I believe neonicotinoid rice seed treatments are crucial to the survival of our U.S. rice industry. These pest management tools are effective, affordable and minimally disruptive to the environment.
This article is not a comprehensive evaluation, but, I think it does illustrate the importance of neonicotinoids as pest management tools.
CruiserMaxx Rice (active ingredient thiamethoxam) and NipsIt INSIDE (active ingredient clothianidin) are rice seed treatments with neonicotinoid active ingredients. Both products provide effective control of an array of rice insect pests, including rice water weevil (RWW), grape colaspis, chinch bug, aphids and leafhoppers.
The damage/density relationship for RWW in Texas is: 1 larva per core (4 inch diameter X 4 inch deep plug of mud containing 1-3 rice plants) which correlates to about 80lb/acre yield loss. This relationship is linear, so the economic injury level for this pest is about 3 larvae per core. I can sample virtually any unprotected rice field in Texas and find at least this larval density. Thus, preventive rice seed treatments are economical and effective.
Table 1 shows the current treatment thresholds for RWW in Texas. Average yields for Texas are about 7,500 lb/acre, rough rice price is about $12/cwt, and the cost of the neonicotinoid seed treatments is less than $10/acre (given low seeding rates of hybrid and CLEARFIELD varieties which are the predominant varieties in Texas). Therefore, according to Table 1, fewer than 2 larvae per core is the treatment threshold. Again, this shows that preventive seed treatments are economical in light of the general population dynamics of the RWW.
I estimate approximately 40% of Texas rice acreage (about 140,000 acres total) is planted with seed treated with the above neonicotinoids, which shows the importance of this chemistry for our rice farmers.
In addition, these seed treatments are applied at very low rates, particularly relative to hybrid and CLEARFIELD varieties which are predominant genotypes planted in Texas. Basically, Table 2 shows rates of these seed treatments are less than 32g active ingredient/acre. For comparison, in the 1990s, Furadan 3G was the only insecticide available to control RWW—the label rate was 0.5 lb active ingredient/acre = 227 g—7 times more than 32 g.
Table 1. Economic injury levels for RWW (no. larvae per core)
Chinch bug and aphids can be very problematic for Texas rice farmers. These pests attack rice as soon as it emerges from the soil. Severe stand losses forces replanting, which is very expensive and causes farmers to use more water, fertilizer and pesticides. In some cases, farmers cannot ratoon crop because of delayed main crop planting.
These seed treatments are effective insurance against these seedling pests. It only takes a few days for these pests to destroy a rice field. During this time of year in early spring, farmers are busy performing a myriad of agronomic tasks making it extremely difficult to closely monitor fields for these pests. In fact, when I am called to inspect fields with potential chinch bug and aphid problems, the damage has already occurred—the window of opportunity to apply control tactics based on treatment thresholds has closed. Neonicotinoid seed treatments are the answer to this problem.
Table 2. Active ingredient/acre
Texas does not have problems with grape colaspis. However Arkansas, Mississippi and Missouri rice farmers plant significant rice acreage with seed treated with the neonicotinoids to control this pest that attacks seedling rice. Please contact Gus Lorenz (University of Arkansas), Jeff Gore (Mississippi State University) and Moneen Jones (University of Missouri) for their input.
Why Rice Producers Need Neonicotinoids
Rice planting operations in the South are very different from soybean planting operations in the Midwest. Rice farmers do not add a lubricant to the planting box. So, the neonicotinoid seed treatment applied to rice stays on the seed and does not disperse from the planting box. This is a very important distinction between rice and soybean planting operations.
- Valuable environmental benefits are provided with rice seed treatments.
- Minimize drift to non-target areas and organisms (including bees, pesticide handlers and farm workers)
- Reduce fuel costs in terms of aerial applications
- Extremely low rates of active ingredient
- Early control of target insects can result in fewer pesticide applications Neonicotinoids represent another class of chemistry which can help delay development of resistance
- Less contamination of flood water since seed treatments are not directly applied to water
- Possibly less chance of pesticide residue in grain because of the earliness of application.
As an aside, last year I spoke with a beekeeper who overwinters his honeybees on the margins of rice fields in Liberty County, California where goldenrod, other compositae and Chinese tallow trees grow in abundance. He remarked he has never suffered any bee kills from the nearby rice fields and added this overwintering habitat is essential to his business which includes many agricultural endeavors in California.