25
VII.
Codacide Oil Enhances Spreading and Coverage:
The UK Ministry of Agriculture, Fisheries and Food and Bristol University’s Long Ashton Research
Station assessed the affect of adjuvants on the spreading and coverage of aqueous sprays on foliage
of barley and peas (MAFF, 2000).
Deposit counts and mean deposit areas provided an estimate of
adjuvant coverage performance in terms of the number and sizes of spray droplets retained,
together with a measure of their subsequent spreading and / or coalescence.
Table 3:
Adjuvant effects on the spray coverage of pea leaves after application with an even spray
nozzle.
Additive
Mean Deposit Count
(MDC) (for 500 mm
2
)
Mean Deposit Area
(MDA) (mm
2
)
Coverage (% leaf
area)
a
None
–
Water alone
79
0.02
1.12 (0.3)
Actipron Mineral Oil
500
0.08
1.91 (6.7)
Codacide Oil
592
0.13
2.60 (13.4)
Note:
a
In values for statistical analysis; back-transformed values in parenthesis
As summarized in Table 3, Codacide Oil (10 g l
-1
) improved coverage performance on pea leaves by
assisting to optimize the number and size of spray droplets with a 592 Mean Deposit Count (MDC), a
coverage of 0.13 mm
2
Mean Deposit Area (MDA) per droplet representing 13.4 % leaf area on spray
coverage of pea leaves as compared to water alone of 79 MDC, 0.02 MDA, and 0.3 % leaf area
coverage; and as compared to mineral oil Actipron of 500 MDC, 0.08 MDA, and 6.7 % leaf area
coverage.
Similarly, Codacide Oil significantly increased the coverage performance on barley leaves as
compared to water alone and the mineral oil Actipron (refer Table 4).
Codacide not only assists
spray performance in terms of number and size of spray droplets but also improves spread of
droplet on impact as compared to water alone and mineral oil Actipron (MAFF, 2000).
Baker (1994)
showed how the spread of the growth regulator chlormequat on wheat leaves was increased by an
average of 8-9 times by the addition of Codacide.
Table 4:
Adjuvant effects on the spray coverage of barley leaves after application with an even
spray nozzle.
Additive
Mean Deposit Count
(MDC) (for 200 mm
2
)
Mean Deposit Area
(MDA) (mm
2
)
Coverage (% leaf
area)
a
None
–
Water alone
21
0.02
-1.44 (0.2)
Actipron Mineral Oil
156
0.05
1.25 (3.5)
Codacide Oil
217
0.12
2.56 (13.0)
Note:
a
In values for statistical analysis; back-transformed values in parenthesis
Droplet spreading is influenced greatly by the surface tension of the liquid applied (Holloway
et al
,
2000).
Surface tension and contact angle are important as the surface tension influences droplet
spectrum and retention, whilst the contact angle indicates the degree of spread of droplets (refer Fig
1 & 2).
As seen in Fig. 3 & 4, Codacide plus PPP forms a thin amorphous film that envelopes the
stomata (Fig. 3) and their individual guard cells on wheat leaves (Fig. 4).
Codacide Oil and Glyphosate had a lower surface tension (0.037 Nm
-1
) and contact angle (53
o
) than
Water and Glyphosate (0.048 Nm
-1
) and (66
o
) respectively (Wells, 1989).
Dynamic Surface Tension
(DST) values at a surface age of ca 50 ms were recorded by Holloway
et al
(2000) that showed
Codacide to have a significantly reduced DST of 59 mNm
-1
, as compared to the mineral oil adjuvant
Actipron of 69 mNm
-1
and of water of 71 mNm
-1
.
