In the past three years, there has been an increase in the number of reports of damage to rice by rice seed midge in the Sacramento Valley. During 2021 and 2022, the issue was not widespread, but there were some instances where the damage was severe. In 2023, several reports of damaged fields were received. We visited several of these fields with varying levels of injury in Colusa and Glenn Counties. One of these fields lost almost 20 acres to midge. Some of the damaged fields had received a pyrethroid treatment soon after seeding. While these insecticide applications may have provided some control in the past, it appears that may no longer be the case, and we are puzzled by the apparent inefficacy of the insecticide.
Rice seed midge survive in canals and ditches year-round. During spring, adults swarm, mate, and lay eggs on the surface of the water as fields are flooded. Eggs hatch after two days, and very small larvae swim to the bottom where they feed and build silken tubes that they use for protection. The tubes get covered with mud and algae and are easy to spot when the water is clear. The larvae initially feed on diatoms and algae and can start feeding on rice seeds and seedlings after around 5 days. After a few more days, larvae pupate, turn into adults, and repeat the cycle again.
Rice seed midge tubes near injured seeds
Injured seed with rice seed midge larva
When feeding on the germinating seed, larvae consume the embryo and endosperm, hollowing them out. Damaged seeds show an entrance hole in the hull near the embryo. Midge larvae can also clip the developing coleoptile or radicle, causing injury similar to tadpole shrimp. Hollowing of the seed and clipping the germinating structures will kill the seed. Once the coleoptile and radicle are well developed, midge injury is less likely to kill the seedling. Midge larvae also feed on larger seedlings. It is not uncommon for midges to perforate leaves; they may even attach their silken tubes to the seedling.
However, this type of injury does not kill the seedling. The best strategy to reduce the risk of injury by rice seed midge is to avoid planting too early or too late, avoid low or high temperatures during seeding, and seed soon after flooding. If injury is detected early enough and the field can be drained quickly, draining the field can reduce damage; however, injury can still occur in low areas of the field that do not drain completely. Planting high quality seed and maintaining an adequate flood can help seedlings establish quickly and avoid midge injury.
Lambda cyhalothrin, a common pyrethroid insecticide used for seedling pests in rice, has been used to manage rice seed midge. However, in recent years, we have noticed that some treated fields are still damaged by the midge. There is some evidence that indicates that midge larvae may not be as susceptible to this insecticide as we thought, possibly due to repeated applications of these insecticides through time. We are conducting field studies to confirm these observations and determine which insecticides could be used to help manage midge.
Last year roughly half of the rice acreage was left fallow. We have been conducting research (funded by the Rice Research Board) looking at the differences between rice grown after a fallow versus rice grown following rice. We have found that rice following a fallow has higher yield potential. In our two years of study we saw about a 2 to 3 sack yield advantage in rice after a fallow. Higher yields may be due to reduced disease incidence. In both years of the study we saw lower incidence of stem rot in rice following a fallow year. As mentioned, this can lead to higher yields but also to less lodging.
Regarding nitrogen management, we used a labeled nitrogen fertilizer to allow us to determine if the nitrogen in the plant came from fertilizer or from the soil. We found that fertilizer N was used similarly when rice followed a fallow or when it followed rice. Interestingly, we also found that when rice followed fallow, more nitrogen was available from the soil – particularly after PI. This has a couple of implications. First, it means if you had a fallow rice field last year, you may be able to back off on your overall N rate. In our data from one year, we found that you could back off by up 20 to 30 lb N/ac. Secondly, most of the additional N availability came after PI. This suggests that if you are routinely topdressing, it may not be necessary when rice is following a fallow year. Regardless, I would still suggest monitoring the crop at PI using a Leaf Color Chart or a GreenSeeker to make a more informed decision about N management.
Some of you may be asking “why do we get more nitrogen in a field that was fallowed?”. This is a great question. In fields that have been in rice where the rice straw is incorporated and flooded during the winter, phenols accumulate. Phenols are an organic compound that tend to build up when organic matter, such as straw, decomposes under anaerobic conditions. Given how most farmers manage their straw we would expect a build up of phenols. In fact, we have looked at soils around the valley and have found this to be the case. Phenols also bind nitrogen, making it unavailable for plants. Imposing long periods of time when the soil is aerobic such as during a fallow period, promotes the breakdown of these phenols and the release of nitrogen.
As I write in late March, no one is out in the fields yet. It is too wet. This suggests that planting will be later than normal. On a positive note, I did see that NOAA has forecast a drier than normal April. Anyways, with this I would like to suggest some thoughts for planning.
First, from our Yield Contest data, we have seen that it is really important to ensure good stand establishment. In late years, it is easy to get in a rush and skip steps. While this may be necessary, make sure you do your best to get a good stand. You want an evenly spaced 25 established plants per square foot.
Second, a late planting will probably mean a later harvest. With late harvests, one risks fall rains which can further delay harvest and reduce grain quality. On your late fields, think about planting earlier maturing varieties such as M105, M-206 and M-210. These varieties have good yield potential but are about 5-7 days earlier (more in the southern part of valley) the M-209 or M-211. These longer duration varieties should be planted in earlier fields if possible.
Third, do not over fertilize with nitrogen as this can further delay harvest. For more on this, see the other topic I have written on for this newsletter.
- Author: Whitney Brim-DeForest
Following is a brief outline of the Rice Field Day program:
7:30 - 8:30 a.m. REGISTRATION AND POSTER VIEWING
8:30 - 9:15 a.m. GENERAL SESSION
• CCRRF Annual Membership Meeting
• Rice Research Trust Report
• California Rice Industry Award
9:30 - Noon FIELD TOURS OF RICE RESEARCH
• Variety Improvement
• Disease Resistance
• Insects and Control
• Weeds and Control
Noon LUNCHEON CONCLUDES PROGRAM
Lunch will be served in the New Research Building with seating at the tables on the lawns under the canopies. The program will begin at 8:30 a.m. with a General Session that serves as the Annual CCRRF Membership Meeting. Posters and demonstrations will be in place during registration until after lunch. Field tours of research will emphasize progress in rice variety improvement, disease, insect, and weed control. The program will conclude at noon with a lunch that includes rice.
We hope to see you on August 31st. The RES is located at 955 Butte City Highway (Hwy. 162), approximately two- and one-half miles west of Highway 99 north of Biggs, California.
- Author: Whitney Brim-DeForest
|EVENT:||UC Rice Pest Management Course 2021|
|DAY/DATE:||Friday, Sept. 10, 2021|
|LOCATION:||Hamilton Road Field (on West Hamilton Rd. between Hwy. 99 and Riceton Hwy., Biggs, CA)|
|EVENT TIME:||8:00 AM-3:25 PM (Check-in: 7:30-8:00 AM)|
|COST:||Non-student: $80/100; current student: $40/50|
This year will mark the 4th rice-specific course at the Hamilton Road Field and the Rice Experiment Station in Biggs, CA. The UC Rice Pest Management Course 2021 will begin with an interactive field tour of the research plots (Hamilton Road Field) where attendees can get up close to the weeds and rice (BRING YOUR BOOTS!) The course will include hands-on weed identification sessions on emerging and mature weeds and a disease and pest ID session. In the afternoon, speakers will address several pertinent topics in CA rice, including regulatory updates, new herbicides for resistance management, diseases and pests research updates, and how to construct a weed management program.
The course is a collaborative effort between UC Cooperative Extension (UCCE), UC Davis, and the California Rice Experiment Station (CRES.) “This course provides a strong foundation for weed and pest management in California rice, as well as a chance for interaction and discussion with researchers on the latest pests and pest control options for California rice systems” said Whitney Brim-DeForest, UCCE Rice Farm Advisor. The event is a great opportunity for pest control advisers, growers, industry, extension, and interested students to gain a deeper understanding of pest management topics that affect rice.
Enrollment is limited, so register early. The cost is $80 if received by 9/7/2021 and $100 if received after 9/7/2021 (if there is space.) The cost for current students with proof of student status is $40/$50. Online registration closes on 9/7/2021. If there is space, you can register onsite the day of the event. For more details or to register, visit http://wric.ucdavis.edu and click on RICE PEST MANAGEMENT COURSE.
CA DPR and CCA continuing education units pending approval.
If you have questions, contact Whitney Brim-DeForest [firstname.lastname@example.org or (530) 822-7515.]