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Pests > Pest Management > Chemical control > Synthetic pesticides > Insecticides > Target & Karate, Oribius weevils, PNG
January 2006. A useful report on the NARI/FPDC/QUT implemented, ACIAR funded, project in Papua New Guinea that appeared in the National Monday 23 January 2006.
Keeping weevils away: Highlands farmers can now control the destructive Oribius weevil.
Oribius weevils are small beetles. They are regarded as important insect pests and are common throughout Papua New Guinea. The weevils feed on many different plants including agricultural crops, ranging from leafy vegetables and fruits to introduced orchard trees and field crops such as coffee.
These flightless weevils can cause significant loss in crop growth, decline in yield, downgrading of crop marketability and, in severe cases, increased tree and seedling mortality.
Damage has been recorded on some important crops like avocado, capsicum, citrus, cabbage, strawberry, and other plants.
The adults, measuring 4-7mm long, are the crop damaging stage. These dark brown, dark grey or black Oribius adults feed on leaves, soft shoots, green stems, flower buds and developing fruits, causing extensive damage. But now there is a management package recommended by the National Agricultural Research Institute (NARI) to control these little known pests. The technology was released to the PNG farming community during a field day in Aiyura, Eastern Highlands province late last year.
Highland farmers who feel the impact of Oribius damage to their agricultural crops can adopt the technology and improve their food production. The recommendations, documented in various publications, follow from a collaborative research study on the impact and management of the Oribius weevils in PNG.
NARI, the Fresh Produce Development Agency and the Queensland University of Technology, Australia, conducted the four-year research project in the Highlands with much of the work done in EHP.
NARI Chief Scientist Dr Alan Quartermain said the release package contains recommendations on type of insecticides, dose rates and timing of application both in terms of time of year and time of day.
Dr Quartermain said elimination of preferred weed host plants, eg thickhead, and the use of non-preferred plants such as spring onion, carrot, cassava and highlands pitpit in intercropping or border planting can reduce Oribius damage and colonisation levels.
Although these beetles are dominant throughout the year, they are highest in numbers between December and June and farmers should be watchful for attacks on important crops.
The study, funded by the Australian Centre for International Agricultural Research, was concentrated on managing the two dominant pest species of the region – Oribius inimicus Marshall and O destructor Marshall.
A series of laboratory and field trials were conducted to identify environmentally sound and economically viable plant protection technologies which will increase crop yield and improve farmer income.
This biological investigation confirmed the importance of this group of weevils as a most important pest of a range of food crops in Eastern Highlands.
The levels of potential crop loss for five important crops – avocado, cabbage, capsicum, citrus and strawberry – have been documented. Two most commonly used and effective insecticides, Karate and Target, were recommended to control the weevils.
Farmers can directly spray only a quarter (1/4) or half (1/2) of the manufacturers¹ recommended rates on the insects.
Spraying should be done in the morning hours and mid-afternoon on sunny days for best results, since beetles will be feeding on the crops at these times.According to a simple cost benefit analysis using average market values for capsicum (K3.52) and average store costs of insecticides (Karate K29.03/L, Target K72.30/200ml, Wetting agent K16.00/5L) for 2004-2005, treatments to control Oribius weevils were highly profitable with 1/4 strength Karate control yielding a K66.40 increase in return over no control.
These results show that costs associated with the control strategy are easily compensated for by the significant increase in yield.
Project leader and expert from Queensland University of Technology, Dr Anthony Clarke, said the Australian government funded research was carried out by PNG agricultural research scientists based on the needs of local farmers regarding the attacks on agricultural crops by Oribius.
He said the findings and recommendations are now available with NARI for farmers to obtain and implement to improve their food production and wellbeing in the community.
The exact number of different Oribius species is unknown, but at least 50 are thought to exist of which seven are pests of PNG agriculture. They are flightless and walk onto their host plants.
More information on the weevils, their impact and management control practices are available from NARI for public knowledge.