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.
We were looking at sorghum where damage form WSCA has been evident. But also seeing heads and stalks that are brown. The brown color on the outside and inside of the stalk turned out to be Charcoal Rot (Macrophomina phaseolina). Grain sorghum plants affected by this fungus won’t fill grain properly and may lodge in the latter part of the season. Infected stalks show an internal shredding at and above the ground line. When you split the stalk, you can see the small black dots from microsclerotia (below):
Below is information regarding control from UGA Extension Grain Pathologist Dr. Alfredo Martinez:
“Charcoal rot is particularly damaging under hot, dry weather specially post-flowering periods. Therefore maintaining soil moisture during these periods can help minimize the incidence of the disease. A balanced fertility program is beneficial, high N and low K should be avoided. Excessive plant populations should be also avoided. Growing drought tolerant sorghum can reduce losses.”
Microsclerotia under dissecting microscope
The 2013 growing conditions continuing through early 2014 has increased the cost of production resulting from a rise in the number of fungicide sprays required on scab susceptible cultivars. The number of sprays has also risen as spray intervals shorten. And finally, growers are using higher fungicide rates because of insensitivity issues. All of this adds to the cost of production in which UGA Extension Pecan Specialist Dr. Lenny Wells and New Mexico State Pecan Specialist Dr. Richard Heerema have put together information on this topic. Below are notes from Dr. Wells:
“It looks as though this led to a 60% increase in the cost of scab control alone as you go up from 10 sprays to 16 sprays. In addition to the increased cost of managing pecan scab, black aphid and mite pressure were high in 2014. Both of these pests are expensive to control and many growers had to spray multiple times for both pests, which also increased the cost of pecan production. See the graph below for a breakdown of the annual variable cost of production, which totals over $1600/acre with 16 fungicide sprays.
At such a high cost growers are justifiably concerned about the price they need for their crop. See the chart below for break-even prices for pecans at various prices and yield levels given a cost of $1628.15/acre:
In a ‘normal’ year—neither too wet or too dry—10 fungicide sprays will usually be enough to manage scab. This brings the cost down to nearly $1500/acre as you can see below. Break even prices at a cost of $1485.88/acre follow:
Keep in mind that these are all variable costs only. Fixed costs like land payments, equipment, overhead, etc. will increase the total cost of production by another $450 or so. The cost of production will vary from one grower to the next but these numbers should give some idea of what the general cost may be for growing pecans.”
Filed under Disease, Pecans
An Area Wheat Meeting with Colquitt, Mitchell, and Thomas Counties will be held next Wednesday, Oct 1st. The meeting will be at the Colquitt Co. Ag Center (350 Building 1 Veteran’s Park North Moultrie, GA 31788.) UGA Extension Agronomist Dr. Dewey Lee will be keynote speaker. We’ll discuss cultural practices, varieties, weed, and pest management. Please call the Thomas County Extension Office at 229-225-4130 to RSVP by September 29th.
A grower called me to look at a pond in the middle of a cotton field where fish had been dead a few days. There are a mixture of bass and bream that have died. I asked which fish died first, and he said the larger fish. Fish kills can often be associated with chemical runoff or oxygen depletion. When larger fish die first, it is generally the result of some kind of oxygen depletion, since lack of oxygen would affect larger fish first. UGA Extension Aquaculture Specialist Dr. Gary Burtle said there have been several fish kills related to low oxygen in south Georgia in the past week. With rain comes cloudy weather and low oxygen has been a problem recently. Below is what Dr. Burtle has to say:
“The usual reason for fish death after rains is a partial oxygen depletion caused by the influx of water which has no algae in it or a high concentration of bacteria in it. When algae are replaced by bacteria, the water turns brown in color and oxygen concentration drops. Bass are larger than bream, so may be affected first. The oxygen stress may cause the fish to become susceptible to disease, so fish deaths may occur for several days after the partial oxygen depletion.
When the pond begins to ‘green up’ again, oxygen concentrations will increase and fish deaths stop. Until oxygen concentration returns to normal levels, low oxygen each morning or during cloudy weather may cause more fish stress and death. The solution is to install an aerator and operate during cloudy weather, which seems to be more prevalent in Georgia in the late summer and fall.”
We were able to look into some defoliation Friday. Varieties play more of a role with PGR management whereas environmental conditions play more of a role with defoliation. With the standard 3-way approach (Ethephon, thidiazuron, and tribufos), we do not want to cut our rates is with thidiazuron since regrowth potential is high during this time. There has also been reports of leaves sticking after spray. This is making us drop our desiccant rates in hot temperatures. Not only can too much of an increase in of any product cause leaves to stick, crop oil in the mix can play a roll also. Many are using lower as desiccant rates with hot temperatures. We are in an 8 – 12 oz/acre range of Folex at this time.
Another issue we we’re discussing is weeds. Some growers are still fighting some grass. In this case, it is okay to add a quart of RoundUp. If there is morningglory, we can at an ounce of Aim or 0.5 – 2 oz of ET. If we decide to add a herbicide UGA Extension Cotton Agronomist Dr. Guy Collins advises we follow by cutting back our desiccant rate. (If using 10z of Folex, cut back to 8oz, for instance.)
With so much attention on peanuts this week, cotton is starting to be defoliated in the county. We were looking at some fields this morning to make decisions on defoliating. There are a few different methods from the 2014 UGA Cotton Production Handbook we could check to make decisions.
- Counting bolls – We can defoliate when 60%-75% of bolls are open. This method focuses mainly on the “open” portion of the bolls, but ignores the “unopen” portion.
- Slicing bolls – Slice the boll in half with a knife. Bolls are mature and ready for harvest aid applications when they cannot be sliced with “stringing” the lint. Also, bolls are mature when the seed embro contains only tiny folded leaves (no ‘jelly’ within developing seed) and the seedcoat begins to turn yellow or tan.
- Nodes Above Cracked Boll (NACB) – This is determined by counting the number of nodes between the uppermost first position cracked boll and the uppermost 1st position boll that is expected to be harvested. Once NACB reaches 4, we are generally safe to defoliate.