Insect Strip

Insect Strip

Wednesday, October 22, 2014

Update on Sugarcane Aphids on the Texas High Plains

It has been six weeks since the sugarcane aphid was officially reported in grain sorghum (Floyd County) on the Texas High Plains. Since that time the aphid was also found in Hale, Swisher, Briscoe, Lubbock, and Crosby counties. Blayne Reed, Extension Agent IPM for Hale and Swisher counties has been monitoring the aphid distribution and population buildup. Just in the past two weeks he has seen a rapid increase of aphid numbers in several sorghum fields (including forage sorghum). Because of this Kerry Siders, Extension Agent IPM, started a road survey on October 21 along FM 168 checking fields a second time in Castro, Lamb, and Hockley counties. Just 18 days from his previous survey he sampled 23 locations and found sugarcane aphids in 12 locations in Castro, Hockley and Lamb counties. The heaviest concentration was in Lamb county. He was concerned about infestations in a few fields. In one field near Olton the infestation was so heavy that for the 50 leaves sampled, he found thousands of aphids per leaf.

Last week on October 16, I did a road survey from Pampa (Gray county) through Carson, Armstrong, and Randall counties. Some sorghum fields were fenced in and I wasn’t able to look closely, but of the fields I could walk through I did not find any sugarcane aphids nor saw any evidence of honeydew accumulation on leaves.

Still with the expanding distribution of this aphid, I would encourage field scouting of grain and forage sorghums, particular, in Bailey, Parmer, Deaf Smith, Randall, Armstrong, Donley, and Hall counties. But, there could be pockets of sugarcane aphids all across the Texas Panhandle. If infestations are found or suspected, please contact your County Extension Agent and/or me at (806) 677-5600, ext 612, or to document the infestation and help with management decisions. Also, we would be interested in monitoring the ability of the aphids to overwinter.   

One issue concerning control of this aphid, if an application is needed, is that chlorpyrifos and dimethoate do not provide good control. Transform has been approved for a section 18 emergency use and it does provide good control. The supply of Transform may be limited in our area if sugarcane aphid infested fields do need to be controlled.

 The following is the recent newsletter (Plains Pest Management, October 20, 2014) by Blayne Reed. It has good information on current conditions, action thresholds and management options. I appreciate Blayne for allowing this information to be reprinted in this issue of the Texas Panhandle Pest News. 

Sugarcane Aphid Threat (Plains Pest Management, October 20, 2014)

In early to mid-September we confirmed the presence of this aphid in Hale, Swisher, & Floyd counties. Over the next few weeks, we watched and documented as the sugarcane aphid infested field after field of our program’s late planted sorghum fields. This infestation was sub-economic and appeared to be isolated to small hot spots within fields. Very little increase in size of colonies was observed in infested fields yet the aphids continued infesting new fields from east to west across our counties. We remained confident that they would not be an economic problem for a multitude of reasons, one of which being our cooler temperatures but were certainly worth keeping an eye on. For this reason we remain active in scouting late planted sorghum fields for the sugarcane aphid. It is a very good thing we have. This aphid could be growing into a major problem this season. Based upon this aphid’s history farther south, they could grow into that problem in just a matter of days.
In the past two weeks I have seen some of our earliest sugarcane aphid infested field, in southeastern Swisher, increase from small hot spots with 20 to 40 aphids on the lower green leaves to 100% in-field plant infestation at that 20 to 40 aphid per lower leaf level and complete plant coverage from lower leaves to flag leaf coverage in those old hot spots. In those hot spots, we already have desiccated plants and minor lodging.

This increase does not look to be slowing, but rather growing exponentially. Of our program’s late sorghum fields, we have 98% of our fields infested at some level today. A number of these fields (I now estimate 20 %) have aphids covering the under- side of leaves on the bottom half of all the plants with the old hot spots climbing higher. These fields, with this level of pressure, could be a very serious problem is left unattended while we wait for the fields to dry for harvest. Reports indicate that from this level, the sugarcane aphid can increase to cover the entire plant, head and panicles included, in a matter of days. This would certainly be an economic problem and is very likely to cause harvest problems similar to what occurred in the Lower Rio Grande Valley last year.

I URGE all producers and consultants to take a few minutes and give sorghum and sorghum like hay crops a good walk through looking for these aphids. This weekend I stopped by a field of dryland haygrazer that was green and nearing boot less than a week ago. Saturday, it had the look of a field that had been ‘frosted.’ Upon close inspection sugarcane aphids had completely covered the plant causing desiccation and plant death. Lodging had already begun. 

If your sorghum field is nearing the situation I described earlier and have sugarcane aphids nearing flag leaf you now have three options. You could also only have a few days to act while the crop is a few weeks away from being dry enough for harvest.

1. If the action threshold of 40% plants infested with 100 aphids per leaf (average top, middle, and lower) has been reached: Make the application of Transform @ 1 ounce per acre. This is our only proven bullet to control this pest for this season, if coverage is good enough (10 GPA ground, 5 GPA air). It is fairly expensive and comes with a 14 day pre-harvest interval. For those not wanting to make this kind of investment this late with grain prices so low, there are options 2 & 3.

2. Harvest early: Take the dock at the elevator rather than loose so much yield to the aphid. This aphid can also cause serious lodging and ‘gummy harvest’ issues and losses pushing 60% of yield potential.

3. Harvest aid the infested sorghum field: Treatments of Aim or Roundup might help dry the plant faster and leave the aphid with nothing to feed upon. This was tried with limited success in the LRGV in 2013. Aim would certainly act faster.

For haygrazer, option 2 might make the most economic sense.

In our program field in southeastern Swisher, our producer chose option 2. This field was just days from being ready when the rapid increase in sugarcane aphid numbers was noted. This field was harvested without incident. In our program, we currently have 4 more fields nearing this level of infestation that are a few weeks away from being harvest ready. I will be checking them twice weekly.

Sugarcane Aphid Colony (Photo: Dr. David Kerns)

Sugarcane Aphid Damage (Photo: Dr. David Kerns)