Monthly Archives: August 2014

August 29, 2014 · 2:16 PM

White Sugarcane Aphids

We were looking at sorghum yesterday and saw many, many aphids with a lot of honeydew on the lower leaves. Some sorghum is not producing heads just yet. The aphid turns out to be a new aphid in the state, white sugarcane aphid(Melanaphis sacchari). The initial problems found with these aphids in Texas were discovered during harvest, since the large amount of sticky honeydew produced by aphids choked combines and losing grain. UGA Extension Grain Etnomologist Dr. David Buntin says, “Subsequent reports find the aphid in 9 total counties in the southwest quadrant of the state Marion, Decatur, Early, Seminole, Colquitt, Taylor, Terrell, Randolph, and Tift counties.” (Now Thomas.)

Here are some more notes by Dr. Buntin:

“The white sugarcane aphid (WSCA) has occurred in Florida since 1977 and Louisiana since 1989 feeding on sugarcane. About 2 years ago the aphid shifted its host preference to grain and forage sorghums. First found in Texas, this new strain has rapidly spread eastward across the southern United States in 2014 and is now widespread in Mississippi, Louisiana, and eastern Texas, and Arkansas. It is expected that WSCA will continue to spread rapidly throughout Georgia over the next few months. It is important to scout sorghum fields in your area for its presence. It is fairly easy to identify. Wingless forms are a uniform pale cream to yellow with black feet and black cornicles (the small tubes present on the end of the back).

Where it has been found in Georgia, it is present in many fields at very high numbers of several thousand aphids per plant across entire fields. The aphid sucks plant fluid and these large populations are causing injury to the plants including death of leaves and sometimes plants. The aphid remains present in field until harvest. It produces large quantities of honeydew, a sticky sugary substance that adheres to the plants, which may interfere with harvest and may damage combine harvest equipment. Entomologist in Texas, Louisiana and Mississippi report 20 to 50 % yield loss and sometime the total loss of the crop from harvest damage. A tentative threshold is: treat if more than 30% of plants are infested AND there is an average of 100 – 250 aphids per sorghum leaf. This publication from Texas AgriLife Extension shows the different aphids on sorghum and information about white sugarcane aphid biology and damage: http://nueces.agrilife.org/files/2014/05/Sugarcane-Aphid-Publication.pdf Interestingly, a study by Kathy Flanders at Auburn University suggests this new strain prefers sweet, grain and forage sorghum over sugarcane and it does not attack millets.

WSCA is difficult to control and populations may bounce back quickly following an application. Currently labeled insecticides in grain sorghum are not adequate. High rates of Lorsban (24-32 oz) appear to provide decent control but cannot be used for late-season infestations because of the 60 day preharvest application restriction. Dimethoate, malathion and the 1-pint rate of chlorpyrifos provide only about 50% control. Pyrethroid insecticides are not effective and may flare aphids. If headworms occur, consider using Belt or Prevathon for control. The states of Texas, Louisiana, Mississippi, Arkansas and Oklahoma have a Section 18 (emergency use exception) exception approval to use Transform WG (sulfoxaflor, Dow AgroSciences). Studies in these states show an application of 1.0 – 1.5 oz per acre is about 90% effective, although aphids can build back in a few weeks. We are working on a section 18 emergency use exception request for Georgia, but Transform WG is currently not allowed in Georgia.”

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Filed under Entomology, Grain Sorghum

August 29, 2014 · 12:37 PM

Soybean Caterpillars

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:

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Filed under Entomology, Soybeans

August 27, 2014 · 8:30 PM

Boll-Feeding Insects

Cody Weaver and I were checking quite a few cotton fields this morning. At 8th week of bloom, and our stink bug threshold moves into the 50% range since there are so few bolls left stink bugs are likely to damage. The highest damage we found was 10%. We did see a leaffooted bug which is also a boll- feeding insect. It is in the same insect order, Hemiptera, as stink bug but in the family Coreidae. They also have piercing-sucking mouthparts. UGA Extension Entomologist Dr. Phillip Roberts says we cannot decipher the damage from a stink bug, leaf-footed bug, plant bug, etc. We just check for damaged bolls and include them in our percentage. Here is a damaged boll we found with both lint and warts.

We’re also seeing lots of dropped bolls resulting from drought conditions. There were not has many bolls opening in these fields. We also identified many minute pirate bugs, a beneficial insect. They are easier to see in the blooms since they are small and black colored.

Leaffooted Bug

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Filed under Cotton, Entomology

August 26, 2014 · 4:51 PM

Late Season Peanut Weeds

Some hemp sesbania, sicklepod and pigweed escapes are some weeds we are seeing in peanuts now. Questions coming in about tank mixing with fungicides and non-selective applications. Below is information from UGA Extension Weed Scientist Dr. Eric Prostko:

Can I tank-mix Mn fertilizers with herbicides and/or fungicides? Recent research from NC State University indicated that manganese did not affect the efficacy of Select, Poast, Cadre, Pursuit, 2,4-DB, Abound, Bravo, Headline, or Folicur. Common ragweed control with Cobra was reduced 6% by dry Mn sulfate but not liquid Mn. (Peanut Science 2012 39:1-8)
What weeds can be controlled using non-selective applicators (NSA) such as the Weed-Wiper or ropewick? UGA has data to suggest that Palmer amaranth, Florida beggarweed, and sicklepod can be controlled late-season with NSA using a 50% solution of paraquat. Refer to page 452 of the 2014 UGA Pest Control Handbook for additional information. Remember that the only benefits of this type of application would be improved harvest-efficiency and fungicide spray deposition. It is way too late to recover any competition related yield losses.
Is there anything that can be done to help control Benghal dayflower/tropical spiderwort at this time of the year (i.e. 100+ day old peanuts)? No. Revenge sprays are not practical. Dayflower/spiderwort plants at this time of the year are too big to control with herbicides. Additionally, late-season applications of herbicides such as Strongarm could have a significant impact on 2015 crop rotations. Although Aim can be used as an harvest-aid, previous research has shown that single applications to 8-10″ tall spiderwort plants provided < 45% control.

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Filed under Peanuts, Weed Science

August 26, 2014 · 4:49 PM

Possible Resistance Issues In Curcubit Downy Mildew

Pumpkins are really difficult to grow here because our disease and insect pressure is so strong at normal planting time. Here are some that have been flowering for a few weeks and first we saw flowers dropping. It turns out that these are male flowers with the long stems. It blooms for a day. The female flowers have shorter stems and come out usually a week after. With the heat this weekend, likely caused us to lose some flowers. For now, we need to watch for the female flowers and make sure those are not dropping. They have a 1-2 inch stem with a swollen base were pumpkin is forming.

We also have to be aggressive with disease prevention. Here is some early signs of downy mildew. There are some resistance concerns we need to be aware of with downy mildew in curcubits. Here is an update from Hunt Sanders, Disease Management Specialist in UGA Department of Plant Pathology:

“Based on what we are seeing in our cucumber trials this year, we may be experiencing some fungicide resistance problems in downy mildew of cucumber this fall. Some plots that have been sprayed with a Ranman/ Zampro rotation have a great deal more downy mildew in them than we are used to. We are using an older cucumber variety in these trials with no downy mildew resistance, but we still should not be seeing the level of disease severity in these plots that we are seeing. The trial in question is an industry trial with different fungicide rotations which makes it hard to determine which product (Ranman or Zampro) might be experiencing a problem. We have initiated a follow up fungicide screening trial that will help clear up what we are currently seeing. Results from the screening trial should be available in 3-4 weeks. Until that time all we know is that we are seeing increased levels of downy mildew in plots that were sprayed with a Ranman/Zampro rotation. I have been in contact with Dr. Langston about current downy mildew recommendations and

Downy Mildew – Pumpkin

we both want to stress how important it is to tank-mix products that contain mancozeb or chlorothalonil with the products Ranman or Zampro. In the current environment it is critical that your growers tank-mix these products. If you have a grower that experiences an outbreak of downy mildew that he cannot control with the current fungicide recommendations please contact me and I will investigate the situation.”

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Filed under Disease, Vegetables

August 21, 2014 · 8:36 PM

Terminating Pest Applications On 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).

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Filed under Disease, Entomology, Soybeans

August 20, 2014 · 3:01 PM

Water Stage Fruit Split

Pecans are looking good in the county. Growers are trying the keep the weeds down and the insects out mostly. We’ve had a little rain every few days these past two weeks. This is helping with herbicide being taken in by the weeds. Scab pressure is apparent still, but growers are keeping it off the nuts. Right now, scab is more evident on the leaves and stems. The main thing we are fighting is pressure from mites.

Water Stage Fruit Split

We are still seeing some nuts dropping, and this is mainly from water stage fruit split this time of year. UGA Extension Pecan Horticulturalist Dr. Lenny Wells says, “Water split is associated with rainfall occurring at the initiation of shell hardening. There are usually 2 episodes. The major episode is usually triggered by rainfall (or potentially irrigation) and a relatively minor event triggered by ‘high humidity/low light.’ Irrigation schedule, shading, and crop load also factor in.

The problem occurs when the shell, seed coat, and sometimes the shuck splits about the time of the initiation of kernel filling and shell hardening, resulting in abortion and drop of damaged fruit about 7 days after splitting. Water split is highly erratic, with incidence and severity varying depending on cultivar, location, and year. Crop loss can be severe in certain years and nearly absent in others. It occurs during the “late water stage”; a time when turgor pressure inside the nut is high and the shell is beginning to harden. This typically occurs during mid-August for susceptible cultivars growing in the southeastern U.S.

Water stage fruit-split of pecan is often a major problem exhibited by thin-shelled pecan varieties (e.g., Schley, Caddo, Oconee, Sumner, ‘Wichita’, ‘Frotcher’, and ‘Farley’) and, to a lesser degree, by certain relatively thick-shelled cultivars (e.g., ‘Cape Fear’ and ‘Elliott’).

The split is often inside the nut and you will see green nuts on the ground, which will stain a few days later. Other times when the incident is violent, you will see a longitudinal split in the shuck itself. By the time you see water split, there’s little that can be done. Crop loss to water split is minimized, but not totally prevented by managing soil moisture to minimize the severity and duration of water stress during the last two weeks of fruit sizing, and by crop-load thinning.

Certain varieties will always have a potential for it under the right conditions. It seems to be worse when there’s been a dry spell and you suddenly get a heavy rainfall or crank up the irrigation all of a sudden. This is another reason to maintain good soil moisture and minimize water stress through the entire season. Foliar sprays of B and Ni in the spring have also led to reductions in water split.”

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Filed under Disease, Entomology, Pecans

August 19, 2014 · 4:42 PM

Ultra-Late Soybeans Need Water

Here is a field of ultra-late soybeans planted after corn. They need to be planted as soon as they can right after corn is harvested, by the first week of August. These were drilled at 7.5 inch no-till drill at a high seeding rate. UGA Extension Soybean Agronomist Dr. Jared Whitaker says we need to shoot for a seeding rate of at least 175,000 seed / acre. Dr. Whitaker recommends using either a hula-hoop or a yard stick to lay out over the rows to count a 5 x 5 area for stand counts. We did a stand count this morning which showed about 180,000 plants per acre (below).

With the ultra-late system, one issue is having pods produced on lower nodes and located too low to be harvested. Irrigation and addition nitrogen help increase the height of soybean crop and potentially help increase the height of pods produced on the bottom of the plant. In any case, irrigation is a must with ultra-late soybeans. Colquitt County Ag Agent Jeremy Kichler shared this soybean irrigation chart which shoots for 45 to 50 bushel yields:

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Filed under Irrigation, Soybeans

August 18, 2014 · 8:23 PM

Algal Blooms In Ponds

We’ll notice pond water color turning a yellow-green when pollen is shed. We looked at a pond last week that had the same color but was result of phytoplankton bloom instead. UGA Extension Aquaculture Specialist Dr. Gary Burtle says this about algal blooms:

“The yellow-green color is normal for a mix of plankton found in fish ponds. The bloom shows signs of fertility, either from addition of fertilizer or from watershed runoff.

Aerial images look blue due to the reflection of light. Blue is a shorter wavelength and is not absorbed as much as red and yellow, so is reflected. Particles in the water may scatter light so that a different color is observed. However, when the particles are deep in the water, aerial photos do not capture their effect, only the blue or blue-black color. Water color can also be different from different angles, due to refraction.

The aerial photos posted on the web are taken at different seasons. One taken in the winter may not indicate a pond algal bloom, but one taken in midsummer might capture the bloom.

We recommend that visibility between 12 and 18 inches is optimal for sport fish pond management. Dense algal blooms and scums may occur when visibility is less than 12 inches. Measurements of visibility are taken at the pond surface rather than from a distance. Efforts to correlate light reflection to water quality have shown some interesting correlations, but require special filters and photographic techniques.”

Although fertilization can increase fish production significantly, it is not the best management practice for every pond. Here is a publication on Pond Fertilization & Liming from UGA Warnell School of Forest Resources.

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Filed under Aquatic Environments

August 14, 2014 · 4:48 PM

August: Critical Month For Pecans

Here is some information from UGA Extension Pecan Specialist Dr. Lenny Wells:

Some early pecan varieties have reached shell hardening and others are still approaching. This means that the water use requirements of pecan are nearing peak demand and will remain so through kernel filling. Growers should have irrigation systems running at full capacity at least by next week for most mid-season varieties like Stuart, Desirable, Schley, etc. This means 3600-4000 gallons per acre per day. Solid-set sprinkler irrigated orchards should be applying 1.5″-2″ per acre week, depending on soil type (the sandier the soil, the more water). Ideally, systems should be designed to meet these water requirements within 12 hours.

Its amazing how much water a pecan tree with a heavy crop load can use at this time. The heavier the crop, the more water required. Sure, you can still make some nuts and have a decent harvest with less water but this will maximize percent kernel, which is required for good pecan prices. If the trees don’t have a crop, you won’t have to water this much because it is the kernel-filling process that creates the enormous demand for water. Adequate irrigation at this time will also relieve undue stress on the trees, which helps them to to return a better crop the following year.