2016 Sorghum Sugarcane Aphid Research Exchange

1. Key question #3: Combination of
harvest aids with insecticides
Nick Seiter
University of Arkansas
Sorghum – Sugarcane Aphid
Research Exchange Meeting
New Orleans, LA
January 7 – 8, 2016

2. Introduction
• Sugarcane aphids can cause mechanical
problems & delays when present in grain
heads and/or flag leaves at harvest
• Some reports of harvest aid applications
driving aphids into the grain head,
exacerbating the problem
• Available insecticides have pre-harvest
intervals that complicate their use with harvest
aids
– Transform is shortest at 14 d; Sivanto 21 d
– Glyphosate and sodium chlorate: 7 d

3. Photo: Robert Goodson, UA Cooperative Extension

4. Materials & Methods
• Field identified that was ready for harvest aid
application & had high densities of sugarcane
aphids
– Several trials planned; single location where proper
conditions occurred
• Applied treatments on 1 Sept. 2015
– Untreated
– Transform (1 oz./acre)
– Glyphosate (32 oz./acre)
– Sodium chlorate (4 qt./acre)
– Glyphosate + Transform
– Sodium chlorate + Transform
• Sampled aphids on 4 Sept. & 14 Sept.
– Counts on flag leaves & grain heads of 10 plants/plot
• Harvested 15 Sept.

5. 0
50
100
150
200
250
300
350
400
1-Sep 4-Sep 7-Sep 10-Sep 13-Sep 16-Sep
Aphidsperleaf
14 Sept.
(13 DAT)
Aphid densities on flag leaves
Rohwer, AR 2015
Untreated
Transform
glyphosate
sodium chlorate
glyphosate + Transform
sodium chlorate + Transform
a
b
4 Sept.
(3 DAT)
F = 15.06
P < 0.001
1 Sept.
(Treatments
applied)

6. 0
10
20
30
40
50
60
70
80
90
100
1-Sep 4-Sep 7-Sep 10-Sep 13-Sep 16-Sep
Aphidspergrainhead
14 Sept.
(13 DAT)
Aphid densities on grain heads
Rohwer, AR 2015
Untreated
Transform
glyphosate
sodium chlorate
glyphosate + Transform
sodium chlorate + Transform
4 Sept.
(3 DAT)
F = 1.524
P = 0.241
1 Sept.
(Treatments
applied)

7. 0
20
40
60
80
100
120
140
Untreated Transform glyphosate sodium chlorate glyphosate +
Transform
sodium chlorate
+ Transform
Bushelsperacre(14%)
Grain Yield
Rohwer, AR 2015
F = 2.25
P = 0.103
• No mechanical/clogging issues occurred at harvest

8. Key Learnings
• Sodium chlorate resulted in reduced
aphid populations, while glyphosate
did not
– Quicker dry-down
• Insecticide applied with harvest aid
dramatically reduced aphid
populations
• No aphids left in the field after 13 d
– Population collapsing?

9. Observations from 2015
• Harvest problems occurred more
frequently in earlier planted sorghum
– Developmental stage of sorghum when
aphid populations were rapidly
increasing (early August in AR)
• Uncertainty among growers &
consultants on need for insecticide
based on number of aphids at
maturity

10. Next Steps
• Develop an action threshold for harvest aid
applications
• Determine how long aphids remain on plant after
a successful harvest aid application
• Effect of honeydew on efficacy of harvest aids

11. Discussion