Category Archives: Cotton

Spider Mites In Cotton

With this heat, it gets dry quick. I found a few plants with evidence of spider mites yesterday. This of course is not good since it is early. When we are scouting fields, look for spider mites. Look for the reddening on the “V” part of the leaf. UGA Extension Entomologist Dr. Phillip Roberts says early detection is critical.

**The best management practice is to NOT flare spidermites with unnecessary insect sprays. If our retention is good (plant bugs), stink bug threshold is low, and aphids have crashed, we need to hold back. It’s about to get hotter, and dry weather makes them worse too.

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Cotton Blooming: Insect Update

Some of our earliest planted cotton is now blooming. I thought it would be good to go through an insect update.

Aphids / Beneficial Insects

As reported last week, we found the aphid fungus in Thomas County. UGA Extension Entomologist Dr. Phillip Roberts located the fungus in Tift County last week. Once it’s found in a field, it takes about a week to ‘crash’ the aphids. There are still reports of aphids this week, and I’ve had a question or two. Remember, UGA has not found any yield difference in treating aphids. We’ve had more aphid populations this year, but I would hesitate on treating, especially when they are in ‘hot spots.’ We need to watch beneficials.

In one field this week, I saw many, many lady beetles. On one plant, I saw almost all of its life stages, confirming how many beneficials are in our fields now. The lady beetles can’t eat all these aphids, but the aphids are bringing them to the field. I’ve seen some parasitic wasps too.

Lady beetle puapae

Lady beetle larvae – “Baby alligator”

Plant Bugs

I haven’t talked about plant bugs this year. In fields I go in, retention has been good. 80% retention is our goal. I have seen a plant bug here and there. Dr. Roberts says that in the state, they have been spotty, and only a small acreage has been treated to date.

Sting Bugs

It is now time to scout for stink bugs in blooming fields. Scouts need to crack bolls and look for warts and calloused walls. Treatment decision is based on % of bolls damaged.

Silverleaf Whiteflies

Dr. Roberts says whiteflies are a month early. This is usually an indication of a rough year. We need to look for adults. The precense of adult whiteflies influence deicisions of other pests. Treatment for whiteflies must be timely as well. For more on thresholds and insecticides, visit this previous post on Silverleaf Whitefly Management.

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Managing Silverleaf Whiteflies In Cotton

Probably the biggest agriculture pest topic last year, whiteflies became a problem very fast. Because of our warm winter, white are already present, likely meaning another bad year. The goal in silverleaf whitefly (SLWF) management is to initiate control measures just prior to the period of most rapid pest population development. UGA Extension Entomologists Dr. Phillip Roberts and Dr. Mike Toews put together some info on SLWF:

Risk for SLWF

  • Hairy leaf > smooth leaf cotton.
  • Late planted > early planted cotton.
  • Hot and dry > rainy conditions.

Scouting

SLWF adults (solid white wings) and immatures will be found on the underside of leaves. SLWF populations are best estimated from the 5th main stem leaf below the terminal. Main stem leaves are attached directly to the main stem by their petioles. The top or first main stem leaf is defined as the uppermost leaf which is 1 inch or larger in diameter. Adults and nymphs should be counted on the 5th main stem leaf below the terminal.

Adult whitefly in our UGA On-farm Variety Trial on June 29th. Leaves are considered infested when 3 adults are observed. (This counts adults that fly off when leaf is turned over.

SLWF Threshold

Treat when 50 percent of sampled leaves (sample 5th expanded leaf below the terminal) are infested with multiple immatures (≥5 per leaf).

Leaves are considered infested if 5 immatures are observes.

Insecticides

Insect Growth Regulators (Knack and Courier): use of IGRs are the backbone of SLWF management programs in cotton. Effects on SLWF populations are generally slow due to the life stages targeted by IGRs, however these products have long residual activity and perform very well when applied on a timely basis.

Use of other insecticide options which are active on all life stages have quicker effects on SLWF infestations but lack the residual of IGRs.

SLWF is an areawide cross commodity problem. When all parties use sound SLWF management programs all will benefit.

Steps for Efficient Sampling of SLWF

  1. Familiarize yourself with the general location of the 5th main stem leaf in each field.
  2. Select plants at random at least 25 paces into the field and at least 10 paces apart, being careful to keep your shadow from passing over the plant you plan to sample.
  3. Turn the 5th leaf over slowly by its tip or petiole and count the leaf as infested with adults if it has 3 or more adults on it. Include in your counts any adults that fly up from the leaf as you turn it over.
  4. Detach the leaf by the petiole from the main stem. If it fails to snap off easily, you have likely sampled a leaf that is too high on the plant. Recheck your leaf position to make sure you are sampling the 5th leaf.
  5. Examine the bottom of the leaf for the presence of immature SLWFs. Count the leaf as infested if it has 5 or more immatures on the underside of the leaf. Sample at least 30 plants (leaves) per field.
  6. Calculate the percentage of leaves infested with adults and the percentage of leaves infested with immatures.
  7. Treatment is recommended when 50 percent of sampled leaves are infested with immature SLWFs.

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Weather & Disease Update

It’s hard to say we don’t want more rain, but more and more we’re saying just that. We’re having showers nearly every day or every other day, sometimes as much as an inch and a half. It’s starting to show up in the field where cotton is getting ‘wet feet.’ Some of our rain has come with strong winds. Our largest field of tobacco took a hit from these winds knocking plants to the ground in some places. The only hope is to stand it back up as best as possible. It is still causing issues with topping since the flowers on the ground began growing straight up.

We have a good crop of tobacco this year, but it was hit hard from strong winds and rain. Some areas completely blown to the ground.

Flowers turned from wind affects topping

From UGA weather station in Cairo, here are the rain numbers since the beginning of May.

Disease Update

Here is our latest disease update from UGA Extension Pathologist Dr. Bob Kemerait:

Southern Corn Rust: I was stunned when agents in our disease diagnosis class visiting a field in Morgan County found a very active spot of southern rust. Unbelievable because until yesterday, it had ONLY been found lightly in Seminole and Marion Counties. Obviously, as we expected, southern rust could be present anywhere in Georgia now.  Why it has not “exploded” yet is a mystery to me given the conditions we have had, but CLEARLY the spores have spread across the state.

The corn in that field as at hard-dough/early dent, so it does not need to be treated; however growers with later planted corn not yet at R6/dough stages should be aware there is at least some threat.

Target spot of Cotton: Perfect weather but I am NOT calling for an automatic fungicide application at first or at third bloom.  BUT I am saying that every cotton grower SHOULD be aware that these can be important and critical timings. As cotton approaches bloom, I hope growers can put some eyes and boots in the field and begin looking for it, lower leaves first. Weather is very favorable- growers with a history of disease in the field and those with high-input, strong yield potential should be the growers with the greatest chance for benefit. Target spot will not steal the entire crop, but it will take away a valuable portion of the crop.

Consider:  Growth stage (blooming yet?)  history of disease, reports from scouting, (have early symptoms been found?), what’s the weather like now and what is the forecast?  What is the value to the growing in a preemptive application “to be done with it”?

White mold and leaf spot in Peanut: We are seeing some of both.  Growers, don’t get behind!

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PGR Rainfast

We are 2nd and 3rd week into squaring now, and we’re starting to put out our plant growth regulators. I had an unexpected 1 inch rain at the house yesterday afternoon.With all the rain we are having, we need to keep in mind the ‘rainfast’ of our PGRs. Below has written out each of our mepiquat and mixed products. Generally, when a surfactant is used, we can cut the rainfast in half. Pentia is more expensive, but with a 2 hour rainfast (1 hr with surfactant), we may find it beneficial our current conditions.

 

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Aphid Fungus

For the first time, I am getting to see what ‘consistent aphids’ looks like in the field. Normally, aphid populations are sporadic, seen only in ‘hot spots.’ This season, they are prevalent in our oldest and youngest cotton. We looked at a field this week where every single plant was affected by aphids in the top 3 – 4 leaves (below). The only reason we don’t talk much about it is UGA research on treating aphids has never found a consistent yield response. The best thing is to limit stress on the plant, and our rainfall is helping us here.

Leaves of 8-leaf cotton curl due to stress of aphids

Classic symptoms of aphids in our cotton variety trial.

Aphid Fungus

But the real new is that yesterday, we confirmed the ‘aphid fungus’ in Thomas County. UGA Extension Entomologist Dr. Phillip Roberts already reported the ‘aphid fungus’ being spotted in Tifton this week. This means, aphids will soon crash.

We observed the aphid fungus, (Neozygites fresenii), which causes aphid populations to crash on the Tifton Campus on June 26, 2017.  We have also received some early observations from both north and south of Tifton.  The presence of grey, fuzzy aphid cadavers is indicative of the naturally occuring fungus (below).  Once observed in the field we would expect aphids to crash within a week.  We typically first observe the fungus in fields with high aphid infestations; and more specifically areas of those fields which were initially infested.  All scouts should be on the lookout for the fungus and be sure to report to growers.

Aphid fungus – Photo by Dr. Phillip Roberts

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Cotton Irrigation At Squaring

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.

ImpactofPre-BloomIrrigation-J.Whitaker-2012

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.

UGACheckbookMethod

Aphids???

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

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