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17
Mar
2011
Rice Insecticide Seed Treatments
Author: Gus Lorenz, Extension Entomologist

As the costs of crop production increase, growers have to spend their money wisely and choose correctly on their inputs to maintain profitability. With the increasing “front loaded” input costs of fertilizer and seed, growers are spending a much higher percentage of their crop budget before they ever see a plant emerge in the field. So, an insecticide seed treatment (IST) compounds that situation even more. That’s why we get the question from growers and consultants: “Are these ISTs really worth the money?”

The Extension Entomology program became interested with ISTs after the loss of Icon (fipronil) seed treatment whose label was voluntarily withdrawn by the company.  Rice growers were then left with very few options for control of the major insect pests of rice including the grape colaspis (GC), Colaspis brunnea, referred to by many growers as the “lespedeza worm” and the rice water weevil, Lissorhopterus oryzae. Both of these pests have the potential to substantially reduce plant stand and subsequently yield in any given year.

Seed Treatments Currently Available

Cruiser® 5FS (Syngenta Crop Protection) and Dermacor® X-100 (DuPont) were granted full labels for use during the spring of 2010 in the U.S. Prior to 2010, an extensive testing program was conducted through Experimental Use Permits. In 2008, Arkansas received a Section 18 with Louisiana and Mississippi for Dermacor and we were able to observe the product in large block trials. In 2009, Dermacor received a full label. In 2009, Arkansas was the only state granted a Section 18 for Cruiser and we were able to compare it to Dermacor and untreated checks in several locations across the rice growing area of the state in large and small plot trials. Since 2007, we have been able to conduct over 100 small and large block trials with these products and the comments on these seed treatments herein, are based on these observations. In 2011, a third seed treatment, NipSit Inside (Valent Corporation) will be available on limited acreage. An EUP was granted on 40,000 acres of which 20,000 is allotted in Arkansas. We have had the opportunity to evaluate this product in small plots but look forward to seeing it on grower fields across the state. This will provide us a good opportunity to evaluate the product on large plot trials in the state.

Experiments and demonstrations were conducted from 2007 to 2010 on numerous grower fields across the state and the Pine Tree Experiment Station, Colt, Ark.  These trials consisted of small plot replicated experiments and large plot demonstration trials. In these trials we have used seeding rates ranging from 20 lb/ A to 120 lb/ A. We have observed these seed treatments on conventional, Clearfield and Hybrid types of rice. The selection of locations for our trials is based on fields with a history of problems with either grape colaspis or rice water weevil. However, keep in mind, we did not experience insect problems in every field.

Observations on Seed Treatments

Plant Health

Throughout the testing of these seed treatments we have seen a general trend to improve stand count and vigor in many fields with the use of seed treatments. Seed treatments have increased stand counts in many trials as much as 10-20% above the untreated check. We have also documented increased plant height in some fields. Let’s be real clear here, we do not see these differences every time. The amount of vigor seen may be dependent on many factors including pest pressure, environmental conditions, seed quality, etc.  Many times we have observed, under stressful conditions, the seed treatment helped to moderate or buffer stress. So, the value, in some cases, may be more than just insect control. We base that statement on studies with these seed treatments in the field as well as the greenhouse. Under the controlled environment situation of the greenhouse, we were also able to see quicker emergence and increased plant height, again, not every time but certainly often enough for us to see that differences can be observed.

Insect Control

Our trials indicate that all three of these products, Cruiser, Dermacor and NipSit Inside, all provide good control of rice water weevil.  Overall, it is safe to say that Dermacor has an edge on Cruiser and NipSit Inside on control of rice water weevil. Studies in Mississippi indicate that when populations exceed 20 weevils per core that Dermacor provides better control than Cruiser; however, control with Cruiser has been acceptable. The same can be said here in Arkansas. Based on our studies with grape colaspis, or “lespedeza worm,” Cruiser and NipSit Inside have an edge on Dermacor. In 2009, when we had the Section 18 for Dermacor, we did observe that Dermacor provided suppression of grape colaspis, but in severe infestations, stand loss did occur in a few grower fields.

Based on our studies all of these products provide enough control of these pests to avoid major problems.

Yield

Plant vigor and insect control is good but obviously the bottom line is yield. Do the ISTs provide the grower with value? All of these seed treatments in our observations show a significant benefit in terms of yield. Over a three year period, with Cruiser we have seen an average increase of 6 bushels per acre above the untreated check 73% of the time. With Dermacor an average yield increase of 6 bushels per acre 75% of the time and a 5 bushel yield increase with NipSit Inside 75% of the time.  As you can see these numbers are very comparable and indicate that no one product is better than the other, that in fact, they all provide a good return on investment. In similar trials conducted in Mississippi, Dermacor provided an 11.8 bushel/acre yield increase with a 72% probability of return while Cruiser provided an 8.3 bushel per acre yield increase 79% of the time.  This consistency in value should give the grower the confidence that these products work.

Based on these results, insecticidal seed treatments are recommended for rice water weevil control in Arkansas.  Cruiser and NipSit Inside are recommended for grape colaspis control and Dermacor for suppression of grape colaspis.

Considerations for Use of ISTs in Rice

Growers should consider seed treatments in the following situations:

  1. Planting high value seed or planting low seeding rates;
  2. Planting under less than optimum conditions: early planting, no-till, marginal seed quality;
  3. Known problem fields, history of grape colaspis or rice water weevil;
  4. Planting varieties of seed with poor vigor;
  5. Late with burndown;
  6. Field yield potential- if potential is low, added costs may not be advisable.

Try to choose the seed treatment that you want, not what a company wants you to use. If you are still leary, try it yourself, these ISTs are expensive and you need to be comfortable making this decision. Beware of cutting the rate, these products are very rate responsive, if you start cutting the rate you may not see the same advantages we have, in fact we have already done that and find that lower than label rates just don’t work. Most of the product rates currently used were based on the work we have done right here in Arkansas.

Bottom Line

These ISTs can provide you protection from our major rice pests, they protect your investment, and they maintain yield potential for you. We strongly recommend the use of these products and we will continue to conduct research on these products and any other products that may be developed to continue providing you with recommendations that help your bottom line.


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