmental period from egg to adult emergence was ca. 23 days. The duration of the stages was approximately: 6 days for eggs, 11 days for larvae, and 7 days for pupae. Natural enemies. Two species of Conura (Hymenoptera: Chalcidoidea) were obtained from cocoons. Further identification is in progress.
Laboratory host specificity of Eueupithecia cisplatensis
No-choice larval survival tests. No-choice larval survival was evaluated on 10 spp. of Fabaceae Caesalpinoideae (5 genera) and Mimosoideae (2 genera) with newly emerged larvae (F1 of field-collected specimens. Eueupithecia cisplatensis showed a strong preference for P. aculeata; the larvae exposed to other species died after 2-6 days. On the other hand, only 50% of the larvae reared on P. aculeata reached the pupal stage. Larval development will be evaluated under different conditions.
Field host specificity
On field trips, coexisting plants of P. aculeata, P. praecox and A. caven were searched for Geometridae larvae by beating. Larvae were found feeding on P. aculeata and P. praecox.
Other natural enemies
- The stem galling-midge, Neolasioptera sp. (probably a new species) (Diptera: Cecidomyiidae), was found only on Parkinsonia. Its rearing is being attempted.
- The leaf-feeding moth, Melipotis acontioides (Lepidoptera: Noctuidae) was found in several sites in northern Argentina on P. aculeata, P. praecox and Acacia caven.
- Other 3 species of Geometridae, Ennominae, moths were found on P. aculeata.
Methods used for the monitoring of this subordinate project included periodical phone calls and E-mail exchanges with CSIRO-Australia. Also, progress reports were prepared and delivered to the funding agency.