Toward new sowing systems for

aerial baiting.

Landcare Research Workshop, Lincoln,

16 November 2009

G. Nugent

Landcare Research P.O.Box 40, Lincoln

Aerial baiting

• Cheapest baiting system

• Since 1990s GPS guided

helicopters using buckets with

spinners to broadcast bait has

become the norm

Fixed wing rarely used now

Driven by belief that thin even

spread of bait by broadcasting

has to be best (less chance of

bait gaps)

Results in very limited ability

to precisely control bait

placement (equated by some

to carpet bombing)

Otago Daily Times 21/01/2008

Threats to aerial baiting

• 1080 poisoning controversial - environmental

contamination, non-target by kill, not most humane

– Continued use requires reducing the actual and perceived risks

– Ideally should use far less 1080, less often

Our core question:

• Can sowing rates be reduced much more?

– Simple calculations suggest YES

– Usually only <10 possums+rats per ha yet 200-500 individually

lethal baits/ha usually sown

=> Why is such overbaiting needed?

Fragmentation hypothesis

• GPS-guided baiting ensures all

possums encounter toxic bait, but

some still survive because they

need to quickly encounter 2 or

more baits to be killed

– This need v is because possums have to find a lethal

dose within 30-60 minutes

– And some sub-lethal bait fragments are produced

during (or after) sowing

=> High bait density (and/or prefeeding) is needed to

ensure high encounter rate

New Creek 2008

12g RS5,150m swath,

fast spinner

(NB: worst example),

=> shows lots of very

small 0-2g fragments

created during (or after)

sowing

Fragmentation

Evidence

RS5 bait distribution before sowing

0

10

20

30

0-1 2-3 4-5 6-7 8-9 10-11 12-13 >14

weight (g)

% o

f b

ait

s

RS5 bait distribution after sowing (on road)

0

10

20

30

40

0-1 2-3 4-5 6-7 8-9 10-11 12-13 >14

weight (g)

% o

f b

ait

s

Coverage question

• If overbaiting needed

because of fragments, is a

high bait density needed

everywhere?

=> What if bait was sown in

high density strips or

clusters rather than

broadcast?

Broadcast flight path map

showing total coverage,

Molesworth, 2008

How does fragmentation occur?

• Three possibilities

– Before sowing

– During sowing

– After sowing

How does fragmentation occur before sowing?

• Fracture lines created during extrusions

– Baits simply crumble under weight/pressure

• Rough handling/abrasion in in bags

– Knocks ends off baits

• Some pellets break apart during pouring into hoppers, or

larger containers

– Some evidence this is worse for RS5 and where bait is stored for

long periods

– Possibly/probably worse if bait softened by previous dampening

(e.g. w deer repellent)

How does

fragmentation

occur before

sowing?

• Counterproductive focus

on efficiency through

mass handling

•Not suited to current bait

types

•But ok w shatterproof bait

How does fragmentation occur during sowing?

• As they tumble down the

bait column in the hopper

– Lot of pressure on baits at

bottom of bug hoppers

• As they hit the high speed

spinner

– The higher the speed the

worse the problem

• As they hit bucket legs

(where not retractable)

Spinner 1350 rpm

0

50

100

-100 -50 0 50 100

Distance from flight path (m)

N b

ait

s

Spinner 950 rpm

0

50

100

-100 -50 0 50 100

N b

ait

s

All apple eaten

0

50

100

Unp

oiso

ned

3.0k

g/br

oadc

ast

0.25

kg/a

ligne

d

0.25

kg n

ot a

ligne

d

Carrot

Apple

Cereal

All carrot eaten

0

50

100

Unp

oiso

ned

3.0k

g/br

oadc

ast

0.25

kg/a

ligne

d

0.25

kg n

ot a

ligne

d

Carrot

Apple

Cereal

How does fragmentation occur after sowing?

• Partial consumption by rats/mice?

Fragments left by a possum

How does fragmentation occur after sowing?

• Competition between possums for a single bait

How does fragmentation occur after sowing?

• Caching by rats/mice may quickly reduce the amount of bait

available – decrease possum encounter rate?

Possums

0% 2% 4% 6% 8%

Residual mRTCI

Results 1: Whirinaki 2007

• Bait sown aerially in

strips, or broadcast, or

placed by hand in clusters

=> strips and clusters fine

for possums and rats (at

100m flight path spacing)

- with prefeed

- even with only

0.4kg/ha toxic

Complete coverage

not essential for

possums or rats

No Prefeed, 0.4kg/ha clusters

Prefeed, 0.4kg/ha clusters

Prefeed, 2.0kg/ha strips

Prefeed, 2kg/ha broadcast

No prefeed, 2kg/ha broadcast

Aerial sowing

in clusters

• SowLow bucket– Originally designed to

improve control of sowing rate

– previously used with spinner

• Redesigned to sow clusters– Spinner removed, timed

gate added under wheel

– For Molesworth, delivered clusters of 35-40 8g baits every 30m(1kg/ha)

Cluster sowing, Isolated Hill

Results 2: Post-control possum abundance

(RTCI), Molesworth

=> With no prefeed, no consistent difference

between 2.5kg/ha broadcast and 1.0kg/ha cluster

Low coverage treated only habitats with predicted RTCI > 10% RTCI, high coverage treated habitats >5% RTCI

0.8%

1.1%

0.5%

1.8%

0.0%

0% 1% 2% 3% 4% 5%

Broadcast High

Coverage

Broadcast Low

Coverage

Cluster High Coverage

Cluster Low Coverage

Cluster w Prefeed

Residual Trap Catch Index (%)

0.9%

1.1%

0.0%

0% 1% 2% 3% 4% 5%

Broadcast

No Prefeed

Cluster No

Prefeed

Cluster w

Prefeed

Residual Trap Catch Index (%)

Results 3: Landsborough(b) Reduction in CTC activity

0% 50% 100%

Not Aligned

Cluster

Aligned

Cluster

Not Aligned

Broadcast

Reduction in CTCI

(a) Residual Trap Catch

0% 5%

Not Aligned

Cluster

Aligned

Cluster

Not Aligned

Broadcast

RTCI

Std 3kg/ha

broadcast with

no prefeed

alignment

Clustered 0.25

kg/ha with

prefeed

alignment

Clustered 0.25

kg/ha with

no prefeed

alignment

Std 3kg/ha

broadcast with

no prefeed

alignment

Clustered 0.25

kg/ha with

prefeed

alignment

Clustered 0.25

kg/ha with

no prefeed

alignment

Similar kills with either broadcast or cluster+aligned prefeed,

even though 92% less toxic bait used

=> possible to reduce the amount of 1080 by > 95%?

Low Sow summary

• Early days, but it does appear that the amount of 1080

needed can be greatly reduced with some simple

changes in sowing method and how prefeed is used.

potential for major cost savings

should reduce many (but not all) of the actual and

perceived risks associated with this tool

same principles will also make aerial baiting (with 1080

or any other poison, biocontrol, or Tb vaccine) much

cheaper than now

3. New sowing technologies

LR-industry partnership w AHB-funding for field testing– Directions not yet finalised

– Four possibilities to be explored

1. Shatterproof baits - able to

broadcast at low density

Big buckets and helicopters, but no

control of placement

2. Strip sowing of current baits

Fixed wings with 2 tonne hopper fly at

150kph, 150m spacing = >2000ha per

hour – 4000-8000ha per plane load!

New sowing technology (2)

3. Cluster sowing of small 2-4 g baits at low rates (<100g/ha)

small buckets and helicopters -

1000ha/ha = <$1/ha per pass cf $2.50-

$5.00 for current ops.

4. Simultaneous pre-fed in moderate

swaths with clustered toxic

Moderate buckets and helicopters –

single pass = low cost

New sowing technology (3)

Also: GPS control of cluster placement

• GIS/GPS control of bucket gate stops clusters being sown within

(say 50m) of any creek or track designated in the GPS

• Already routine for fertiliser application

• World leading GPS capability in NZ (Tracmap Dunedin and others)

New sowing technology (4)

Aim is to produced a hi-tech precise sowing system that:

– Places a small amount of bait in clusters at known locations

– Puts bait in only 2-3% of the landscape

– Does not not include any mappable waterways or tracks.

Coupled with small bait sizes and ultra-low sow rates

allows small helicopters and should reduce flying and

bait costs greatly.

– Makes more frequent use of aerial poisoning affordable and

yet still uses less 1080 –2-3 year cycle feasible for rats?

– Makes use of expensive toxins affordable

• Cholecalciferol

• New high tech toxins/vaccines/immunocontraceptives

Potential new applications

• Better delivery of old agents

– Screening out fragments at bottom of bucket

• Should be technologically simple?

• Holey converyor belt from buckt to offset spinner?

• Need for fragment reservoir under bucket?

– Need to increase precision of placement

Precise bait placement

The challenge: No 1080 in waterways

Precise

placement

• 50 m either side is too wide?

• Need very low flying

– Just above canopy?

• New very slow flying?

– 20-30knots?

– To minimise bait deviation

from trajectory?

Potential new applications

• Delivery of expensive new agents

– live BCG vaccine in a sachet

• ‘difficult to sow’ bait carriers

– Oral forms of fertility control

– Expensive ‘new’ toxins

• Connovation shatterproof bait

• Chole bait @ $20/kg

• Long life chole gel

Suggested directions

• Industry to work with bait manufacturers on sowing systems for

shatterproof baits

– Further development of current broadcasting technology by industry

• Bigger gentler spinners

• Industry to develop strip and cluster sowing solutions for current

baits

– Gentler spinners

– Optimisation of ability to align prefeed and toxic

– Optimisation of flight path spacing

– Fixed wing solutions?

Suggested directions (2)

• Precise placement of clusters/individual baits at

recorded locations

– LCR + industry + GPS/GIS technologists

– Development of ideal bait for this app.

• 5 g, durable, 0.25% 1080

• Requires long regsitration

• Dual agent or bait type delivery

– LCR + industry