This is the first time since I moved to California that I've seen leafhoppers actually injuring rice. Leaf tips turned yellow, and from the road it looks like salt injury, but once you get in the field you can see leafhopper nymphs and adults jumping and flying around.
What we have is aster leafhopper. They are reported to feed on broadleaf weeds and rice. I have some research plots in this field, with some areas where rice was not planted between plots. Weeds grew on the open areas, and after a propanil application that killed the weeds the leafhoppers might have moved to the rice.
From the UC IPM: Rice website: "Although leafhoppers can be present in fields during most of the growing season, the heaviest populations usually occur from early July through mid-August. Leafhoppers feed on rice plants by sucking up plant fluids through their long, piercing mouthparts. Although they are not known to vector of any rice pathogens in California, leafhoppers may occasionally occur in sufficient numbers to cause damage by their feeding. Injury associated with leafhoppers include stippling, yellowing, and drying leaves. Leafhoppers prefer senescing leaves, and symptoms usually occur on older leaves first. Leafhoppers are very mobile; adults fly and nymphs jump. Thus, infestations are rarely localized but appear generally throughout the field."
We haven't treated this field yet. There are still plenty of leafhoppers, but the plants are growing fast and putting out new leaves. If the leafhoppers remain and start injuring the flag leaf, a treatment might be appropriate.
I've been getting calls about sedge surviving propanil applications. Last year, research conducted by Albert Fischer showed that there are populations of smallflower umbrellasedge that are truly resistant to propanil (read the article here). However, just because sedge was not controlled by propanil, it doesn't mean it is resistant. Some other explanations for lack of control are:
- Propanil was applied too late. The older the weeds, the harder they are to kill.
- The rice canopy was large and shielded the weed during the application.
- Water level was too high and weeds were not exposed.
- Incompatibilities in the tank mix.
- Dosification errors.
- Equipment failure.
If you suspect you have propanil-resistant sedge in your field, the UC Rice Weed Project can test seed from the suspected weeds and confirm or rule out resistance. Collect a seed sample, fill out the Resistant Weed Seed Testing form (download it here), and send or drop off the sample at the Rice Experiment Station in Biggs. The testing is conducted early in the spring and the results made available to you ahead of seeding.
A few weeks ago I was on the phone with a grower worried that he had put too much nitrogen on his rice for the cool year we were having. Then, the weather turned and got really hot. So, are we in a cool or warm year? What is the trend so far? It is hard to come with an answer just by comparing the daily average temperatures for this year to the historical average temperatures.
A way to discern what is going on is to look at the amount of heat units or degree days (DD) accumulate so far. Using the Colusa CIMIS station and a lower developmental threshold of 55oF, I calculated how many DD we have accumulated since May 1st.
Looks like 2013 is on the warmer side. The year 2011 was a characteristically mild year, while 2012 was closer to the historical average.
When looking at May and June individually, you realize that most of the extra DD were accumulated in June. May was closer to 2012 and to the historical average.
What are some of the implications of this? Early planted fields are already pass PI. Fields that have not reached PI yet should be evaluated for nitrogen topdress need. Warmer conditions promote growth and nitrogen use, and you don't want your crop to run out of fuel before the end of the race.
We've seen that during mild years blast can become a problem in some areas. Warmer temperatures seem to discourage explosions of the disease. If you are considering a treatment, scout your fields to identify infections and talk to your neighbors to see what is happening in the area.
The 2013 Rice Production Workshop will be held on July 25 at the Lundberg Family Farms Multi-Purpose Room, 5311 Midway, Richvale, CA. The Workshop, organized by University of California Cooperative Extension (UCCE), will present current and potential growers, pest control advisers, industry representatives, regulatory agencies and other interested parties with a broad view of the California rice production system and the most up-to date research findings. Information will be presented by UC Davis and UCCE scientists and extension personnel with many years experience working in California rice.
Prepaid enrollment ($75) is required, and enrollment is limited to 75 people. Please enroll by July 21st to ensure your participation. Seats will be filled on a first-come basis. The registration fee covers a light breakfast, lunch and workshop educational materials.
Enroll on-line at http://ucanr.edu/2013riceworkshop.
- Author: Tunyalee A. Martin
It’s that time of year again when hot weather fuels the creation of ozone, or smog. Some pesticides emit volatile organic compounds (VOCs) that contribute to ozone formation. Using pesticides that release VOCs may be restricted in certain California locations between May 1 and October 31.
If you plan to apply a pesticide, use the Department of Pesticide Regulation’s VOC calculators to determine emissions from fumigant and nonfumigant pesticides. Get there by clicking on the Air Quality button at the top of each treatment table in the UC IPM Pest Management Guidelines: Rice.
Simple steps can minimize the release of VOCs into the air:
- Use pesticides only when necessary.
- Decrease the amount of pesticide applied if appropriate.
- Choose low-emission management methods.
- Avoid emulsifiable concentrate (EC) formulations and fumigants.
Ozone, or smog, is caused by mixing VOCs, nitrogen oxide, and sunshine. High levels of ozone can harm people and crops. Regions in California that do not meet federal or state air quality standards for ozone, called nonattainment areas, may restrict the use of pesticides that release VOCs.