RESEARCH & EVENTS
Almond carpophilus beetle : Progress towards ‘ Attract and Kill ’
By David Madge , Cathy Taylor and Paul Cunningham ( Agriculture Victoria ) for the Almond IPM Team .
Introduction SINCE 2014 , Australia ’ s almond crops have suffered kernel damage by Carpophilus truncatus , the almond carpophilus beetle . This 2-3mm long pest infests nuts at hull split , and subsequent feeding by adults and larvae make the kernels unmarketable . In orchards , populations of this beetle are supported by crop residues left after harvest . Effective crop removal is therefore an important management tool , as it limits the pest ’ s reproductive potential by minimising the available food resource . Mass attract and kill ( A & K ) is a pest management strategy that has promise for controlling the beetle in almonds alongside good crop hygiene . For A & K , traps containing pest-specific lures are distributed throughout the crop and kill enough insects to reduce pest populations and damage levels . A & K is used successfully to protect stone fruit crops from several Carpophilus species . These commercially available traps are baited with a synthetic two-part lure : a blend of pheromones that the beetles produce to encourage aggregation , and a synergistic ‘ co-attractant ’ based on yeast odours that attract the beetles . Carpophilus truncatus is a different species to those attacking stone fruits , and the stone fruit lure does not work effectively on this pest . After several years of world-leading research in chemical ecology , Agriculture Victoria has identified , isolated , synthesised , and field-validated a new lure based on the C . truncatus pheromone . The research was funded by Agriculture Victoria and Hort Innovation ( Almond Levy Fund ), through Project AL16009 ‘ An Integrated Pest Management ( IPM ) program for the Australian almond industry ’ and its successor , Project AL22003 . This article describes the development of A & K for C . truncatus using the new lure . Development of the lure itself will be covered in a later article .
Field-testing the potential for A & K Traps containing the new lure have captured large numbers of C . truncatus in almond orchards and will be an excellent monitoring tool to inform pest management decisions . To be useful for mass A & K , traps placed throughout the orchard must be capable of reducing the beetle population sufficiently to be cost-effective at reducing kernel damage . Knowing how many traps per hectare are needed to achieve this is essential . Agriculture Victoria began to determine the optimal trap spacing through a replicated field trial conducted during 2022 / 23 . That trial , in a commercial almond orchard , tested the suitability of four trap density treatments for A & K of the beetle : 2.6 , 4.9 , 12.4 and 49.4 traps / ha , equating to approximately 8 , 6 , 4 and 2 row spacings respectively .
Figure 1 . Mean catch of C . truncatus per trap . Insert indicates compass direction of traps relative to the central trap ( dark blue , marked with an X ). Columns with different labels are significantly different within trapping density . A significantly lower catch in central traps ( X ) indicates overlapping of the radius of attraction of the traps .
The traps were arranged in square plots of nine traps ( 3 rows of 3 traps ). The trial sought to determine at what distance the traps interacted competitively ( i . e . were close enough that their “ radius of attraction ” overlapped ), as evidenced by reduced beetle catches in the centre traps . A reasonable level of competition is considered necessary for effective A & K of insect pests to maximise total catch across all traps . For 12 weeks , 144 traps were maintained across all treatments , and 864 trap samples collected . These samples averaged 98.4 % C . truncatus ( showing the high specificity of the new lure ), with a total catch of over 980,000 beetles . Competition between traps was detected at the three higher trapping densities , with the strongest competition seen at the highest density , as expected ( Figure 1 ).
Field assessment of A & K to reduce kernel damage Based on a full analysis of this data , a highlyconservative trap spacing of three rows ( approximately 22m ) was considered appropriate for a field test of A & K in almonds . While this is a high trapping density ( and unlikely to be practical at scale ), our purpose was to obtain proof of concept for mass A & K using the trap , i . e . that it can effectively reduce kernel damage . For this , a replicated field trial was conducted during 2023 / 24 . Ten experimental plots of 5.7ha were selected across a commercial orchard , after presence of the beetle throughout each plot was confirmed through inspections of nuts on the orchard floor . The 10 plots were paired for analysis purposes , based on having similar beetle damage levels at the 2023 harvest . One plot from each pair had 94 traps installed ( 16.6 traps / ha ), the other plot was used as a trap-free control . Continued page 28
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