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Sugarcane Aphid Update

–By Dr. Sarah Zukoff, Dr. J.P. Michaud, Dr. Brian McCornack and Dr. Wendy Johnson

  1. First report of sugarcane aphid on grain sorghum in Kansas this year

The sugarcane aphid (SCA) has now been reported in Sumner County. Sorghum producers in Kansas should begin scouting their fields on a routine basis. More information on scouting and thresholds for treatment can be found in the Agronomy eUpdate article “Start scouting soon for sugarcane aphid” from July 7, 2017, and at the myFields web site at: https://myfields.info/pests/sugarcane-aphid

 

 

Figure 1. Current status of the SCA. The map indicates only the counties in which the SCA has been found, and does not indicate how many or how few aphids were found in that county. Source: https://www.myfields.info/pests/sugarcane-aphid

 

 

Chemical control

Two insecticides are labeled for use on sugarcane aphid on sorghum in Kansas this season:

Sivanto (flupyradifurone)
4.0 – 7.0 fl oz/acre (0.052 – 0.091 lb ai/acre)

Transform (sulfoxaflor)
0.75 – 1.5 oz/acre (0.375 – 0.75 oz ai/acre)

Field trials show good efficacy of the above materials against the sugarcane aphid. Both have the ability to penetrate leaves through translaminar movement and kill aphids feeding on the undersides.

Maximum efficacy will be achieved by application in a large volume of water, preferably 20 gallons per acre or GPA (minimum 10 GPA) by ground or 5 GPA from the air. Laboratory trials indicate that Transform (sulfoxaflor) is relatively safe for important aphid predators such as lady beetles and lacewings and thus can be considered IPM-compatible. This is true to a lesser extent for Sivanto (flupyradifurone), but various trials have indicated a much longer period of residual activity for this material.

Both insecticides have annual application limits and growers are advised to rotate them if follow-up applications are required. Note also that preharvest intervals will be a factor to consider when treating late-season infestations, so applicators should read labels carefully and keep a log of all treatments for each field. Because Transform and Sivanto are absorbed by leaves and eventually metabolized by the plant, reinfestation can occur if large numbers of winged aphids continue to settle in the field.

When inspecting fields for treatment efficacy, note whether any live aphids are winged or wingless, as the former may indicate continued immigration rather than control failure. DO NOT attempt to control sugarcane aphid with contact insecticides that have broad-spectrum activity; these include all pyrethroid and organophosphate materials and combinations thereof. Replicated field trials indicate these materials are not effective, harm beneficial species, and often result in higher aphid numbers than unsprayed control plots.

Sorghum headworm infestations are often present when SCA is observed in a field, since this pest migrates using the same weather events. When choosing an insecticide to control headworms, use products that are less harmful to natural enemies such as Prevathon or Blackhawk, as these have proven compatible with Transform and Sivanto and less selective materials risk flaring the aphids.

The myFields web site: Keeping updated on SCA in Kansas and reporting findings

For ongoing current information on SCA in Kansas, check out the myFields web site often in the coming weeks and months: https://www.myfields.info/pests/sugarcane-aphid

It would be helpful if producers would report findings of SCA in their fields on the myFields web site as soon as the insects are found. Reports of findings are used in developing the map seen in Figures 1.

The reports used to develop each map are, in part, those submitted through the myFields web site from account holders that also have special permissions as “Verified Samplers.” Only reports submitted by these verified samplers get mapped so that we can account for data quality. However, we do encourage any account holder to report their observations on the SCA. Web site administrators can see these reports and can contact the submitter for a confirmation, a great way to get an early detection in new areas. Web site visitors will need to: 1) sign up for an account, 2) log in, 3) to get access to the ‘Scout a Field‘ feature to make reports. The Scout a Field tool is easy, you just map the observation location and select yes or no for SCA presence.

Here is the sign up page: https://www.myfields.info/user/register

Also, if sorghum producers are interested in receiving alerts, which are triggered by new reports submitted by verified samplers, they just need to sign up for a myFields account. Signing up for an account automatically signs them up for SCA alerts, but they can also opt out of them in their user preferences. The alerts include a statewide email notice when SCA is first detected in the state, and then are localized by county as SCA moves into the state. The notices will also contain latest recommendations and contact info for local Extension experts.

 

Sugarcane Aphids

–by Dr. Jeff Whitworth, Dr. Holly Schwarting and JR Ewing

Sugarcane aphids were still active in north central KS on 23 and 27 October, as were the beneficials (see pics).  Fields were being harvested and getting acceptable yields (growers reported 80 to 160 bu/acre, which they said was usual for the fields involved) without much interference caused by the stickiness of the honeydew (and it is sticky).

SCA Oct_leaf

 

SCA oct head

 

beneficials - aphids

Below are the results of sugarcane aphid efficacy trials conducted in Saline Co.  Aphid populations were, in our opinion, ideal for conducting trials of this nature because there were enough aphids to show any differences caused by the treatments, but not so many that the plants were overwhelmed or that the grower sprayed the field (thereby over-spraying these plots).

SCA efficacy trial 1

 

Means within a column followed by the same letter are not significantly different (P>0.05; PROC ANOVA; Mean comparison by LSD [SAS Institute 2003]).

SCA efficacy trial 2

 

Means within a column followed by the same letter are not significantly different (P>0.05; PROC ANOVA; Mean comparison by LSD [SAS Institute 2003]).

Sorghum Headworms

–by Dr. Jeff Whitworth and Dr. Holly Schwarting

Sorghum headworm (corn earworm, fall armyworm) populations continue to cause much concern throughout south central and north central Kansas.  Sorghum is most vulnerable to headworms from flowering to soft dough.  The general rule is that headworms may cause 5% loss per worm per head during the approximately 2 weeks the worms are feeding directly on the grain.  So early detection, while the larvae are small, is always recommended, and thus if treatment is justified, control will be achieved before maximum damage is realized.  For more information on sorghum headworm and control options, please visit: http://entomology.k-state.edu/extension/insect-information/crop-pests/sorghum/cornearworm.html

CEW_sorghum head

 

fall armyworm_sorghum head

Alfalfa – Weevils and Aphids

—Dr. Jeff Whitworth – Dr. Holly Schwarting – J.R. Ewing and Salehe Abbar

Alfalfa weevil feeding is winding down in north central Kansas, but not as fast as usual. If treatment is still considered prior to swathing do not forget to read the label and follow the PHI (post-harvest interval) required by the product you choose. The untreated control plots in our insecticide efficacy trials are still above our treatment threshold of 1 larva/2 stems, or 50% infestation, and contain many small larvae. Remember, larvae were 1st detected on 13 March so they have been actively feeding for six weeks. However, the good news is many insecticides are still providing excellent protection from one application three weeks ago. See below:

Screen Shot 2015-05-02 at 9.46.15 AM

Aphids continue to increase in alfalfa fields. They are primarily pea aphids with a few spotted aphids. Have not seen or heard of any at, or even close to, treatment thresholds, but populations are increasing. Lady beetle and parasitic wasp populations seem to be rebounding which should help slow down these aphid populations.

 

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