Friday, May 17, 2024

Aquatic insects in rice

Rice Research Entomologist

In rice fields, many insects are aquatic and obtain oxygen by absorbing this dissolved gas directly from the water through their integument, by surfacing and taking a bubble of air with them underwater or by trapping air among fine hairs on the undersides of their abdomens.

Speaking of aquatic insects, I am frequently asked by farmers and crop consultants about egg masses found on leaves of rice under flood. The eggs in these masses are brown/grey/black/green/white (depending on age), elongate and spindle-shaped. A single mass can have many overlapping eggs somewhat resembling a sugarcane borer egg mass.

Not to worry about your rice crop; these masses are eggs of biting deer flies! Female flies need mammal blood, such as humans and cattle, to produce eggs, which are laid on rice foliage. Eggs hatch, and the worm-like larvae fall to the water below and begin their aquatic existence. The larvae are dark-colored, flattened, leathery and feed on detritus – so they do not pose a threat to our rice crop.

Another aquatic insect I am asked about is the immature dragonfly, which is an excellent hunter. It has retractable/extendable mouthparts that help it capture all kinds of aquatic invertebrates and even small fish. Before it transforms to an adult dragonfly, the immature insect climbs up above the water surface on a rice culm. The adult then escapes from the immature exoskeleton leaving behind the white cast skin of the immature clinging to the culm.

In addition, you have probably observed swarms of “gnats” in the shape of an inverted pyramid hovering above stagnant bodies of water (in drain ditches, for instance) in the early spring. Usually you will see these swarms at dusk. The swarms are composed of adults of rice seed midges – small flies whose larval stages can be damaging to water-seeded rice. The larvae feed on germinating rice seed underwater. To minimize rice seed midge injury, employ a pinpoint instead of a continuous flood, pre-sprout seed, plant as soon as possible after flooding and possibly increase seeding rate.

We have many good rice insect pest management tools, including seed treatments containing an array of active ingredients and foliar-applied insecticides representing different classes of insecticides. If you have insect questions, contact your state research/Extension scientists – or you can always contact me: (409) 658-2186 or

Good luck this field season!

Pest management


When I got into this business, management of the rice water weevil was limited to two practices: Apply carbofuran (Furadan) or drain the field. Managing rice stink bugs has not changed in terms of techniques; however, the materials at our disposal have changed.

Today we can control the rice water weevil preventatively by treating seeds with Dermacor X-100, CruiserMaxx or Nipsit INSIDE insecticides. All three are effective against the rice water weevil. In addition to controlling the rice water weevil, Dermacor controls or suppresses the Mexican rice borer, sugarcane borer, rice stalk borer and fall armyworm. CruiserMaxx and Nipsit INSIDE pick up Colaspis beetles, chinch bugs and thrips. CruiserMaxx also includes a fungicide package to control seedling diseases. A mixture of Dermacor with either of the other insecticides will widen the spectrum of insect control, but labels must be consulted and followed carefully, or control will be compromised.

Nipsit INSIDE and CruiserMaxx can only be used on dryseeded rice. Dermacor can be used on water-seeded rice in areas where the Mexican rice borer is of concern. Dermacor-treated seed cannot be soaked; it must be dry seed. All of the seed treatments must be applied by certified seed treaters.

If seed treatments are not used, the next line of defense are the foliar insecticides, which, until this year, were all pyrethroids (Declare, Fastac, Karate, Mustang Max and Prolex). Belay is a new foliar (neonicotinoid) insecticide. It is used in the same manner as the others in that treatment is recommended when rice water weevils or leaf scarring is found and water is present in the field. Trebon is a granular insecticide applied at about the same timing and is of a similar chemistry to the pyrethroids.

Given the complaints about pecky rice in years when stink bug pressure is heavy, I am fairly confident that our current threshold values for rice stink bug are correct, but we will see what Dr. Mike Stout’s research results provide. This will be the last year for use of methyl parathion. Methyl parathion cannot be sold after Aug. 31, 2013, and cannot be used after Dec. 31, 2013.

Another change on managing rice stink bug for Louisiana is the discontinuance of recommending malathion. Studies by Dr. Stout have confirmed what we have seen in the field for the past few years: Malathion does not control rice stink bugs anymore. Tenchu insecticide, a neonicotinoid, has been granted a full federal label for use to control rice stink bug in Louisiana in 2013.

All of this information is available through your local county Extension agent.

Don’t cut rates

Rice Extension Agronomist
University of Arkansas,
Division of Agriculture

As we begin to finalize plans for rice acreage in the coming weeks, it’s important to look back at what we did last year. I have had more than one discussion with farmers about certain fields performing poorly last season with no particular reason why.

Upon further discussion, it was revealed that these poor-yielding fields were planted to soybean the previous season and treated with Prefix or Flexstar. These products, along with several others, have a 10-month plant-back restriction for rice. Simply put, be conscious of the previous year’s herbicide program when rotating into rice.

According to Dr. Bob Scott, Extension weed scientist, it will be important to focus on utilizing multiple modes of action in Clearfield rice. We cannot afford to depend solely upon a single mode of action (MOA) for weed control. (For example, Newpath and Beyond are the same MOA).

Begin with a burndown application, if needed, followed by a pre-emergence application (e.g. Command + Facet). Remember that it may be necessary to flush to activate pre-emergence herbicide applications. Please keep in mind that we are beginning to have problems with barnyardgrass in rice.

Populations of this weed have been found to be resistant to propanil, Facet, Command (limited) and ALS (i.e. Newpath, Beyond, Regiment, Grasp). Barnyardgrass could become “the pigweed of rice.” Resistance to Prowl, Bolero and RiceStar/Clincher has not been found, but it is becoming increasingly important to protect these remaining modes of action as no new herbicides are coming any time soon.

We saw a decrease in the percent of acreage planted to Clearfield rice in 2012. In terms of managing our available weed control options, both Dr. Scott and I view this as a step in the right direction. Given instances of ALS-resistant barnyardgrass, we must limit ourselves to using Clearfield technology only where we need it, when we need it.

If ALS-resistant barnyardgrass were to develop in a field where you need this technology for red rice control, how long can you justify continued use of this technology when you will need additional herbicides to control barnyardgrass alone?

My guess is not long.

Early season insect control in rice continues to improve as we now have three insecticide seed treatment options available for 2013. Growers have the option of having their seed treated with CruiserMaxx Rice, Nipsit INSIDE or Dermacor X-100.

Grape colaspis is typically the most worrisome of early season insect pests in rice.

CruiserMaxx Rice and Nipsit INSIDE both provide excellent control of this pest.

If rice water weevil is typically your greatest problem, Dermacor X-100 may be your best bet. However, all three of these products have activity on both grape colaspis and rice water weevil. Ultimately, choose the one that fits your insect problems and your budget.

Choose the one offered at the lowest price, but don’t cut the rate.

Keep in mind when evaluating price that CruiserMaxx Rice contains both an insecticide and a fungicide, while Nipsit INSIDE and Dermacor X-100 are insecticides only.

Final reminders: For early season weed control, don’t get behind to start the season. Flush in a pre-emergence herbicide and use multiple modes of action. Don’t wait until weeds are large before spraying.

For early season insect control, ensure your seed is treated properly with good seed coverage and don’t cut rates.

ID specific problems

Agronomy Specialist

Missouri producers are telling us that their attention is on selection of varieties, early control of resistant and other weeds along with early insect and disease control.

We confirmed the value of flushing early and often in 2012 for herbicide activation, which resulted in good early weed control. Due to the drought, we were forced to flush early and often for rice seed germination. With conventional and Clearfield rice, we recommend starting clean with tillage or a burndown, followed with a pre/delayed pre, early post herbicide program.

We estimate that Missouri farmers plant about 50 percent Clearfield technology. We suggest matching technology and mode of action to your specific weed problems. And, plan and pay attention to not only what your neighbor is planting in the field next to yours but to all applicators in the area throughout the season. My work on drift and misapplications tells me how complicated it is, so that’s why I’m emphasizing to plan carefully now.

For early insect control, we are following the insecticide seed treatment recommendations of entomologist Dr. Gus Lorenz, University of Arkansas Division of Agriculture. Due to the low seeding rates and cost of seed, it’s very important to control seedling diseases and insects. The best way to get seedlings off to a healthy start is seed treatments matched to your insect and disease situation.

Missouri producers ended the 2012 season with a good-yielding rice crop. For 2013, we suggest they identify their specific problems for each field, study their options for solutions and build a plan to match the technology to get positive results. We recommend enlisting the help of a consultant, your retailer and university personnel. I know it’s not simple. That’s why God made a farmer.


‘Living fossils’ that are too common

Department of Entomology

Tadpole shrimp (TPS), Triops longicaudatus, is a crustacean and a common problem of seedling rice in California. Most fossils are rare, but species in this group are often referred to as “living fossils” because their morphology has remained unchanged for over 180 million years. Tadpole shrimp feed on germinating rice seeds, killing them and reducing the stand. Their digging during egg laying and foraging can uproot young seedlings, which float and accumulate to the sides of the basin, especially downwind. Additionally, TPS digging muddies the water, reducing sunlight penetration, which in turn reduces seedling growth. TPS do not pose a threat to rice seedlings once they are rooted and emerge through the water. At this time, seedlings are large enough not to be affected.

Copper sulfate has been the primary control method for TPS and algae from the 1990s until recent years. Research has shown that rice straw can bind up to 75 percent of a copper treatment, making it less available in the water. Since 2001, air quality regulations limit the amount of straw California growers can burn, and this has increased the straw residue present in fields. Pyrethroids, registered for rice water weevil, are now the best chemical management tool, although the application timing for TPS is earlier than for rice water weevil.

Cultural control, including minimizing the time from the start of flooding to getting a stand established, is the best management tool. Quickly flooding fields, seeding with well-prepared seed, flying on seed as soon as possible after flooding, optimal water depths, etc. are also important factors. This allows the rice seedling to root and establish before the TPS can hatch and obtain the most damaging stage. In monitoring for this pest, look for muddy water in the absence of significant wind, a high number of floating seedlings, the floating caste skins from the TPS molts, etc. Let’s hope for great weather during this season’s rice seeding so we can fend off this “prehistoric” creature. Even though it hasn’t changed for 180 million years, TPS still competes very efficiently with us for rice stands.

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