Bulletin 25 2010 - BSES

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10 Treatment QCrOps / peTer sAMsON, keiTh ChANDLer, NADer sALLAM CANeGruB MANAGeMeNT AND NeW fArMiNG sysTeMs iN This ArTiCLe Bses priNCipAL reseArCher peTer sAMsON BAseD AT MACkAy, seNiOr reseArCher keiTh ChANDLer BAseD AT BuNDABerG AND reseArCher NADer sALLAM BAseD AT GOrDONvALe DisCuss The iMpOrTANT TOpiC Of CANeGruB CONTrOL iN The LiGhT Of NeWLy iNTrODuCeD AGrONOMiC prACTiCes. Many cane growers are adopting one or more of the farming techniques developed over the past decade that involve legume rotations, controlled-traffic and reduced tillage. Canegrub control is critical to successful sugarcane farming in Australia. It is vital that with these changes to agronomic systems, growers maintain good control of these pests (as well as other pests, diseases and weeds). ‘New farming systems’ should encompass not only sustainable agronomic practices but also sustainable pest management with more precisely targeted pesticide application than has been the rule. Monitoring to decide when and where to treat for canegrub control should be part of any new system. In this article we consider the influence of different agronomic practices on the risk of canegrub infestations, and outline an integrated approach to monitoring and managing them. We draw heavily on recent research on canegrub management in new farming systems funded in part by the Sugar Research and Development Corporation. More detail will be available in an upcoming booklet. GeNerAL priNCipLes Of CANeGruB MANAGeMeNT These principles should guide sustainable pest management in sugarcane: • When adopting sustainable farming systems, avoid practices that increase grub numbers or exaggerate their effect on the crop • Adopt pest monitoring systems that allow you to: - apply canegrub control measures when justified by risk and by cost and expected benefits - avoid applying insecticides when not needed – thus saving money by avoiding unnecessary treatment, minimising the risk of environmental contamination, and delaying development of pest resistance to insecticides and accelerated breakdown in soil iNfLueNCe Of LeGuMe rOTATiONs Canegrubs sometimes turn up in soybean crops that are grown in rotation with sugarcane, and they will feed on soybean roots. However, legumes do not create canegrub problems. There are big benefits from legume rotations, so growers should grow legumes and monitor and manage the risks from canegrubs as set out below. Soybean crops may harbour greyback and southern 1-year canegrubs (1-year species) and Childers and negatoria canegrubs (2-year species). for the 2-year species, canegrubs in soybean crops may include both newly recruited grubs plus grubs surviving into their second year. Nevertheless, actively growing crops of sugarcane are still the most attractive places for cane beetles to fly to and lay eggs – see Table 1. The main indicator determining risk of canegrub attack is the presence of grubs in the previous cane crop. TABlE 1 | Comparison of numbers of greyback canegrubs in plots with different fallows; many more grubs were found in plots with ratooning cane than in fallow or soybean plots. Cultivated fallow Grubs / 8 holes 0.0 Cultivated + soybean 0.3 Sprayout fallow 0.8 Sprayout + soybean 1.0 Ratooning cane 20.3 Soybean crops are an opportunity to monitor fields for canegrubs, as the fields are easily accessible and any light infestations can then easily be managed in the following cane crop. Cane volunteers seem to attract egg-laying beetles, so monitor those first for any sign of grubs. legume rotations may assist canegrub management by favouring the occurrence of natural diseases of canegrubs. A variety of disease organisms that live in soil can give some natural control of the grubs. The two most important of these are the fungus Metarhizium (the active component of the biocontrol product BioCane) and the protozoan Adelina, but other grub diseases such as milky disease also occur. Significantly more greyback canegrubs were infected with the pathogen Adelina in ratoon fields in far northern Queensland (where Adelina is abundant) when there had been a soybean crop prior to planting (see Table 2).
IMAGE 1 | Spores of the protozoan disease Adelina in the haemolymph (‘blood’) of a greyback canegrub (CSIRO photograph). TABlE 2 | Percentage of greyback canegrubs infected with the grubdisease Adelina in a survey of canefields with or without a soybean rotation before planting (numbers in brackets are number of fields surveyed). Region % with different rotations Central Herbert Innisfail - Tully Mulgrave Combined Soybeans No rotation 5 (4) 26 (8) 14 (2) 24 (9) 21 (23) 2 (17) 11 (19) 16 (17) 18 (<strong>25</strong>) 12 (78) However, similar results were not seen in central Queensland where the disease is very uncommon. Changes to farming systems in districts where pathogens are currently rare are unlikely to bring about rapid change in grub disease status in those fields. CONTrOLLeD-TrAffiC AND reDuCeD TiLLAGe Tillage, even if very intensive, will not eliminate existing canegrub infestations or prevent new ones. for example, canegrubs were sampled in soybeans that had either been (i) directdrilled into cane that had been sprayed out with glyphosate or planted after cane stools had been disced out; or (ii) planted after full cultivation (eg plough, disc and rotary hoe). Prior intensive cultivation did not eliminate most species of canegrubs from fields – see Table 3 below. TABlE 3 | Comparison of numbers of canegrubs in (i) soybean crops that were either direct-drilled or planted after discing or (ii) planted after full cultivation. Canegrub Average grubs per hole (no. fields sampled in brackets) Greyback Southern 1-year Childers: 1st yr grubs 2nd yr grubs Directdrilled or disced 0.9 (3) 0.6 (1) 0.9 (6) 0.7 (6) Reduced tillage also seems to benefit canegrub control by preserving grub diseases in the soil. In far northern Queensland, infections of greyback canegrubs with the common disease IMAGE 3 | Greyback canegrub infected and killed by Metarhizium fungus (CSIRO photograph). Full cultivation 0.0 (4) 0.4 (3) 1.1 (9) 0.7 (9) IMAGE 2 | Canegrub-damaged sugarcane. Metarhizium were significantly greater in ratoon fields where fields had been prepared for planting with zonal tillage – cultivation of only the row and not the interspace – rather than conventional (full) tillage – see Table 4. TABlE 4 | Percentage of greyback canegrubs killed by the disease Metarhizium in canefields prepared for planting by either zonal or conventional tillage. District Average % infected (no. fields in brackets) Innisfail - Tully Mulgrave Combined Zonal Conventional 22 (4) 11 (6) 15 (10) 6 (14) 6 (28) 6 (42) IMAGE 4 | Cane stool damaged by greyback canegrub. p 1 1 i s s u e 2 5
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Page 3 and 4: QCrOps / BArry sALTer evALuATiON Of
Page 5 and 6: TABlE 4 | Cane (TCH) and sugar (TSH
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Page 9: MAryBOrOuGh CANe prODuCTiviTy servi
Page 13 and 14: MONiTOriNG Childers canegrub life c
Page 15 and 16: 7 risk Of iNTrODuCTiON The movement
Page 17 and 18: Grower Area of cane (ha) Soil type
Page 19 and 20: Bses LiMiTeD / eve MCDONALD past iN
Page 21 and 22: Heather Boreland, Head of the Scien
Page 23 and 24: 1 5 A widely used saying in the ind
Page 25 and 26: for cane borers that could spread t
Page 27 and 28: Bses LiMiTeD / DATe CLAiMers 2010 B

Bulletin 25 2010 - BSES

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