Have a Plan for Managing Sugarcane Beetles in Field Corn

Adult Sugarcane Beetle

Sugarcane beetles (Euetheola humilis rugiceps), have caused many Mississippi corn producers major headaches in the last decade. Ironically enough, most of the problem areas are in the Hill region of the state and not the Delta region. Sugarcane beetles are certainly present in the Delta but rarely cause widespread problems in corn (to date). Sugarcane beetle infestations are sporadic in nature but heavy infestations can be very serious and require replanting in some situations. Unfortunately there are no viable rescue treatments available, so this pest has to be managed at planting.

Biology:  Sugarcane beetles are scarab beetles similar to the June bugs we see at our lights every year. We collectively lump scarab beetle larvae into a group called “white grubs” in which many are pest of row crops. However, with sugarcane beetles it is actually the adult that causes the damage. Sugarcane beetles have only one generation per year.  They emerge in the spring, find suitable host plants (corn in many cases), females lay eggs where the immature grubs take around 85 days to develop and pupate.  New adults emerge in September and October (I often see emerging sugarcane beetles by the thousands in September at football games coming to the lights) and seek overwintering quarters, which are often grassy areas or pasture land, and the process starts over again the following spring.

Injury:  Adult sugarcane beetles dig down approximately ½ inch below the soil surface and feed on the stem of the corn plant. In severe infestations there can even be multiple beetles feeding on the same plants. Stem feeding can range from just breaking the stem surface to feeding all the way through the stem. Most infestations occur from V2-V5 growth stage. We have observed that when sugarcane beetles feed at least half way through the stems it usually results in dead heart or severe stunting and suckering.  Often times “light” feeding (partially breaking the surface of the stem) will result in delayed injury which may not be fully apparent to V8 or V10 growth stage.  The problem with delayed injury is when you finally realize you have a problem and need to replant, we are usually well past recommended planting dates and herbicides have been applied that lock you into corn that generally does not yield nearly as well planted late.

Symptomology:  Below ground feeding by sugarcane beetles can cause numerous above ground plant responses depending on the severity of the feeding. Above ground symptomology may include; slight stunting, slight chlorotic leaf streaking, heavy stunting and chlorotic leaf streaking, suckering plants, and dead heart. In some cases plants can be damaged below ground and no visible above ground symptomology is apparent at all.

Who should take extra precautions at planting?  We have worked extensively over the last few years with sugarcane beetles in field corn. We have found that because of their sporadic nature, predicting outbreaks or problems is nearly impossible. Just because you had them last year does not mean you will have them this year.  Just because you did not have them last year does not mean you won’t have them this year. However, if you ever had them, one thing is for sure, you will never forget them and are likely to want to take extra precautions at planting to reduce your risk of having them again. We have noticed that no-till or minimum-till fields are at higher risk of infestation (from all soil insects), but have seen severe infestations in conventional till fields as well.

Treatment Options:  Remember there are no viable rescue treatments for this pest. Given that sugarcane beetles have to be controlled at planting, you basically only have a few options; seed treatments, granular insecticides, in-furrow sprays, or combinations of these.

Seed Treatments:  There are many seed treatment offerings in corn to control below ground pest and efficacy is fairly similar with most soil insect pests we face in Mississippi with the exception of sugarcane beetles. With sugarcane beetles we have seen improved control with the active ingredient clothianidin, particularly at the higher use rates such as 500 or 1250. Clothianidin is the active ingredient in Poncho. If seed treatments were the only option, at a minimum I would use a 500 rate but question whether or not the 1250 rate would not provide even better protection under heavy infestations. Keep in mind that with each step up, costs increases as well.

Granular Insecticide:  Granular insecticides are a likely good option assuming you still have granular boxes on your planters these days but there is very little if any hard data specifically on sugarcane beetle efficacy.  My feelings are they would likely be efficacious based on what we know about them but this is still an unknown.  We plan to address this in our research this year.

In-furrow Sprays:  It is estimated that approximately 30-40% of our producers in Mississippi are currently using a starter fertilizer at planting. Many pyrethroids insecticides are labeled to be applied in-furrow and can be successfully mixed with a starter (read labels some may not go into solution very well). We tested Capture LFR (Liquid Fertilizer Ready) at rate of 4 oz. per acre this past year mixed with a starter and were VERY impressed with efficacy on sugarcane beetles.  In fact, it was superior to all seed treatments for control of sugarcane beetles. Here are couple things to remember. Pyrethroid insecticides are not systemic, in other words they will only be where you put them. If you plan on trying this with your starter fertilizer it will be important to actually spray it in the furrow and optimally you would like to “T Band” the spray where it catches a couple inches on the soil surface as well. We accomplished this by turning a flat fan nozzle at a 45 degree angle to the seed furrow. You will not get satisfactory control applying this to the soil surface only or if you dribble your starter or place 2×2.  It is necessary to spray it in-furrow.  If you make the transition to a flat fan nozzle to spray in-furrow, you may find you need to add water with some starters to “thin” them down enough to actually spray out of a nozzle.

Combinations:  Mixtures of available options will offer superior protection and reduce risk if you choose you need additional protection from sugarcane beetles. Here are some thoughts and I will rank in order of efficacy.

1. Seed Treatment + Capture LFR in-furrow. This may not be the absolute best simply because we have not tested every possible combination of options but it is the best we currently know of.  I have been asked if we could leave the seed treatment off and just use the Capture LFR instead.  My opinion is maybe, but the pyrethroid is not systemic and only protects plant parts that are in contact with it.  I would rather do this in addition to a seed treatment and not in place of because we still get systemic activity on pest such as chinch bugs. Another positive of this system is it really does not matter what seed treatment you are using.  The addition of the in-furrow spray will mask any weakness the seed treatments may have on sugarcane beetles so you can choose whatever germplasm you want regardless of the active they put on the seed.
2. Seed Treatment + Granular in-furrow.  This would be my second choice but only because there are a lot of unknowns here. We know that in the absence of sugarcane beetles we have seen yield improvements at times when adding full or half rates of granular insecticides on top of 250 rate seed treatments but little real data exists on efficacy on sugarcane beetles (simply has not been tested). However, if you are not set up to do in-furrow sprays and have granular boxes this would certainly be the next best recommendation and will be superior to seed treatments alone.

Data:  The data slides below are a summary across several trials we conducted in 2012 where we caged 1 male and 1 female sugarcane beetle per plant at the V4 growth stage on seedling corn. Seven days after infestation we removed the pipe and destructively sampled the plants based on a feeding scale we developed to seperate efficacy of treatments on sugarcane beetles. Keep in minde with 2 beetles per plant damage was maximized in these test however, it does give a relative idea of efficacy of various seed treatments.

These are some guidelines and are not intended as a recommendation on every acre. The grower should decide the risk he is willing to assume and make the decision whether or not the extra cost is worth the reduced risk of problems associated with this pest.

Importance of Managing Below Ground Pests EVEN in the Abscence of Sugarcane Beetles:

Remember sugarcane beetles are just one of many below ground pests that make up the soil insect complex in our area.  Often time we see one or several below ground pests causing problems in corn and seed treatmetns and other at planting treatments have proven their worth time and time again. Below are a couple of slides showing yield from trials we had in 2012 IN THE ABSCENCE of sugarcane beetles.