Sorghum Tips

Sugarcane Aphid: Update, Outlook, and Early Season Thoughts on Management

This tip was provided by:

Robert Bowling, Extension Entomology, Corpus Christi, (316) 946-0329, robert.bowling@ag.tamu.edu

South Texas

Sugarcane Aphid: Update, Outlook, and Early Season Thoughts on Management

Sugarcane aphid is building populations on overwintering hosts from the Lower Rio Grande Valley up through the Coastal Bend of Texas.  Dry conditions and unusually high temperatures in the Valley have allowed farmers to get a big jump on seeding the 2017 sorghum crop.  Sorghum seeded early in February has emerged and conditions are favorable for rapid growth—also favorable for an early-season infestation by SCA.  This may be a harbinger of things to come for south Texas sorghum producers.

It is too early to say with certainty SCA will pose more an issue for sorghum producers in the Valley (and for south Texas) in 2017 than in 2016, but it is always a good idea to scout sorghum early and often for early aphid detection.  An insecticide seed treatment will provide approximately 30 to 50 days of protection from the planting date against SCA.  Start monitoring sorghum about three weeks after planting for early detection of SCA, for early season infestations which usually start on field edges especially where overwintering hosts such as volunteer sorghum or Johnsongrass are present. Always check field borders for SCA.

Many sorghum producers are moving toward sorghum hybrids with ‘high tolerance’ to sugarcane aphid.  Many of these hybrids in multi-state university testing programs have demonstrated their value when compared to an SCA susceptible hybrid.  Sugarcane aphids can be found on ‘highly tolerant’ sorghum hybrids, but their population growth is much slower than growth on susceptible hybrids.  Regardless, all sorghum should be routinely scouted for SCA.  Check with your seed rep before purchasing any sorghum hybrid.  They will have the knowledge of each product’s performance potential and placement not only within a region but within fields on your farm.  A list of sorghum hybrids for 2017 that have been identified as having sugarcane aphid tolerance is posted by United Sorghum Checkoff Program, http://www.sorghumcheckoff.com/farmer-resources/grain-production/hybrid-selection (From the 2016 list of 21 hybrids, 15 remain, six have been deleted, and 12 new hybrids were added for 2017, as of Feb. 28.)

Keep in mind that you are paid on pounds of grain produced and not the tolerance of your hybrid to sugarcane aphid.  We would not suggest abandoning a high performing SCA susceptible hybrid for an unproven hybrid with SCA tolerance.  Remember that SCA management is highly dependent on early detection and routine weekly or twice weekly scouting to treat when populations reach an economic threshold of 50 to 125 aphids per leaf (average of sampled plants; remember, this is a South Texas threshold, the threshold for the High Plains is lower).  Treatment must be applied within 3 to 5 days of reaching a threshold to prevent populations from reaching economically damaging levels.  Remember that carrier volume is extremely important to maximize penetration of the insecticide into the canopy (10-15 gallons/A by ground and 5 gallons/A by air).

Fungal Infection of Sugarcane Aphid, South Texas, 2016

I recently wrote about an epizootic fungus occurring in an insecticide efficacy trial in 2016 which colonized sugarcane aphids.  The fungus responsible was Lecanicillium lecanii.  Is this possibly a means of managing SCA?  Although epizootic fungi are highly effective for SCA (and other pests) management, their occurrence is very dependent on very specific parameters.  At this time, our observations on this fungus are limited to a small area of Texas in 2016.  It remains to be seen if it will be present let alone have an impact on Texas sorghum in 2017.  Currently, it is not clear if the fungus could be managed by producers for control of SCA.  For further reading on the fungus, see newsletters 1.7 & 2.1 at http://betteryield.agrilife.org/newsletters/

For more information on sugarcane aphid and other sorghum pests in South Texas please visit our website at http://betteryield.agrilife.org.