Current Situation: The cotton crop ranges from just planted to second week of squaring. Cotton growers are applying herbicides and fertilizer to crop. Peanut growers are applying cracking sprays to try to clean up weeds. The corn crop ranges from VT (Tassel) to R2 (Blister) stage of development. Southern rust was found last week in Brooks County and Miller County today (June 13, 2022). Hay producers need to be on the lookout for Bermudagrass stem maggots as they have been noticed in area bermudagrass fields. The drought monitor still considers Colquitt County abnormally dry.
Cotton: Growers need to be monitoring their fields for plant bugs because populations have been spotty. Scouts and producers need to be aware of sweep net and drop cloth thresholds for plant bugs. The thresholds are below.
Sweep Net and Drop Cloth Thresholds:
Third week of squaring through bloom: Drop Cloth: 3 plant bugs/6 row feet, Sweep Net: 15 plant bugs/100 sweeps
First 2 weeks of squaring: Drop Cloth: 1 plant bug/6 row feet, Sweep Net: 8 plant bugs/100 sweeps.
Insecticides recommended for plant bugs include Orthene, Bidrin, Admire Pro, Diamond, Vydate, Transform, and Centric. Dr. Phillip Roberts, UGA Entologist, gives us a few comments on each:
Orthene and Bidrin are organophosphates. Orthene is very active on plant bugs, however it is also is hard on beneficial insects and tends to flare spider mites. Orthene does not have activity on aphids and would likely exacerbate aphid populations if present. Bidrin is also very active on plant bugs and hard on beneficial insects. The Bidrin label only allows higher use rates such as 4-8 ounces per acre from first bloom to 30 days prior to harvest. Bidrin will provide some control of aphids. Delaying use of Orthene and Bidrin until later in the season (after bloom) is advisable.
Transform is very active on plant bugs and provides good control of aphids and is not as hard on beneficials as the OPs. Centric provides good control of plant bugs and decent but sometimes erratic control of aphids. Both of these products would be good choices when targeting plant bugs on squaring cotton. Admire Pro (imidacloprid) has some activity on plant bugs and some activity on aphids and would not be the treatment of choice if plant bug populations were high. Vydate provides fair control of plant bugs and has little to no activity on aphids.
Diamond is an insect growth regulator and is only active on immature plant bugs. Diamond will not control adults. Diamond is used on many acres in the Mid-South where plant bugs are an annual problem. Diamond performs best when applied before the situation is out of control. If you have fields where high adult populations have been observed and nymphs are starting to be found, Diamond would be a good option. In situations where adults are also being found, a knock down insecticide for adults will also be needed.
Aphids: Aphid pressure has been low in Colquitt County cotton. I ran across a couple fields last week with low populations.
How much do we need to irrigate early season cotton: According to Wes Porter, UGA Irrigation Specialist, Based on planting observations and where most of the crop is, most farmers should fall within the first square to first flower stage (or the yellow highlighted area) throughout the month of June.
If you were unfortunate and did not get your cotton planted until later May or early June then you will fall into the emergence to first square stage (highlighted in red). Crop water requirements increase dramatically from squaring and flowering. From 30 days to 50 days after planting, water consumption almost doubles. Keep this in mind as we move into middle and late June, and into early-July. Don’t fall behind on your irrigation once the crop reaches squaring and into flowering. As a reminder don’t forget that typically as water use increases is in late-June through July, usually so does very hot and dry weather, so keep this in mind and stay on top of your irrigation applications. Conversely, don’t over-irrigate the crop as there are yield penalties for doing so. Please keep in mind, if you have been using soil moisture sensors and you have “weighted” your sensors as discussed in the last newsletter, do not forget to change the weighting to reflect current crop water use in the profile. Root growth has dramatically increased downward and we now need to be more balanced with our sensor readings.
One last consideration, top dressing all cotton and our first dose of growth regulator on aggressive irrigated growing cotton will soon or has already taken placed. Don’t go into this stage with the mindset of “I’m going to hold back on the water now because I don’t want it to take off”. If proper growth regulator is applied, it will prevent vegetative growth as it should. If rain chances are low, irrigation will be required to get the fertilizer in the plant by irrigating it in and allowing the plant to uptake the nutrients.
What are some programs for controlling goosegrass? According to Stanley Culpepper, UGA Cotton Weed Specialist, all fields must begin free of this pest at planting and should include a residual at-plant herbicide such as Warrant or Prowl. Roundup is an effective option but only if the weed is small, the full glyphosate rate is applied, and conditions are favorable. The addition of residual herbicides such as Dual Mangum, Outlook, or Warrant should be included with Roundup. Liberty is marginally effective on goosegrass at best. Mixing Roundup and Liberty will reduce the activity of Roundup on goosegrass; thus, for goosegrass apply Roundup without Liberty if possible. POST grass herbicides can also be effective but must be applied very timely; these products can be mixed with Roundup but mixtures with Liberty are quite antagonistic. Goosegrass resistant to Roundup and POST grass herbicides are present in nearby states.
Peanuts: I have been getting a question or two about yellow nutsedge control in peanuts. According to Dr. Eric Prostko, don’t expect to see much much from Cadre on yellow nutsedge for at least 21 days after application. Cadre must be absorbed by both the leaves and roots for it to be the most effective. POST applications of Cadre in dryland peanut fields that have not gotten much rain after application will likely provide less than optimum control.
Tank-mixes of Basagran/Broadloom (bentazon) with Cadre will NOT improve the control of yellow nutsedge. In fact, it could cause antagonism.
What about lesser cornstalk borers? I have had numerous questions about lesser corn stalk borer in peanut. According to Dr. Mark Abney, UGA Peanut Entomologist, hot, dry weather is the most important factor contributing to LCB outbreaks. There are several dozen LCB pheromone traps in south Georgia peanut fields, and many of them have been catching moths. We should be aware that moths are currently active, and we need to scout fields that are at high risk (dry, sandy soils and skippy stands). There is no need to make preventative treatments for LCB; scouting and treating when larvae are at threshold will save growers money.
Below is a video about scouting for LCB in peanut (it is re-posted below). The video highlights the importance of random sampling to achieve an accurate assessment of infestations. LCB moths prefer to lay eggs on or near plants in a skip. This is useful to know because it can help you quickly determine if the pest is present in a field, but it is important that you do not check only plants in skips. This will result in a biased count that overestimates population size.
Lesser cornstalk borer is a dry weather pest, but it can and does infest irrigated fields especially prior to canopy closure. We cannot keep bare soil wet enough to eliminate the pest with irrigation. Once the row middles are covered, we generally see LCB problems dissipate if rainfall and/or irrigation are adequate. While they do not survive well in moist conditions, one or two rainfall events will not eliminate infestations.
Treatment options for lesser cornstalk borer in peanut include chlorantraniliprole (Vantacor) or novaluron (Diamond) applied as broadcast foliar sprays. Treatment threshold for lesser cornstalk borer is 30 percent of the spots there are checked in the field contain this pest.
Here are some thoughts from Dr. Bob Kemerait as far as spraying for southern corn rust:
• Single mode-of-action products are “good” but have a two-week protective window.
• Mixed mode-of-action products have a three-week protective window and better efficacy than do single
mode of action products. Products like these work well, especially when risk is heightened but fields are
sprayed before rust is established in a field.
Will we need to spray twice- now and 3 weeks later?
Possibly. But if you get the fungicide out in a timely manner, a second application may not be needed and, if it is, you may be able to use a less expensive product,
What should our growers spray?
I prefer they use a fungicide that is a mixed mode of action product combining different fungicides. Yes, I have had very good success with Trivapro, Headline Amp, and Veltyma. But I have also seen strong results from other products like Aproach Prima, Stratego YLD, Delano, Fortix, Lucento, etc.
Bob, do you expect the spread of southern rust to continue?
Absolutely I do. Southern rust loves hot. It is dry, but irrigated corn will certainly be a good habitat for
southern rust. UV radiation from clear blue skies could thwart survival of spores in long-range spread, but
certainly spread will continue in Georgia and the southeast.
Bob, you sure like to spend my money. Your fungicide applications are cutting into my profits that are already crippled by diesel prices. How sure are you that spraying my corn at tassel is going to make me money?
Obviously I can’t be 100% sure and ultimately to spray or not to spray is your decision. But I can tell you 3
things. 1) we have now found southern rust earlier than I have ever found it. 2) I believe conditions are quite favorable now for spread. 3) the key to controlling rust is to protect against it before it is present, or at least well-established in a field. Never has a grower who has lots of southern rust in his field late in the season but who didn’t spray tell me he will do that again.
So Bob, you tell us who “should spray”. Is there anyone who can wait to spray?
I would not spray non-irrigated corn if yield potential is low. I would not spray corn in South Georgia that is not at least starting to tassel. I would not spray corn in the Piedmont or northern Georgia. I would hesitate to spray corn where you have a good scout in the field who has not found rust.
Bermudagrass stem maggot….
I have started seeing bermudagrass stem maggot damage in a few bermudagrass hay fields over the last week. Growers need to be out looking for damage in their hay fields if it ever rains again.