Will cold and rainy weather impact seed treatments in corn and rice?
This is an important question right now with the weather conditions that we have had over the last few weeks. A considerable amount of corn and a little bit of rice has been planted over the last 3 to 4 weeks. In most of those fields, the crop has either just emerged or has not emerged yet. There is some reason to be concerned about delayed emergence and the impact it will have on insecticide seed treatments because the clock starts ticking when the seed goes in the ground.
Cold temperature, in and of itself, is probably not a big concern, even with the delayed emergence that it causes. The cold temperature will slow the metabolism of the insecticides in plant tissues and also slow any breakdown that occurs in the soil. All of the rain that we have had over the last couple of weeks combined with cold temperatures could potentially have had a negative impact, especially where the soils have remained saturated for a long period of time. In saturated soils, the insecticide can become diluted in the soil and may even be washed out of the root zone.
The good news is that the insecticide begins moving into the seed as soon as it begins to imbibe water. We probably haven’t had a complete loss of the seed treatment, but the saturated soils probably did have an impact. The question is whether or not it had enough of an impact to compromise efficacy and that is something that we don’t know at this point. The best thing to do is keep a close eye on the crop and take appropriate measures if you suspect the efficacy of the seed treatment has been compromised.
In corn, there are not a lot of options for insect control once the crop is up. If an in furrow insecticide, such as Capture LFR or a granular insecticide, was used in addition to a seed treatment, there is probably little reason to be concerned.
In rice, we do still have some options. The primarily target of insecticide seed treatments is rice water weevil. If the seed treatment was compromised, you will be able to determine that based on leaf feeding from the adults and an insecticide can be applied if leaf feeding is extensive. There are a couple of options available for foliar control now. Pyrethroids and Dimilin have been available for several years and provide good control when they are timed right. Another option is Belay. Belay received a registration last fall and is now available for rice water weevil control in rice. Our research has shown that Belay is less sensitive to application timing than the other options, probably because it moves into the plant and has systemic activity. It is important to note that Belay can not be used in rice that had Nipsit INSIDE as a seed treatment.
The bottom line is that what has been planted up to this point has gotten off to a slow start. Continue to scout the crop and give it what it needs to get off to the best start possible.