California
Larry Godfrey
Editor's note: Larry Godfrey is an Extension entomologist in the University of California, Davis,
Department of Entomology.
Rice water weevil is annually the most economically important insect pest of California
rice. Management schemes for this important pest changed in 1999, shifting from a pre-plant
incorporated insecticide strategy (Furadan 5G) to applications of post-flood insecticides.
Dimilin 2L and Warrior were registered for rice water weevil management in California in
early 1999. To optimize control, these treatments should be applied soon after rice emergence
(two- to three-leaf stage) but before rice water weevil adults have deposited a significant number
of eggs. Refining application timing and learning how to best use these products in the California
system is a challenge for the 2000 rice season.
But substantial progress was made in this regard in 1999.
University of Callifornia, Davis, rice home page
UC Statewide IPM Project
Arkansas
Nathan Slaton
Insects are usually not one of the primary pest concerns for Arkansas rice growers when
compared to weeds and diseases. However, some fields have a history of "insect" problems. The
grape colaspis or lespedeza worm has been one of the toughest to manage since we have lacked
effective means of scouting and treating for the insect.
Damage occurs below the soil surface in dry-seeded fields during the seedling stage before
flooding. Visible symptoms of damage include yellowing of leaves and dying or "withering" plants
especially during hot, dry conditions. Damage from this insect is often blamed on salinity, seedling
disease or both since the damage is below ground and the tiny larvae is not easy to find. Flushing
often improves the situation but may not be enough to prevent significant stand loss in cases of
heavy infestation and severe damage.
Research conducted in grower fields during 1999 showed that Icon insecticide seed
treatment prevents damage. Dr. John Bernhardt established tests in four grower fields in 1999 to
evaluate Icon seed treatment for efficacy on grape colaspis. Damage from grape colaspis was
found in two of the four fields but only where untreated seed was planted.
Seedlings in areas that were planted with Icon-treated seed had no visible signs of damage
or stand loss. To the row, damage ended where untreated seed use ended and use of Icon-treated
seed started. Icon seed treatment will also control rice water weevil larvae, rice stalk borer, and
seed midge or bloodworms in water-seeded fields.
Damage from all of the insects mentioned affects only a very small percentage of the
Arkansas rice acreage. But when damage occurs, it can reduce yields and/or increase production
costs associated with rice management practices. Use of Icon to control these pests will need to
be made on a field-to-field basis, with those fields having a history of previous damage being ideal
candidates for use of Icon-treated seed.
The decision to use Icon-treated seed (or not) to control these pests must be made before
damage occurs since this is a preventative use of insecticide. Growers will have to make an early
economic decision between the potential benefits of Icon to production practices and the
increased cost of the seed treatment which is about $ 12-$15 per acre.
University of Arkansas Cooperative Extension Rice
Louisiana
Johnny Saichuk
Last year presented a great deal of uncertainty for rice growers who had become
accustomed to managing the rice water weevil with carbofuran (Furadan). Farmers were allowed
to use the last remaining supplies in stock rather than create an environmental hazard through
disposal procedures. But the Environmental Protection Agency warned that growers would no
have no more carbofuran use as a rice water weevil control material.
In 1999, growers used fipronil-(Icon) treated seed, lambda-cyhalothrin (Karate Z) or
drained their fields to reduce water weevil injury. Diflubenzuron (Dimilin) received a label late in
the season and saw very limited use. This year, the choices are the same.
Icon proved to be very effective, but deciding whether to use it must be made before
purchasing seed because it is market only as a seed treatment. Label changes are expected with
this product for 2000.
Timing of Karate for management of rice water weevil is crucial. The change from
scouting for a specific number of adult weevils in 1998 to treating when adults were present and
conditions were right for oviposition in 1999 proved to be a good recommendation for growers.
Most reports of use in commercial fields were good. A number of questions have been raised
about combining Karate with pre-flood herbicide applications. At this time the LSU Ag Center's
scientists are investigating thet possibility, but no recommendation has been developed.
Dimilin may get some exposure this year in commercial fields. Dimilin kills the eggs of rice
water weevils, not adults or larvae. It should be applied to fields only after permanent flood is
established and if adults are present.
For details on the use of these materials, always read the product label. Contact your local
county agricultural Extension agent for additional information.
Louisiana State University's Ag Center Rice page, Insect topics
Texas
Arlen Klosterboer
Texas rice farmers were able to apply Dimilin 2L, Icon 6.2FS and Karate 1EC for rice
water weevil control in 1999. Existing stocks of Furadan 3G were also applied in 1999, but
Furadan 3G will not be available in 2000.In 1999, about 25 percent of Texas rice acreage was
planted with Icon 6.2FS-treated seed.
Research conducted by M.O. Way from Texas shows that Icon 6.2FS also controls chinch
bugs and leafhoppers/sharpshooters. Stemborers (sugarcane borer and Mexican rice borer) also
were controlled in research plots in 1999 with a high rate of Icon 6.2FS-treated seed.
Karate Z also provided good control of rice water weevil in 1000. Other insects controlled
were aphids, chinch bugs, fall armyworm, grasshoppers and stink bugs. Texas data show that
Karate Z can be tank-mixed with common rice herbicides and applied just before permanent flood
with no phytotoxicity problems.
Dimilin 2L was applied on limited acreage in Texas in 1999. It provides good control of
rice water weevil when applied early post flood. Remember all of these insecticides can be toxic
to crayfish, so don't allow them to directly contaminate crawfish ponds.
If southeast Texas experiences another mild winter, farmers can expect severe insect
problems next season. Stem borer damage seems to be increasing, particularly in Matagorda,
Jackson and Ford Bend counties. Also, stem borers appear to be an increasing problem on ratoon
rice. Careful and frequent scouting for insect pests is absolutely crucial for effective and
economical management.
Texas A&M Cooperative Extension Crop & Soil Science page
Joe Street
Mississippi
I know it's early to be thinking about rice water weevils, but it's time to think about treating seed
with Icon for the pest's control. If you have a history of water weevil damage on your farm, you
can expect to have them in 2000.
Icon can be applied only by an authorized seed dealer, so it's a good idea to order seed
early for treatment. Icon has done an excellent job of controlling rice water weevils and it reduces
the need for scouting for adults.
Other options include Dimilin and Karate Z for controlling the adult water weevils just
after permanent flood establishment. Whether or not you use Icon, you need a good fungicide
seed treatment especially if you intend to plant early during cooler weather.
With excellent dry weather during the 1999 fall, much precision land leveling was
accomplished. Soil fertility is generally one of the limiting factors in good rice production on the
recently leveled fields. There is almost always some nutrient deficiency in the cut areas.
The most common deficiency I observed last year was phosphorus, which can definitely
limit yields. Only soil analysis reveals the true nutrient needs of the field. Grid sampling and
variable-rate application tech ology can be used to get the needed nutrient on the correct portion
of the field. It's much better to correct the nutrient problem before planting than after symptoms
occur in the crop.
Mississippi State University Extension Rice page
