Research and industry stakeholders met with project staff to prioritise target crops and endorse the project at a start-up meeting at Aiyura in August 2002, and fieldwork commenced in October 2002.
500 Oribius species have so far been collected or recognised in collections, and a synopsis of the genus is being prepared. This work is being undertaken through collaborative research between PNG and Queensland Museum staff. Five pest species (O. destructor, O. inimicus, O. cruciatus, O. cinereus and O. improvidus) have been confirmed, while two other species are recognised but specific identifications are yet to be confirmed. Three related genera, causing similar damage to Oribius have also been recognised: Aulacophrys, Apirocalus and Idiopsodes. Identification guidelines for the key pest species have been sent to the field based researchers.
The immature (egg and larval) stages of Oribius have been identified and collected from the field for the first time. This allows more targeted efforts to understand the life-cycle of the insect and habitat preferences in the field.
Field-based impact trials have been designed and established to quantify Oribius damage on citrus, coffee, avocado, strawberry, capsicum and cabbage. An agricultural economist has been involved in these trials from their initiation, to ensure maximum inferences can be drawn about weevil impacts on the local agricultural community.

The four objectives of the Oribius project are to: (i) get a better understanding of the biological and economic impacts caused by the pests; (ii) gain an understanding of the ecology pertinent to control; (iii) trial different insecticides for their management; and (iv) better understand the taxonomy of the genus. Substantial progress has been made in all four areas leading to an enhanced understanding of these pests.

Impacts
Excluding adult Oribius weevils has been demonstrated to increase marketable fruit on capsicum, strawberries and avocado by 200-220%. This dramatic increase is despite the fact that exclusion treatments were only approximately 50% effective in most cases (ie the numbers of weevils on treatment plants were reduced by only half of those on unprotected controls). In citrus, highly susceptible to Oribius weevil, fruit yield on protected plants was 1800% higher than that on unprotected plants: unprotected citrus are killed by repeated leaf and shoot feeding of Oribius weevils and produce essentially no yield. Of the crops tested, only cabbage did not suffer Oribius damage, with insects rarely being present on this crop. In structured surveys of plants in the Aiyura Valley, Oribius were also shown to be common on pepino, sunflower, guava, choko tips, peanuts and corn and are almost certainly pestiferous on these crops, although formal impact assessments have not been carried out. An economic evaluation of the impact of Oribius on Highlands agriculture is underway, with market surveys having been completed to assess the amount and value of particular crops grown and subsequently taken to market.

Ecology
Basic understanding of Oribius ecology is slowly being gathered. Adults of O. destructor and O. inimicus can be collected from a wide variety of plants in the field, but host usage in the field is not uniform with some plants highly preferred and other used rarely. Host usage by O. destructor and O. inimicus is not identical, although many hosts are shared. In a structured host survey around the Aiyura Valley, 20% of all O. inimicus were collected from pepino (Solanum muricatum) and 18% of O. destructor from poinsettia (Euphorbia pulcherrima), despite these species each constituting only 4% of plants sampled (total number of weevils collected = 1270). In stark contrast, just over 2% of either Oribius species were collected from combined samples from slender amaranth, milkweed, sowthistle, slender knotweed, black nightshade and wandering jew, despite these plants representing 24% of all plants surveyed. Oribius larvae have been demonstrated to be root feeders and, at least for O. inimicus, larvae grow well on the roots of a plant (thickhead, Crassocephalum crepidioides) from which adults are frequently collected. The relationship between adult and larval usage of host plants is being further explored. Adults appear to move regularly on and off host plants, with recapture rates of marked beetles low and re-infestation of previously sprayed plants rapid. Ecological research is focusing on understanding aspects of the weevils' biology which may be utilized in management.

Insecticides
Laboratory trials have assessed the efficacy of Karate (active ingredient lambda-cyhalothrin), Target (active ingredient permethrin), orthene, malathion and chlorphyrifos. All chemicals are currently registered for agricultural use in PNG and are available to growers off-the-shelve. As topical applications (ie sprayed directly on the insects), Karate, Target and Chlorphyrifos gave good knockdown rates within 5-15 minutes, however, Karate and Target produced better kill rates than Chlorphyrifos when the insecticide was applied to the substrate (filter paper) or host-plant foliage and are thus more likely to give better results in the field. Topical applications of Karate, Target and Chlorphyrifos at manufacturer's recommended dosage gave kill rates not significantly worse than full strength applications.

Taxonomy
The taxonomic status of the pest species of Oribius in PNG has been clarified. There are seven such species: O. cinereus Marshall, O. cruciatus (Faust), O. destructor Marshall, O. improvidus Marshall, O. inimicus Marshall, Oribius sp. near leucopleurus (Faust), and Oribius sp.1. Each of these has been illustrated and described in a technical document which is currently being worked into a formal publication. Both paper-based and computer-based (Lucid) keys have been completed for these species. Due to confusion in the taxonomic literature, the exact number of species in the genus remains unclear but probably exceeds fifty. The distribution of the genus is confirmed as being restricted to the Island of New Guinea, some of its small off-shore islands, the Torres Strait Islands and the far northern tip (Cape York) of mainland Australia.

Biological and Economic Impacts
An extensive farmer-based crop impact survey was undertaken in Eastern Highlands Province, with leaf and fruit damage estimates obtained from individual growers throughout the region. Twenty-four of the most commonly grown crops (additional to those for which we have existing experimental data) were included in the survey. Surveys were based on a relative damage scale (High, Medium and Low). Farmers recognised some level of oribius damage on all but three of the crops surveyed. However, relatively few farmers (generally <15% for any particular crop) scored oribius damage as high. While we don't expect all crops to be attacked at a consistently high level, we suspect, based on our experimental studies, that farmers underestimate the impact of oribius on crop yield. For example, cabbage was originally included in our earlier impact trials simply because of its regional importance, but no local stakeholders considered it to be subject to oribius attack. Nevertheless, our formal trials subsequently showed a 30% improvement in yield when the crops were protected. This issue of assessing real crop impact should be regarded as a priority for further research and extension programs.

Ecology
Preliminary studies on the use of biological barriers and intercropping techniques yielded mixed results. Spring onion and highland pit pit barriers reduced the numbers of Oribius invading and feeding on crop. Spring onion intercropping also reduced damage and colonisation levels significantly.

Insecticides
Field validation studies were undertaken for the two most effective insecticides identified in laboratory trials (Karate and Target). Twenty-four trial plots with 20 capsicum plants in each were constructed so that each insecticide had three dose plots, three dose plots, three full dose plots and three control plots. Plots were sprayed on a need basis, with all fruit collected and weighed progressively throughout the season.

In the field, Karate gave significantly better control than Target. Further, recommended manufacturers' rate gave as efficient control as spraying at the full rate for both insecticides. A simple cost benefit analysis was undertaken on insecticide control techniques. Costings are based on average market value of capsicum for 2004-2005 (K3.52) and average store costs of insecticides (Karate K29.03/L, Target K72.30/200ml, Wetting agent - Holimpas K16.00/5L). Results of the cost-benefit analysis showed that treatments to control oribius were highly profitable, with strength Karate control yielding a K66.40 increase in return over not controlling oribius (Table 1).

Overall results of spray trails suggest that use of either Karate or Target at manufacturer's concentration will significantly increase yield. The lower cost of Karate and it extra efficacy in the field should make it the chemical of first choice. Costs associated with the control strategy are easily compensated for by the significant increase in yield.

Table 1: Cost benefit analysis for control of Oribius using variable insecticide application concentrations for 60 capsicum plants. Profit based on average market value and total production for each treatment.

KARATE
Treatment

ControlFull
Cost (treatment)
0.000.160.230.38
Market Value (K/kg)
3.523.523.523.52
Productivity (Kg)
23.742.639.039.7
Profit (Kina)
83.42149.79137.05139.36

TARGET

Cost (treatment)
03.77.3114.54
Market Value (K/kg)
3.523.523.523.52
Productivity (Kg)
16.724.622.225.0
Profit (Kina)
58.7882.8970.8373.46