Category Archives: Entomology

Forage Insect Update

We have had an interesting year so far in our hay crop. Our dry Spring kept us from truly getting started, and the current rain is keeping growers from cutting. We have hundreds of acres that hasn’t been cut yet. If it has been cut, it’s mostly been cut once. There is a very small amount of hay that has been cut twice.

This may be one reason we are seeing stem maggot in some fields. I stopped by this field Wednesday, and a large section appeared frosted. Stem maggot has done lots of damage here. The good news is we have yet to see fall armyworms. This too may be cause the rain.

UGA Extension Forage Specialist Dr. Dennis Hancock has given an update on some other insect issues throughout the state:

Bermudagrass Stem Maggot

Damage from bermudagrass stem maggot

Reports of the bermudagrass stem maggot have been coming in from all over the Coastal Plain and into the southern 2-3 counties in the Piedmont. I suspect with the abundant rainfall in most places, we will see BSM pressures similar to the heavy pressure we saw in 2013. Producers need to employ the standard suppression technique (labeled pyrethroid of their choice 7-10 days after cutting and again 7-10 days later, as needed). Moderate N fertilization rates, and good K fertilization minimizes disease and this seems to minimize BSM activity (but it doesn’t eliminate it). In the past, we have recommended spinosad, as well. Current research indicates this is not as effective as we believed it to be. Pyrethroids are our best option currently. We have a new Extension bulletin on BSM found at Bermudagrass Stem Maggot Research Update.

Fall Armyworms

Reports of fall armyworm are also starting to come in. Producers need to scout and spray if the threshold is reached. The newest bulletin is Caterpillar Pests in Pastures and Hayfields.

Where BSM activity is high and FAW pressure is imminent, consider using Besiege (Lambda-cyhalothrin for the BSM and active FAW; Chlorantraniliprole for residual control of FAW).

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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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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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Cotton Coming Up, Variety Trial Planted, Scout Thrips

Cotton is anywhere from just planted to cotyledon to 4 leaf at this time. Recent rains have growers planting and we hope to have more this weekend. It’s past our thrips date of May 10th and we have reason to believe thrips may crash soon this year – since we had a warm winter, they were active sooner. But remember, thrips live in the winter weeds along roadsides and move to our cotton and peanuts following germination.

From 0 to level 5, I’m seeing damage from none to about level 3, sporadic in most fields. Neonic seed treatments (imidacloprid, thiametoxam) are active on thrips for up to 14 – 21 days after planting. If we have no seed treatment, we need to be in the field checking the first true leaf. This is the best time when we need to apply a foliar application. Once we have 4 true leaves and the plant is growing fast, thrips foliar sprays are not economical.

Thrips injury on 1st true leaf

Threshold

Research has shown that foliar applications are still needed when thrips infestations are high. The best way to make this decision is based on current threshold of: 2 – 3 thrips per plant AND/OR presence of immatures. The immature (wingless) thrips will be yellow/green in color; the adult (winged) thrips are black. Take a white piece of paper and slap a plant on it. Give it a second for the thrips to start crawling. In this field, I have immature thrips present. This suggests are at-plant insecticides are no longer active, and reproduction is taking place.

Here is a note from UGA Extension Entomologist Dr. Phillip Roberts from 2016. It may still answer some question today:

Should we follow with a second acephate spray? Dr. Roberts has conducted trials with 1 +3 leaf sprays, and they showed no difference from a 1 leaf ONLY spray. Something I noticed rating our thrips trials (2016) is not only the effectiveness of 1 leaf sprays, but also how fast the plants grow in 14 days. If we have a timely insecticide spray, AND growing conditions are good, cotton will outgrow potential thrips issues. The only reason to consider a second foliar application is if 1) cotton is not growing fast 2) thrips are still highly active. It would be a judgment call at best.

How long does this foliar spray of orthene last? Research entomologist Dr. Michael Toews, and Dr. Roberts have data on this that hasn’t been totally put together, but the best analysis is maybe 3 -4 days. Pyrethroids, on the other hand, photodegrade fast. Dr. Roberts says pyrethroids will kill thrips, but the reason we do not recommend them is 7 days after treatment, thrips populations are higher where pyrethroids were sprayed than where orthene was sprayed.

We were able to plant our variety trial last Friday. I visited the field today, and cotton is just now coming up. The field is at the end of Centennial Road where it touches Airline Road. It is the one on the right. We ended up participating in the UGA On Farm Variety Trial. Most of the varieties I asked for were in the trial. We were able to get in all varieties I wanted plus these for a total of 15. We replicated three times in the field; reps are actually stacked on top of each other.

2017 UGA On-Farm Variety Trial

We got done real fast, thanks to Brandon’s precision planting. Thanks to growers Mike, Brandon and Chandler Barnes for planting the trial this year and Jodie Stringer (Boston Gin) for helping and Jessica Jones, owner of Barbaritoes, for feeding us in the field.

Jodie and Brandon fixing flags

Brandon Barnes, Mike Barnes, Chandler Barnes, Jodie Stringer, Andrew Sawyer

 Jodie and Brandon fixing flags

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