DURING the past few seasons there have been increased reports of establishment issues without an immediately obvious cause. Closer investigations have shown that

while the responsible factors vary from field to field, an often overlooked aspect has been the presence of soil pests such as wireworms and earwigs. The millipede-like pest symphyla has also been implicated as a causal factor in some fields although the actual pest status of this organism is unclear.

Conversations with people managing affected fields indicate

uncertainty surrounding the apparent variability between fields in terms of crop damage and seeming pest presence. This article will provide a brief overview of type of pests that can cause crop establishment difficulties and describe how to sample for them. It is critical that soil pests are detected early as options for remedial action post planting are extremely limited.

Damage symptomsSoil pests can reduce plant establishment, row density, and

plant vigour. Damage can occur both pre and post-emergence. During germination, pests may feed on the seed, tap root, or emerging cotyledons. Post-emergence, chewing on the hypocotyl may result in ‘felling’ of new plants or the grazing of root tips can cause constricted root expansion and symptoms akin to moisture stress. Affected fields will exhibit patchy emergence and/or stunted or dying seedlings. Plant mortality may continue until the plants reach early squaring.

Damage by soil pests is easily confused with symptoms caused by diseases such as black root rot, allelopathy from incorporated sorghum stubble, hypocotyl abrasion at the soil surface on crusting soils in windy conditions, or impeded root development due to subsurface compaction. Therefore it is essential in situations of poor establishment to closely examine the affected plants.

A key determinant is chewing or grazing damage on the hypocotyl or root sections. Obviously another key indicator is confirming the presence of soil pests with effective sampling.

Sampling proceduresSampling for soil insects is best conducted using a baiting

technique. Soil digging is potentially useful for confirming the presence of symphylans, but will not provide an effective measure of the abundance of insects such as earwigs and wireworms.

Conduct baiting as soon as practicable following planting rain or pre-irrigation:

O Soak insecticide-free grain seed (barley, wheat, sorghum) in water for at least two hours to initiate germination.

O Bury a dessert spoon-full of the seed under one cm of soil at each corner of a 5x5 metre square at five widely spaced sites per 100 hectares.

O Mark the position carefully as high populations of soil insects can completely destroy the baits.

O After five to seven days or upon seedling emergence, dig up the baits plants and count the insects present.Tests have shown that the type of seed used makes no

noticeable difference in attracting soil-dwelling insects. Recent research has shown that small to medium sized potatoes cut in half and buried in the same manner with the cut side facing down will produce comparable results to grain baits.

Some people may find the use of potatoes simpler as they do not require preparation compared to soaked grain and upon recovery of the baits, damage to the potato is also immediately obvious. Figures 1a and 1b show comparative results from a series of replicated fields comparing potato and grain baits for sampling wireworm and earwigs.

22 — The Australian Cottongrower August–September 2014

Planting cotton – have you baited for soil pests first?

O By Paul Grundy and Adam Quade, DAFF

FIGURE 1: Comparison between potato and soaked barley baits, (a) January 2014 and (b) April 2014. Potato performed well in these tests and may be more convenient to use than soaked grain.

Common soil pests

True and false wirewormsLarvae of the true wireworm Agrypnus sp. and false wireworm

species Gonocephalum spp. and Pterohelaeus spp. attack germinating seeds as well as the hypocotyl and roots of young cotton plants. Damage on individual plants may be observed at the soil surface as well as under the ground and often results in seedling death, young plant ‘felling’ and patchy plant stands. The adult beetles can also damage seedlings by chewing at or just above ground level.

August–September 2014 The Australian Cottongrower — 23

Excellent product. Excellent service.

Agriculture

A DIVISION OF

Australian made and owned

Cnr Buckland & Yaldwyn StsToowoomba Qld 4350

Phone: 07 4635 9872Fax: 07 4635 6633www.excelagr.com.au

Brian Moran 0427 722 925Dan Ryan 0427 700 779

Brian Moran

Dan Ryan

the way forward

Millennium Planter Rolling Cultivator Series 2000 Cultivator✓ Utilising the world renowned John Deere

metering system for superior seed placement✓ Designed by Australian farmers to reduce down

time and boost yields✓ Designed for dryland irrigation, contour

following or Tram Trak needs✓Twin 16” disc opener with walking depth gauge

wheels for greater reliability and accuracy✓ Full range of planter options available

✓ Easy to adjust tooling✓ Maximum weed kill✓ Maximum clearance✓ Fuel and moisture savings resulting from minimal

soil disturbance✓ Unique guidance system that can be adapted to

your planter✓ Reduces chipping costs✓ Cropshields to minimise plant damage✓ Large range of tooling options

✓ Construct and refine seed-beds prior to plantingfor enhanced seeding vigor

✓ Incorporate pre and post-emergence chemicalsfor fast knockdown and essential weed control

✓ Cultivate serious weeds while preserving seedlinggrowth and crop root systems

✓Aerate the soil, aiding water penetration andretention for young plants

✓ Help control soil and water losses from erosion,whilst managing residue retention

EXCEL PENETRATOR4 Available in 4, 6, 8 & 12 metres4 Side busting/centre busting capabilities4 Adaptable for gassing, dry fertiliser using Excel’s

Penetrator rig mounted fertiliser boxes4 5/8” inline sheer bolts4 Unrivalled trash clearance

A DIVISION OF GREAT WESTERN CORPORATION PTY LTD (ABN 91 064 434 475)

74–92 Buckland Street, Toowoomba Qld 4350

PH: 07 4636 9100FAX: 07 4636 9140 — www.excelagr.com.au

CULTIPACKER4 Available in 6, 8 & 12 metres4 Reduces the amount of water required to pre-irrigate as

the soil is a lot finer resulting in a more even moisture profile for better seed germination

4 Accelerates the breakdown of large clods in-field which promotes soil flow therefore trash incorporation

4 Large heavy duty rings for breaking clods from the top to the bottom of the furrow

FERTILISER RIGS4 Available for 6, 8 & 12 metre rows4 Up to 3 tonne capacity with exceptional stability and

ease of lifting4 Low draft shank and clamp assembly for simplistic

reliable operation4 Offering an unrivalled 770mm of underframe clearance

for brilliant trash flow4 Proven stainless steel metering units for corrosion

resistance4 Variable rate technology available4 Can apply gas at same time as fertilisers

ALSO AVAILABLE:4 Rubber Tyred Roller 4 Shielded Sprayer

EXCEL ALSO STOCK A WIDE RANGE OF SPARE PARTS

NEW

Parabolic shanks

for using less HP

& less fuel

ROLLING CULTIVATORS4 Construct and refine seed-beds prior to planting for

enhanced seedling vigor4 Incorporate pre and post-emergence chemicals for fast

knockdown and essential weed control4 Cultivate serious weeds while preserving seedling

growth and crop root systems4 Help control soil and water losses from erosion, whilst

managing residue retention…the Excel Rolling Cultivator will deliver

4 Revolutionary patent clean sweep assembly delivers a superior weed kill with minimum soil disturbance and minimal moisture loss

4 Large range of tooling options for cultivating, spraying and fertiliser applications

4 Crop shields to minimise plant damage and increase cultivation speed

E X C E L C U LT I VAT O R

FIXED BAR UNIVERSAL RIG4 Full cultivation 4 Fertiliser application4 Bed renovator 4 Fallow listering rig

STUBBLE WARRIOR4 Plant wheat back into cotton hill

4 Double disc 4 Single disc

4 Gassing and/or fertilising

A family owned businessAustralian owned & Australian made for over 80 years!

Brian Moran 0427 722 925Graham Easey 0427 700 779 (NSW)

Wireworm larvae (20 mm long).

The only way to effectively determine wireworm field populations is through the use of grain or potato baits. There are currently no specific thresholds for wireworms in cotton, but densities of one or more larvae per baiting site are considered damaging for summer grain crops.

Control is typically achieved with the use of in-furrow insecticide treatment at planting and therefore this pest must be detected before planting for effective control.

Black field earwigsAn occasional pest of seedling cotton, earwigs feed

predominantly on germinating seed and seedling roots resulting in poor establishment. Again, only effective bait sampling will detect this pest.

While there are no specified black field earwig thresholds for cotton, thresholds for maize and sorghum suggest that control maybe warranted when more than 50 earwigs are found across 20 baits or two to three earwigs per bait sample.

Black field earwig nymph (7 mm long).

The level of protection afforded by neonicotinoid cotton seed dressings for this pest particularly at higher densities is unknown. Given that earwigs need to feed on seedlings to acquire a lethal dose, it is likely under high pest densities that damage will occur. The application of insecticide treated grain baits at or prior to sowing may offer additional protection, as in-furrow insecticide treatments have been found to be generally ineffective for earwigs in grains where dense populations are present.

SymphylaSymphyla are white, soft-bodied ‘millipede-like’ arthropods,

three to seven mm long with 12 pairs of legs. Sensitive to light, they are very active when exposed. Symphyla are relatively common in most soils and generally feed on decomposing organic matter. Establishment problems in cotton due to symphyla have been previously isolated to some fields within the Theodore irrigation district, although they are recently suspected of contributing to damage in fields west of Moree and Dalby. Research into the pest status of this organism is underway.

Damage is likely to manifest as random patches of seedlings exhibiting apparent moisture stress and reduced vigour. Over time these symptom become more pronounced in affected areas, and in severe cases afflicted plants can senesce even though subsoil moisture is adequate.

Symphyla can feed on rootlets and root hairs with the result of continuous surface grazing causing either a ‘witches broom’ root system or a lack of lateral root expansion. Feeding generally appears to occur where the soil is moist and as the profile dries out, the continuous pruning of the roots can leave plants stranded in the top 10–15 cm of soil upon an otherwise full profile. Symphyla are very active and will move up and down in the soil profile to reported depths of below 0.8 metres.

Symphyla samplingThe detection of symphyla prior to planting is difficult as

distribution within a field is generally patchy. Although recent results with a specific sampling technique using potato and a ‘net’ pot has shown excellent success for attracting symphyla, the relationship between bait captured symphyla densities and potential for crop damage is unknown, and will be the focus of research during the 2014–15 season.

Where plants are showing symptoms of moisture stress or poor vigour, a basic soil survey will adequately confirm the presence of symphyla. Insert a shovel to full depth at the plant line on the hill and carefully lever the soil out so that it can be inspected more closely. Starting with the wettest soil, carefully break soil clods apart, keeping a close eye on the inner surfaces for movement. Symphyla are fast moving and will rapidly shift to avoid sunlight.

It is important not to confuse symphyla with other soil organisms such as diplurans or collembolans (spring tails). Diplurans closely resemble symphyla but are smaller, more rapid, and only have legs on the upper body. Symphyla have legs along the entire body and lack the long appendages at the end of the

24 — The Australian Cottongrower August–September 2014

Stunting of growth (right) associated with symphyla feeding on seedling root systems.

Symphyla damage to root systems. Feeding on the root tips (left) has resulted in a significant reduction in root area development.

Give’em the sucker punch!

®™ Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow.

For more information call 1800 700 096www.dowagrosciences.com.au

• Mirid control mid-season• Outstanding aphid control• No mite flaring• Good fit in Integrated Pest Management

(IPM) programs• New Mode of Action (Group 4C)

dipluran’s abdomen. Collembolans have a curved body and the capacity to jump when disturbed.

There are currently no registered control options for symphyla. Where damage is suspected, the use of irrigation may prove beneficial in assisting root pruned plants to establish. If damage is serious enough to contemplate replanting, wait for warmer conditions that will aid more rapid plant establishment or consider planting a fibrous root crop that is less likely to be affected. The impacts from symphyla have been managed at

Theodore by responding to tell-tale symptoms of moisture stress with timely irrigation and the avoidance of cool planting conditions.

Cultural aspectsA regular question asked by people is whether or not changes

to farming practices such as the greater retention of stubble is influencing overall soil pest abundance. In a general sense changes to tillage, soil applied pesticide usage, farm hygiene and stubble retention will affect the composition and abundance of soil pest species. For example, weedy fallows and generally poor levels of farm hygiene can encourage soil pests whereas clean fallows generally cause pest insect numbers to decline due to a lack of food.

The influence of field stubble in particular is contentious. Several studies have shown that while high stubble loads within fields will promote the abundance of soil pests, stubble can also provide a diversionary food source as well as increase the diversity of soil fauna such as predatory beetles (carabidae), centipedes, and earthworms. The incorporation of grain stubble prior to planting cotton may increase black field earwig populations whereas false wireworms are commonly found under a range of cultivation and stubble retention regimes. To simply associate stubble retention with increased soil pest activity would seem to be a too simplistic proposition at this stage and that perhaps the most prudent approach would be to pay closer attention to sampling soil insects where stubble is present prior to planting.

Our take home message is that as you consider planting in the months ahead, take the time to lay some soaked grain or potato baits as it is nearly always too late to solve soil insect pest problems once field symptoms occur.

26 — The Australian Cottongrower August–September 2014

A symphylan (left) is very similar in appearance to a dipluran (right), but has legs all along its body like a millipede and lacks the dipluran’s long rear appendages.

CHEMICAL ACCREDITATION

COURSESSt George 10/9 & 17/11, Dirranbandi 10/9 & 17/11,

Mungindi 10/9 & 17/11, Toowoomba 11/8 & 26/11, Dalby 12/9, Biloela 18/12, Theodore 18/12, Emerald 18/12, Moura 18/12,

Goondiwindi 9/9 & 18/11, Moree 8/9 & 19/11, Narrabri 5/9 & 20/11, Wee Waa 5/9 & 20/11, Gunnedah 24/11, Warren 28/8 & 21/11,

Narromine 29/8 & 21/11, Trangie 29/8 & 21/11, Bourke 3/9If dates/location do not suit please advise of your

requirements to enable future planningCourses can be arranged elsewhere if required

Accreditation valid for 5 years – One day New & Update courses

SUPERVISION SKILLS COURSEFormal management training for

managers, supervisors, leading hands or foremen Courses held as required

In-house courses can be arranged

Enquiries and Bookings:

Geoff Paton 1800 626 681Countryco Training Pty Ltd

Email: countrycotrain.audit@bigpond.comwww.countryco.com.au

Countrywide Industries

Manufacturers of Agricultural Equipment & General EngineeringFactory – Cnr River & Morgan Sts, Dubbo NSW 2830

PO Box 1830, Dubbo NSW 2830

Phone: (02) 6882 8933 Fax: (02) 6882 2106Email: cwi@hwy.com.au — www.countrywideindustries.com.au

PREPARE YOUR COUNTRY!

10-6HD – cutting width from 3 to 8.3 metres. Disc sizes 32”, 36”, 40”. Disc spacing 10.5”,12”.

Weight 1000 kg per foot of cut. 500 kg per disc

New Heavy Duty Model – up to 40

inch discs coming soon!