Some of our pivots have not been running these past few weeks thanks to steady rainy days. For being so dry at planting, this is hopefully going to get us off to a good start in the field. Below is a photo of rep 2 from our variety trial. We have some plants squaring already.
Remember, stressing cotton during squaring has more negative effects than we realize. Cotton does not rebound if stressed from no irrigation through squaring. Last year, we lost so many squares from drought stress. This is something UGA Extension Irrigation Specialist Dr. Wes Porter says we have to be careful about.
Data on this using the UGA Checkbook Method where pre-bloom irrigation was eliminated found no difference in non-irrigated cotton. The reason for this is that cotton grows vegetatively and reproductively at the same time. During its vegetative growth, cotton is setting nodes. If it is stressed during this time, less nodes are set.
Dr. Porter has been looking at soil moisture sensors and the irrigation apps we can download on our phone. Research does show that the Smart Irrigation App is keeping us from putting out more water than is needed during both drought and rainfall situations. This is interesting because these apps do not monitor soil moisture, and the Smart Irrigation App is no charge to download. We go one step further when we use soil moisture sensors.
I saw some ants crawling up some plants. I then checked for aphids. The ants eat the ‘honeydew’ produced by the aphids, called ‘farming aphids.’ UGA Extension Entomologist Dr. Phillip Roberts says there are some aphid hot spots that may develop in fields now. We just need to watch.
Aphids under leaf of squaring cotton
With rain and humidity, we are having ideal conditions for scab. Some growers essentially continue to spray around the clock. A common question is, “How long does my fungicide need to dry before rain?” This is a question pathologists have worked on for some time, but there are many variables involved making it difficult to generate data. UGA Plant Pathologist Dr. Tim Brenneman recently offered the following suggestions based on his studies with pecan and also on similar studies he has conducted in peanut:
Highly systemic materials like phosphite must be absorbed into the plant. It may require as much as 1/2 a day for this process to take place so that the material can be highly effective. While DMIs and strobilurins or combination products like Absolute, Top Gard, Quadris Top, and Quilt have some systemic activity they are not as systemic as the phosphites. Still, they would need a little time to be effective, so several hours to half a day would be ideal. A surfactant (80/20 or other) would increase the uptake speed of these materials and would likely provide some benefit in the conditions we’ve had over the last week or so. However, do not include a surfactant with Phosphite.
While the DMIs and Strobis have some systemic activity they still function largely as protectants. Other materials like Dodine (ELast) or Tin are pure protectants. These materials (Dodine and Tin) would be the most prone to wash off when rain arrives shortly after spraying. Dodine does adhere tightly to the plant cuticle, which likely helps it. Rainfall that occurs less than one hour after spraying makes the fungicide pretty well ineffective. Any rainfall within 24 hrs after spraying with a pure protectant will likely reduce the effectiveness of control to some extent. For each additional hour between the spraying and rainfall you gain additional control.
Ideally, all fungicides should be applied prior to rain events. If circumstances prevent you from getting a spray on in time and you have to spray after a rain event, the DMI/Strobi combinations would be the best choice.
Filed under Disease, Pecans
Southern corn rust has been identified in Georgia (on June 5th) by Rome Ethredge in Seminole County. Corn was in the silking (R2) state. This is likely some of the earliest southern rust to affect our state. UGA Extension Pathologist Dr. Bob Kemerait has this update for growers:
- Weather condition for the past few days and over the next few days is predicted to have a significant chance of rain and humid conditions. These conditions are quite favorable for the development and spread of rust diseases to include southern corn rust and Asian soybean rust.
- As of today, 5 June- Asian soybean rust has been found on kudzu in Miller County and on corn in Seminole County.
- My recommendations: Corn in southern Georgia that is approaching tassel stage (or has reached) is now at some risk to southern corn rust. The risk is likely not urgent yet, but finding rust now (fairly early in the season) and coupled with the current weather conditions does increase risk.
- Grower spraying for southern corn rust: tebuconazole is effective, but combination products that include multiple modes of action (e.g. strobilurins, triazoles, SDHIs) have a broader spectrum of activity against disease AND have a longer protective window (e.g., 3 weeks versus 2 weeks.)
The picture above is corn in Thomas County that is also silking. We are very fortunate with our rain these past few weeks. During this stage (70-80 DAP) corn is still using 0.3 inches of water / day. We also need to watch for stink bugs. It is common to treat during the ear elongation / tassel state (VT) is 1 SB per 2 plants is present. Because they can hide from you, it is easiest to drive down the rows and check.
During policantion and blister statges (R1-R2), SB feed through the husk and damage individual kernels. Treat if you see 1 per plant.
Pyrethroids are fine to use when we’re seeing southern green SB. If brown SB are prevalent, use a high rate of bifenthrin to get about 75-90% control.
1st Instar Brown Stink Bug
We plant a lot of peanuts on plantations here in Thomas County. As we were finishing up peanut planting, manager at Wild Ridge Plantation Jason Sanders made a great video of them planting near the Florida line. They filmed it with a drone camera. Jason did a great job making this video. I think I need to get my ‘video band’ down to Wild Ridge and get a band shot from this drone camera.
Our peanut crop is looking good since we’ve had a few weekly rains. Fungicide programs are starting up now, and we’re still needing some rain. We had a few showers this week, but not much to count. UGA Extension Weed Scientist Dr. Erick Prostko has this update on valor that I want to share:
Peanuts that were planted approximately the last two weeks in May were in a great place to get hammered from Valor because of the Sporadic heavy rainfall events (below). If you received one of these heavy rainfall events on Valor treated peanuts when they are cracking and small (~2 weeks after cracking), injury will occur.
Georgia Rainfall Totals from May 20 – May 24, 2017
Peanuts typically recover from this injury without a yield penalty. In a 2009 research trial, more than 5″ of rainfall occurred in the 30 day period after peanut planting. Peanut injury was significant but yields were not reduced even at a 2X rate.
Valor injury to peanut. Photo by Dr. Erick Prostko
Here is an update from UGA Extension Pecan Specialist Dr. Lenny Wells:
Pollinated pecans begin to form
We have had a heavy bloom of female flowers and a good early nut set on ‘Desirable’ this year, but anyone that has been around pecans for long knows this cultivar has a nut drop in June each year. When this occurs the trees may drop as much as 30-60% of the nuts on the tree. The June drop continues to about 40-45 days after pollination, and is due to the lack of successful fertilization of the egg and sperm. This is an inherent characteristic of ‘Desirable’ in particular and this self-thinning is also the reason this cultivar can have consistent production from one year to the next
‘Stuart’ will also have a June drop but it is usually not as severe or as noticeable as the ‘Desirable’ drop. There is nothing you can do about this drop and there is nothing wrong with the trees when it occurs. If seeing this drop bothers you I recommend not going into the orchard to look until its over. Desirables always drop down from 4 and 5 nuts per cluster to 0, 1 and 2 nuts per cluster. The trees will still have good production. I began seeing this last week and it will likely continue for a week or so.
Some of our dryland corn is now tasseling. The rest of our corn is very, very close to tasseling, and many growers will put out a fungicide. And this is okay. Should we have sprayed before now? UGA Extension Pathologist Dr. Bob Kemerait has found that early fungicide applications (V5-V6) on early planted (Spring) corn has no benefit to yield and disease, but can have “some” benefit on later planted corn. This is likely because corn planted behind corn will be affected earlier in the growth stage.
Former Seminole County Agent, Rome Ethredge found northern corn leaf blight (NCLB) last week. In corn disease, we are mostly watching for southern corn rust and NCLB. We have sentinel plots in the county to help us watch for rust. Unlike NCLB, southern rust is reintroduced each year and spores essentially blow in and re-infect corn.
Lesions o NCLB appear as a cigar shape. Photo by Rome Ethredge.
Control of NCLB
Northern corn leaf blight is more prominent where we have corn behind corn, overwintering in the leaf litter as well as irrigated corn. We have less of both situations in Thomas County. In fields with a) susceptible varieties and b) favorable conditions, you can have some NCLB in the field and NOT need to spray. When do we pull the trigger on spraying NCLB?Dr. Kemerait says treat for NCLB when lesions get as high as 3rd leaf from the ear leaf.
Filed under Corn, Disease