We have a lot of attention on white mold in peanuts now. This has definitely been a white mold year. I’ve noticed tomato spotted wilt also. Here is a field last week abnormally high TSWV, especially considering their planting date and at plant insecticides. Below are comments from UGA Extension Pathologist Dr. Bob Kemerait:
- WHITE MOLD ON PEANUTS has been EXTREME this year for many growers because of prolonged, very warm temperatures and, at times, adequate rainfall. NO PROGRAM will stop all white mold, BUT your program should be able to CONTAIN “hits” of white mold to a few plants and not to long streaks in the field.
Angular Leaf Spot
Angular leaf spot and bacterial blight of cotton have been unusually common this year, though largely confined to SW Georgia. I am now receiving reports of some findings east of I-75.
- Target spot of cotton is now developing, quickly in some areas. Cotton beyond the 6th week of bloom is likely safe. NOTE: If you know of fields with target spot, please let me know as I need to collect isolates.
- Still no Asian soybean rust found in Georgia, though I expect it at any time. Any of our soybean crop that has not reached R6/full seed growth stage is still vulnerable if the diseases arrives.
- Further notes on white mold: A) Growers should consider prolonging their white mold programs, perhaps adding mixes of tebuconazole and chlorothalonil at the end. B) The labeled rate of tebuconazole is 7.2 fl oz/A (not a pint) C) GOOD NEWS! Cooler morning temperatures forecast this week (mid 60s in Tifton) coupled with a drier air mass should help to SLOW the development of white mold. D) Dryland fields may have less-than-desired white mold control IF rains have not been timely to more fungicides to the crown of the plant. This is NOT the fault of the fungicide.
Tomato Spotted Wilt
Tomato Spotted Wilt: “Honey, I’m baaaaaaaaaak…….” .. For the third year in a row, we are seeing an increase in Spotted wilt disease. We will discuss this more at (grower meetings). Dr. Culbreath and I visited a field last week in Evans County where the incidence of TSWV was ~65%.
Soybeans are reaching reproductive growth stage. It is now time to be scouting for caterpillars. We are looking for velvetbean caterpillars, green cloverworms, and soybean loopers.
- The velvetbean caterpillar has 4 pair of abdominal prolegs. This one will wiggle when touched and usually fall to the ground.
- The green cloverworm has 3 pair of abdominal prolegs.
- The soybean looper has 2 pair of abdominal prolegs. We need to check fields since not all insecticides target the same worm.
This field has been sprayed with Dimlin, which has been a UGA recommendation to spray as preventative at R2. However, I was still seeing 1 inch soybean loopers. This is because Loopers are not controlled by Dimlin as the other two caterpillars. This field is still under threshold nonetheless. We can also look at leaf damamge. Following flowering, leaf damage exceeding 15% needs to be treated. Below is a guide for scouting soybean caterpillars from UGA Extension Entomologst Dr. Phillip Roberts:
Many fields planted throughout plantation land see lots of wildlife damage, mostly from hogs. Effingham County Agent Sam Ingram put together some information on Controlling Deer through his blog. Here is a field of soybeans last year on a plantation where deer have damaged. This kind of damage early on can certainly decrease yield potential.
Deer may prefer these areas because of greater comfort. If this is the case, a grower may plant excess plants in these areas to allow for grazing and to limit the deer from encroaching past these areas. This is more of a sacrifice area than control.
Control options or deterrents are available, but efficacy or effectiveness is not proven for any of them:
- Milorganite® is used by many producers by application around the perimeter of the fields as a deterrent. Producers believe this product has worked well in fields in the beginning, but if the deer become accustom to the product or a rain shower washes the product it loses its effectiveness.
- Hot sauces- similar idea as the Milorganite® with it being placed around the perimeter. Similar limitations to the effectiveness with weather issues and the deer becoming accustomed to the product.
- Electric fence- This deterrent or barrier is the most troublesome to put in place but for fields with heavy deer pressure it may be worth the expense. Some factors to consider is the access to power or solar power and the understanding that a producer may have to repair/re-stake the fence throughout the season.
For more information on the potential yield loss and control options, here are thoughts from UGA Soybean and Cotton Agronomist Dr. Jared Whitaker:
“Some producers have said hot sauces or milorganite give some control. Unfortunately, we do not have any research behind the effectiveness of these remedies. But, looking at the potential loss in yield, every situation is different. If the deer graze the plant past the cotyledon, we lose all yield potential for that plant.”
Weather conditions now are nearly opposite of last year’s conditions as we were waiting for dry weather to plant. We are now in need for rain. Last year, Easter was April 20th. Easter has now past and it is warm. With warmer soil temperatures, many are asking if we can go ahead and plant.
For cotton, we need to have 65 degree soil temperature for 3 days and future warming conditions projected. For peanuts, we want 68 degree soil temperature. We are seeing warmer soil temperatures now, but we need to be aware of other early planting risks.
We struggled with thrips last season. Thrips live on field edges and along roadsides in weeds during the winter. When plants emerge, they move to our fields. If we are planting before May 10th, we know we will have an increase risk of Tomato Spotted Wilt Virus in peanuts. Irrigated cotton should usually be planted after May 1, since the risk of having adequate moisture is eliminated, thrips pressure is less, and the possibility of boll rot from August rains is reduced. Boll opening and harvest-time rainfall risks are reduced and harvest can be completed from late September through November, normally lower rainfall.
We were looking at planting date curves from different crops. Below is a graph UGA Extension Agronomist Dr. Scott Tubbs showed at our peanut meeting. Our largest yield window is late April through mid-May.
We also have a graph from UGA Extension Cotton/Soybean Agronomst Dr. Jared Whitaker on soybean yield with planting dates. For cotton, long term research has shown little yield difference in planting dates between late April and May 20th. We can show a yield loss in soybeans, because soybeans are a determinate plant. The plant must have a full vegetative set before it can produce fruit. Cotton is indeterminate, meaning it produces vegetative and reproductive growth at the same time. Remember to follow the Georgia Weather website for planting information.
Here are some soybeans down below Metcalf that were not able to be harvested since a creek washed out the road leading to these back fields. We wondered about aflatoxin issues but UGA Extension Pathologist Dr. Bob Kemerait says this is generally not an issue with soybeans. Because of the wet and dry conditions soybeans went through, the issue is going to be quality. UGA Extension Soybean Agronomist Dr. Jared Whitaker says this shriveling is a sign the beans have went through periods of wet and dry conditions. There is some mold is on the grain but not an issue. These beans are to be sold, so it maybe best to take some to the buyer and let them make an assessment. The quality is not as bad as we thought and would probably be some deduction when bought.
Here is a picture of early planted soybeans last Monday. Leaves are turning yellow and brown and falling off. The beans in the pods are at full maturity. Below is a photo of the same field taken yesterday.
Seminole Ag Agent Rome Ethredge posted about irrigation termination on Seminole Crop E-News saying, You are generally safe to terminate irrigation if you have good soil moisture when the seeds fill the pods and the pods start to change to the yellow color in the top 4 nodes of the plant. Mississippi State also has a good blog post concerning Soybean Irrigation Termination that goes into growth stage specifics.
UGA Extension Weed Scientist Dr. Eric Prostko warns us to avoid early-harvest-aid applications in soybeans.
“Early applications (>40% seed moisture) will likely result in significant soybean yield loss as a result of reduced seed weights (Below). The 40% seed moisture contest roughly coincides with the R6.5 to R7 stages of growth. R6.5 = Full Seed = all normal pods on 4 uppermost nodes have pod cavities filled. R7 = Beginning Maturity = one normal pod on main stem of all plants has reached mature color (Below). Official UGA soybean harvest aid recommendations can be found on page 517 of the 2014 UGA Pest Management Handbook. ”
Brown Stink Bug Adult
Early planted soybeans are progressing and looking good. Some varieties are drying down and some have already been harvested. These soybeans are progressing at R6 (Full Seed)growth stage now. R6 is defined as the beans inside the pod are touching. We’ve had some questions about stink bugs this week. Stink bugs, corn earworms and fall armyworms are recognized as soybean pod feeders. I ran a sweep net through a few fields on a plantation yesterday and the highest number I found was 5 per 25 sweeps, which is below threshold. Above is a brown stink bug adult in the field. Below is a green stink bug nymph. This is probably one instar from being an adult. Southern Green Stink Bug nymphs usually have pink/reddish markings on them.
Green Stink Bug Nymph
Our decision to spray for stink bugs is determined by thresholds. You can use either a drop cloth and shake plants over the row to count insects by row foot or use a sweep net. When the soybeans are this far along, I like using a sweep net. Below are thresholds in the 2014 UGA Soybean Production Guide from UGA Extension Entomologist Dr. Phillip Roberts:
- Bloom to mid pod fill – 0.33 stink bugs per row foot or 3 per 25 sweeps.
- Mid pod fill to maturity – 1 stink bug per row foot or 6 per 25 sweeps.
*beans being grown for seed production, 1 stink bug per 6 row feet will justify control.
- Should be controlled at any time after bloom when an average of 2 per row foot (1/2 inch or longer) are found.
Since the beans are at R6, we still need to treat for pod feeders if thresholds justify. Once we hit R7 (Beginning Maturity), we no longer need to treat for insects. R7 is determined when at least one pod can be found on the plant which is mature or brown/tan in color. Pods and leaves start to “yellow” during this stage. This field is not there yet.
Don Vick and I looked a quite a few cotton, peanut and soybean fields yesterday. We observed the most insect pressure in soybeans. This field is around R5, beginning seed stage. Walking in the field, it was easily to note the leaf damage. At this growth stage, 15% leaf damage is our threshold. I always like to do a ground cloth sample. If you sit down in the row and shake soybeans, you can count insects per row foot. I also used a sweep net.
This field needed to be treated based on foliage feeding insect thresholds. The caterpillars we were finding were soybean loopers and velvetbean caterpillars. VBC has 4 pair of abdominal prolegs and wiggles when disturbed. We had to check recommendations since soybean looper is resistant to pyrethroids and Steward does not have good activity on VBC. Also, they mixed another fungicide with it for Asian Soybean Rust. Here is an example of threshold for foliage feeders in soybeans:
We’re looking at a lot of early-planted soybeans and trying to decide on continuing insect and disease sprays. We know Asian Soybean Rust is in Alabama and on the Florida boarder. It has not been located in Georgia yet. Most of the fields have already been sprayed for disease and questions about spraying is coming up. I was talking with Colquitt Ag Agent Jeremy Kichler this morning and here are some of the considerations about follow up disease sprays:
- How long ago and what did you last spray? Some fungicides last two weeks and others last three weeks.
- Growth stage – Many of our early-planted soybeans are in full pod (R4) or beginning seed (R5) growth stage. Once the plant reaches R6 – seeds are touching inside the pod – soybean diseases are not an issue.
- Environmental conditions – Right now we are very hot and moving to a hot weekend with high temperatures and almost no chance of rain until Sunday. On through next week, we have smaller chances of rain until the end of the week. If lots of rain show in 10-day forecast, conditions are more conducive for disease.
- Importance of 1st Spray – Most of our fields have been sprayed soon after bloom. UGA Extension Pathologist Dr. Bob Kemerait says, “From field studies, it is clear that the FIRST fungicide application is more important than the second. In 2006, a well-timed application of our best fungicides was at time as effective as two fungicide applications, and sometimes better than two application of a lesser effective fungicide.”
We’ve also been checking insects this week. I’ve not seen a lot of kudzu bugs at all. The most insect pressure is coming from foliage feeders – mainly loopers. UGA Extension Soybean Entomologist Dr. Phillip Roberts says it is usually going to take 8 or more per row foot to cause 25% leaf damage. Right now, insects are below thresholds. Growers can terminate insecticide applications when their soybeans have reached the R7 growth stage and are mostly insect pest free. This is when at least one pod can be found on the plant that is mature (turning brown or tan).