Category Archives: Disease

Peanuts Cracking

Dryland peanuts are coming up in the northwest part of the county. This is where we have had more rain. We’re talking about thrips, herbicides and some disease issues now. Below is a graph from UGA Extension Peanut Entomologist Dr. Mark Abney on latest thrips counts:

Thrips numbers on our traps have remained relatively steady for the last 3 weeks, though we did see a spike last week in Colquitt County. My first thrips trials are just now emerging from the ground, and I have not heard any reports of thrips control problems on early planted peanut as of today.

I have had questions this week about rates of imidacloprid for in-furrow applications. I recommend the upper end of the rate range for whichever formulation a grower is using….We should NOT be doubling the rate or cutting the rate in half. Be sure to check the label of the product you are using as rates vary by formulation.

Weed Control

We may not have as much Valor as preemerge out there since we are dry and concern of no activation. Where we have Valor on the ground with good activation (0.5 – 0.75″ within 7 days), it usually gets us through our “at cracking ” treatments until we use Cadre. If we don’t have Valor, we will need to be gearing up for our cracking spray 15 – 25 days after planting. But we only need to apply ‘cracking’ sprays if weeds have come up.

Disease Control

The only note to make is this week’s rainfall this week could help to cool soils, at least in the short term, and reduce risk to Aspergillus crown rot of peanut.

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Filed under Disease, Peanuts, Weed Science

Pecan Fungicides Begin

Young Trees

All of our pecan fungicides have begun at this point. We have lots of newer planted trees in the county, here are some being sprayed last week. UGA Extension Horticulturalist Dr. Lenny Wells says trees in the first few years need to be sprayed but not on a detailed spray program. For very young trees, a few fungicide applications in a season with some Tin is good. Once the trees approach production age, we need to add a few more sprays throughout the season and get closer to a full spray program.

Timing

In our area, we have been hit so hard with scab that we tend to get our fungicide sprays out real soon. Dr. Wells always says we can wait a little longer than we do. He was down last week looking at a fertilizer situation, and we looked at trees around that were leafing out at different times. He explained the issue with spraying early is not having enough leaf area for the fungicide to contact.

The most difficult part is managing orchards for more than one cultivar, which all are pretty much the same. If Desirables are in the orchard, we have to begin spray on their schedule since they are more susceptible for scab. If an orchard doesn’t have desirables and mostly Stuart, you can wait until those leaves come out. Here is a few pictures of optimum fungicide initiation Dr. Wells and I looked at in an orchard last week.

Left – This is time to spray Desirable
Right – This is too early for Desirable

Optimum time to initiate Stuart fungicide sprays

Fungicide Schedule

Below is an 8-spray fungicide schedule from UGA Extension Horticulturalist Dr. Lenny Wells provided as an example to use for pecan scab management in light of emerging scab insensitivity issues surrounding some fungicides. Since Tin is an integral part of our fungicide arsenal for pecans, and we do see some orchards with insensitivity to Tin, we are recommending saving any Tin sprays for the nut scab period since this material is better on nut scab than it is on leaf scab.

1. Absolute

2. Tebuconazole+Topsin M+Phosphite

3. Absolute+Phosphite

4. Elast/Tin

5. Absolute

6. Elast/Tin

7. Elast/Tin

8. Elast/Tin

If rainfall during the growing season is excessive, more than 8 sprays will be required for management of scab on susceptible cultivars. Therefore, the following program serves as an example of how to accommodate this need:

1. Absolute

2. Tebuconazole+Topsin M+Phosphite

3. Absolute+Phosphite

4. Elast/Tin

5. Absolute

6. Elast/Tin

7. Elast/Tin

8. Quadris Top

9. Elast/Tin

10. Elast/Tin

These examples serve only as two possible options for fungicide programs to manage scab. Many more could be developed. If an orchard has a documented high level of insensitivity to any of the fungicides listed above, the grower should contact one of the UGA Extension for specific recommendations.

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Disease & Nematode Management Considerations For 2017 Peanut Planting

Peanut growers can use a different products at planting time for the management of diseases and nematodes. Decisions as too what product to use over another, or to use a product at all, can be very confusing. Fighting seedling disease used to be simple- all growers used a fungicide seed treatment, and if they wanted some “stand insurance” they could also spray Abound in-furrow. Today, in-furrow applications are important considerations for the management of tomato spotted wilt, seedling diseases, Cylindrocladium black rot, white mold, and nematodes, not to mention thrips! Below are management options for the growers put together by UGA Extension Pathologists Dr. Bob Kemerait, Dr. Tim Brenneman and Dr. Albert Culbreath:

Note: The rates provided here are on a “per/A” basis. Typically, the full rate can be placed in single rows; the rate is typically halved per twin row. For example, Abound, 6.0 fl oz/A in-furrow for single rows becomes Abound, 3.0 fl oz/A in each of the twin rows:

Management of Tomato Spotted Wilt

Tomato Spotted Wilt Virus

A number of products can be used to manage thrips on peanuts. However, only one product, Thimet (ai: phorate) is effective in reducing the risk to this disease. The reduction in risk to tomato spotted wilt is not related to the thrips control that it provides, rather is seems to be associated with the response of the plant to Thimet. Thimet likely activates defense-response genes in the peanut plant that help to protect the plant from the virus. Growers who want to plant early (before May 1), or who want to use cultivars with spotted wilt risk points greater than those of Georgia-06G, might especially want to consider to using Thimet for management of tomato spotted wilt.

Management of Seedling Diseases

Peanut seed and young seedlings are susceptible to attack from a number of fungal pathogens. The two most important fungal pathogens causing death of peanut seedings in Georgia are Rhizoctonia solani and Aspergillus niger. Fungicide seed treatments are a critical tool to manage seed rots and seedling diseases; currently nearly all seed is treated with Dynasty PD. Dynasy PD is composed of azoxystrobin, fludioxonil, and mefenoxam. However, growers can also protect the developing plants from seedling diseases with in-furrow fungicide applications of fungicides like Abound (5.7-11.4 fl oz/A), Proline (5.7 fl oz/A), and Evito (2.3-3.5 fl oz/A). These fungicides are typically used to compliment seed already treated with a fungicide seed treatment.

Aspergillus Crown Rot

The most effective in furrow spray for stand establishment has been Abound, although Proline also has activity on these pathogens and Evito is labeled for this use as well. The benefits of these products have not been as consistent in recent years, and research is underway to determine the factors involved.

Management of Cylindrocladium black rot (CBR) and early-season white mold

Proline (5.7 fl oz/A) applied in-furrow has been an important treatment for the management of CBR. Though this disease has been less widespread in recent years, an application of Proline in-furrow is still useful where there is a threat of CBR. When favorable conditions, such as very warm weather, occur early in the season, in-furrow applications of Proline also offer some protection from early-season white mold. The extent of the protection is likely less than that provided by banded applications of Proline 3-5 weeks after planting. Decisions to use Proline in-furrow should be made based upon a) risk to CBR, and b) risk to early-season white mold (although there are effective alternatives for white mold).

Mycelium and sclerotia (yellow bee bee’s) from white mold

Management of Nematodes

Nematode-resistant cultivars continue to hold up well against even high populations of root knot nematodes. However, growers electing to plant a susceptible cultivar like Georgia-06G in fields infested with the peanut root-knot nematode should consider the use of a nematicide. Popular nematicides for peanut production in Georgia include Telone II (4.5-6 gal/A), Velum Total (18 fl oz/A) and AgLogic 15G (7 lb/A). To prevent injury to seed and seedlings, fumigation with Telone II should occur 10-14 days prior to planting and when soil conditions are not too dry (powder) nor too wet (mud). Fumigation with Telone II can provide excellent control of nematodes but DOES NOT control thrips. Growers who use Telone II must still apply something for management of thrips.

Velum Total is a combination of fluopyram for management of nematodes and also imidicloprid for management of thrips. Growers who use Velum Total do not need to add any additional thrips control product in the open furrow. (Note that imidicloprid does not reduce the risk to tomato spotted wilt.) Also, use of Velum Total does provide additional early-season management of leaf spot diseases. The extent of this protection from leaf spot is such that growers should be able to skip the 30-day after planting fungicide application for leaf spot, unless they have planted a very susceptible cultivar like ‘Georgia-13M’ or TUFRunnerTM’511’.

A question that often arises is, “If I use Velum Total, do I get any protection against seedling diseases as well?” The “bottom line” to this question is that use of Velum Total should complement a seed treatment and be good “stand insurance” and we would not add anything else. The biggest factor by far to reduce the impact of seedling disease is the quality of the seed and putting that seed in the right soil conditions at the right time.

AgLogic 15G (7 lb/A) is for management of thrips and nematodes. AgLogic does not reduce the risk to tomato spotted wilt. The rate is lower than what was historically used for Temik 15G (10 lb/A). Additional research is needed to assess the efficacy of the 7 lb/A rate on management of nematodes. In high risk field it may be advisable to use a combination of these nematicide options.

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Implications Of Bacterial Boll Rot

At our Georgia Association of County Ag Agents (GACAA) meeting, we get to see presentations and posters of work done around the state. I wanted to share this poster done by Holly Anderson in Ben Hill County, EVEN THOUGH our conditions this year were as less conducive for boll rot as they have been in a long time.

We’re normally wet in our area and this is a concern of many growers. Dr. Kemerait always has points about boll rot, but it is unavoidable if cotton is subjected to prolonged periods of wetness and humidity late in the growing season. This project shows the progression of boll rot from infection to harvest and potential losses.

implicationsofbacterialbollrot-holly

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December Row Crop Disease Update

A few things to think about with regards to disease and nematode management in preparation for the 2017 field season.

La Nina:  Our UGA Extension climatologist Pam Knox has good information available on our current conditions, but here are my thoughts:

We are currently in a “weak” La Nina situation, “weak” because the equatorial waters of the cost of Ecuador are more than a half degree COOLER than normal.  As best I can tell, the waters have been about 7/10 of a degree cooler which barely qualifies as a La Nina (as opposed to last year where we had a robust and sure-enough El Nino).  So what does this mean? During La Nina years, the Southeast tends to (“tends to” means more often than not, but not always..) experience warmer and drier winters. Because we have a weak La Nina, this forecast could change.

Pigweed seedhead in broccoli before Thanksgiving. We are yet to have frost to knock back pigweed growth.

Pigweed seedhead in broccoli before Thanksgiving. We are yet to have frost to knock back pigweed growth.

How does our current “La Nina” impact our recommendations?

  1.  Drier is not a good thing as it may mean we don’t fill up irrigation ponds for next year.  It my mean we have a lot of trouble establishing cover crops this fall.
  2.  Warmer temperatures may mean that kudzu, volunteer peanuts, corn, cotton-regrowth, etc. pathogens (like those that cause soybean rust and southern corn rust) may survive and increase longer than they would with an earlier “killing” frost.  Also, as long as the crops and volunteers are active in the field, nematode populations can continue to increase and build.  This will lead to larger populations for next season. Once the plants are killed, the nematodes can no longer feed. Once soil temps drop below 65F, the activity of the todes drops off as well.
  3.  We may get some very cold weather soon, so we may not need to worry that much; however the general prediction is that we will have a warmer winter.
  4.  The weather this winter will have some effect on TSWV and insects for next year.  It remains to be seen what and how… but it will impact them.

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Filed under Corn, Cotton, Disease, Peanuts, Soybeans, Weather

Bermudagrass Leaf Rust

aliciabermuda-leafrust-010

It’s not unusual for us to be dry in October. But it is unusual to go into October already dry. Many folks have not seen one measurable rain in the month of October. As we walked through this Alicia hay field, our boots were covered in rust spores. Clouds of rust were seen with each step. Leaf rust this time of year is pretty typical in Alicia. We may not see it exactly this bad with Coastal.

Identification

Will rust, you will see red to orange lesions on the leaf and stem. Look for a raised area or blister which is the rust postules like we see in wheat and corn. Rubbing your finger over the leaf will leave a rusty color.

Leaf Rust

Leaf Rust

Leaf Rust

Postules of rust are raised

Management

We cannot use fungicides on our hay fields, so management is strictly avoidance. Coastal, Tift 44, and Tift 85 have some level of resistance while Alicia is extremely susceptible. But even less susceptible varieties are infected with leaf spot when POTASSIUM is low. Most reported leaf spot cases are directly related to low soil potash. Nutrients are removed from bermuda hay fields in about a 4-1-3 ratio of N, P2O5, and K2O with harvest. We need 75 percent as much potash as nitrogen  applied each season. Split applications of K are better in sandy soils. In these cases, nearing the end of the season, we need to go out with another shot of straight potassium.

Visit Leafspot Diagnosis and Management in Bermudagrass Forages for more information.

Leaf rust on boots

Leaf rust on boots

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Filed under Disease, Fertility, Forages

Peanut Harvest & Row Crop Disease Update

Boston Peanut

Boston Peanut

Golden Peanut in Meigs

Golden Peanut in Meigs

After afternoon showers and rain last week, we are really getting back to picking this week. Growers are also wide open on defoliating cotton. I saw some cotton being picked yesterday.

I visited our buying points this week and looked at grades and other issues. Thankfully, we are not having many Seg 2 burrower bug hits as last year and the year before. Between both buying points, I only know of one known burrowing bug Seg 2. In every other Seg 2 case, they’ve turned around and cleaned them and they were fine.

Grades are probably a little down this year compared to last, but are definitely not bad. Many good grades overall and low percentage of our sound splits and other kernels (pops). We could be pulling the trigger early on the some of the fields. Almost all growers are checking maturity twice in fields before digging, and many have checked more than two times. We’ve not seen maturity develop at a normal pace with our dryland peanuts which has made digging decisions tough. With more peanuts in the ground, growers are having to dig when they have help, or wagons are available, or weather permits. Vine condition is also a factor in our decision at this time. Overall, we’ve had good harvest conditions this week. Even with afternoon storms or showers, sunny days have been able to dry peanuts quickly.

Collecting grading samples at Boston Peanut

Collecting grading samples at Boston Peanut

UGA Extension Pathologist Dr. Bob Kemerait has this information on current disease issues:

Peanuts

Harvest is well under way by this time, but disease issues still affect peanuts that won’t be harvested for another three weeks or more. I have seen some fields where harvest is approaching and where white mold (stem rot) is still active, and I have recommended growers late in the season apply a mixture of tebuconazole and chlorothalonil to finish the season (both products have a 14-day preharvest interval). Other white mold products could also be applied (check preharvest interval first), but with time running out in the season, the value of tebuconazole is certainly a consideration.

Late Leafspot

Late Leaf Spot

I have also observed where leaf spot, especially late leaf spot, is aggressive late in the season, primarily on a susceptible variety like ‘Georgia-13M’. If less than two weeks to go before digging, it is doubtful anything should be applied (or legally can be applied). If peanuts are 30 days or more away from harvest, then the grower can mix a pint of chlorothalonil with 5.5 fl oz/A of Alto. If harvest is more than 14 days away from harvest, the grower can mix 5-10 fl oz/A Topsin with a pint of chlorothalonil. Fields where defoliation from leaf spot diseases has reached 50% or more and have not yet reached the optimal digging date should be considered for an early digging.

Soybeans

Soybean producers in southern Georgia have experienced losses to Asian soybean rust this year; however it appears that most have successfully protected their crop with judicious fungicide applications. MORE IMPORTANTLY, I have observed a SIGNIFICANT amount of frogeye leaf spot (Cercpospora sojina) disease in a number of fields this year; something I have not seen in many years. I am not sure why this is so; however it is something we will need to watch again next season as well. Additionally, I am seeing pre-mature defoliation to Cercospora blight (Cercospora kikuchii) in a number of fields; this disease often results in purple stain of the soybean seed. Cercospora blight is diagnosed, in part, by the prominent loss of leaves in the top of the plant leaving only the petioles, reaching like bony fingers to the sky.

Cotton

Bacterial blight (Xanthomonas citrii pv malvacearum) continues to cause concern to many growers in the state. From your reports, reports from our consultants, and from my own observations, it is clear that bacterial blight can be found in a number of fields across the Coastal Plain. Classic symptoms or bacterial blight on leaves, bracts, bolls, stems and petioles are fairly easy to diagnose; still symptoms of other diseases may inadvertently be diagnosed as “bacterial blight”. 

It is my belief, based upon my observations and discussions with a number of experienced individuals, that losses to this disease are likely to be small and even negligible in many fields. Finding a little bit of disease in a field is an important contribution to understanding the occurrence of bacterial blight in 2016; but incidence alone does not mean significant yield loss.

Certainly there are some fields, especially in extreme SW Georgia, were boll rots appear to be closely associated with bacterial blight and losses are likely to occur. Effective management of bacterial blight by a grower revolves around variety selection (we are composing such a list for Georgia cotton producers now) and management of crop debris/residue as the pathogen can overwinter in such. Crop rotation and burying of crop debris can help to minimize the development and spread of the disease in upcoming seasons.

Bacterial Blight

Bacterial Blight

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Filed under Cotton, Disease, Peanuts, Soybeans