Nematodes In Centipede

Centipede Sod

Last week, we checked into some centipedegrass sod that was showing some odd symptoms. The patches of dying grass were shaped irregular and could see obvious wilting signs on the boarder. We checked for disease under the microscope and did find some however, with these symptoms, we decided to check nematodes. Here is the report below:

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CentipedeSod-NematodesUGA Extension Pathologist, Dr. Alfredo Martinez, said centipedegrass can easily be colonized by nematodes compared to other species. The report showed both Ring and Sting nematodes being above thresholds. UGA Extension Turf Agronomist Dr. Clint Waltz says at this stage it would be best to increase irrigation and fertility. When ready, harvest this grass then consider a nematode treatment prior to reestablishment.

Also, the soil test showed pH to be 4.9. Centipedegrass can take a lower pH than bermudagrass, but below 5.5 is pushing it. Research shows a pH of closer to 6.0 is better for centipede establishment. The liming will raise the pH and take effect next year. This will help increase overall fertility. Dr. Martinez also suggested using an all purpose systemic fungicides (fungicides containing thiophanate methyl, propiconazole or an strobilurin). This might help to control any facultative pathogen/saprophyte that might be lingering.

 

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Time For Pecan Leaf Sampling

Below is some infromation from UGA Extension Pecan Specialist Dr. Lenny Wells on leaf sampling for pecans:

The general recommended period for leaf sampling is July 7-August 7. I would shift these dates by about 1 week this year since crop development is running 7-10 days behind normal.

Why does it matter when you sample?

Concentrations of N, P, and Zn on a leaf dry weight basis start off relatively high early in the season, decline rapidly, reach a fairly steady state after mid-June, and then decline near leaf fall.  K tends to start high, then decreases and plateaus at about the same time as N, P, and Zn. Most of the P and Zn that accumulates in the leaves have done so by the time the leaves reach full size. Calcium (Ca) accumulates in the leaves as the season progresses, peaking in August-September. Magnesium (Mg) Manganese (Mn), and Boron (B) also tend to increase as the season progresses, but to a lesser extent than Ca.

PecanLeafSamplingHow do we sample?

  1. Collect 50- 100 middle-pair of leaflets from the middle leaf of this year’s growth (Left). Use terminal shoots exposed to the sun. Avoid twigs from the interior of the tree. Collect leaflets from all sides of the tree. Avoid leaflets damaged by insects and diseases.
  2. Abnormal trees or trees not representative of the area should be sampled separately. A complete and accurate description of abnormalities should accompany these samples.
  3. Sample trees of the predominant variety in a given block. If Schley is the main variety, sample Schley; etc.
  4. Immediately upon collection, wipe leaves (entire surface, both top and bottom) with a damp cellulose sponge or cheese cloth to remove dust and spray residue.  Do not allow the leaves to come into contact with rubber or galvanized containers. Partially air dry and place in the large envelope of the mailing kit.
  5. If recent soil test data is not available, it would be advisable to collect a soil sample and have it sent to a soil testing laboratory.  By sampling the same trees each year, growers can more readily see the results of any changes to their nutritional programs.

**Some growers have taken leaf samples throughout the growing season to determine the fertility needs of the tree. This is really unnecessary. Leaf analysis does not necessarily reflect the actual use pattern of mineral nutrients, but instead indicates concentrations of those elements in the leaf at the time of sampling. The tree knows what it needs and when it needs it.

Concentrations of mineral nutrients in the leaves change as leaves emerge, expand, and finally senesce in the fall. For many elements, the least change in concentration occurs from early July-early August.

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Peanut Disease Update

Tomato Spotted Wilt Virus 010

Over the weekend, Thomasville and most of Thomas County had more than half an inch of rain. We were checking peanuts last week, looking at 06G’s. We were seeing a little bit of tomato spotted wilt virus (above). The picture above shows the some of the classic, chlorotic ring characteristics of TSWV. It is not bad in the field, but we can expect to see some on even resistant varieties. No variety is immune.

The initial appearance of soilborne diseases such as white mold (below) is related to soil temperature, the growth of crop and rainfall/irrigation. White mold was seen less than TSWV in this field. Most peanuts have hit the 60 day mark where we generally begin spraying for soilborne diseases. Below is an update form UGA Extension Pathologist, Dr. Bob Kemerait:

White Mold 011

Very warm weather and scattered thunder storms will increase risk of several important diseaes.

1.  White mold: warm soils, increased growth of peanut crop, and rainfall have created ideal conditions for development and spread of this disease and fungicide programs should be implemented accordingly.

2.  My graduate student Abraham Fulmer is finding development of early and late leaf spot in his unsprayed peanut plots.  A further indication that it is time to spray.

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Cotton Prices

There are a lot of discussions on cotton prices dropping. Thanks to Seminole Extension Agent, Rome Ethredge for putting this together, below is some information from UGA Extension Ag Economist, Dr. Don Shurley:

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Peanut Insects On The Rise

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Dryland and irrigated peanuts are looking good throughout the county where we have received as much as 4 inches of rain on the east side over the past week and a half. This morning, we were checking for insects and disease. We started off looking at caterpillars. Our caterpillar threshold is 4 – 8 per row foot. We use the lower numbers for peanuts that may already be stressed. This is an irrigated where field is about 75% lapped and plants are growing well and healthy. We saw soybean loopers, armyworms and corn earworms at 6 – 7 worms per row foot. Since we are at high end of threshold, it is going to be sprayed.

The main insect issue we are watching for is lesser cornstalk borers. With the dryer weather, these caterpillars become a problem. The problem is more likely to be observed in non-irraged fields first. If you see a plant that is wilting serverely, slice into the shoot and try to locate the worm. Mitchell County Ag Agent, Andy Shirley, has a picture of LCB he took this week. You can see his blog post here: Lesser Cornstalk Borers.

Lesser Cornstalk Borer - Photo by Andy Shirley

Lesser Cornstalk Borer – Photo by Andy Shirley

Here is what UGA Extension Peanut Entomologist, Dr. Mark Abney, has to say:

Lesser cornstalk borer (LCB) is probably the most serious (insect) pest of peanuts in Georgia. LCB thrives in hot, dry conditions and light sandy soils. Fields need to be scouted to determine if LCB is present. When scouting for LCB, several locations should be checked in each field. The caterpillars are most easily found if you pull up the plant. Pull a few plants at each location. You will be looking for larvae, feeding damage, and silken tubes covered with soil. The larvae can be difficult to find as they will often be inside the silk tubes or inside the stems of the plant. You may also see LCB moths flushing from the peanut foliage as you walk through fields.

Granular chlorpyrifos (Lorsban 15G) is currently the only material recommended for LCB control in the UGA Pest Management Handbook. This product CANNOT be applied by airplane to peanut. Liquid formulations of chlorpyrifos are NOT REGISTERED for foliar application in peanut. Granular chlorpyrifos must have rainfall or irrigation to be effective. Chlorpyrifos will kill beneficial insects, so we should be made aware that using this product increases the risk of outbreaks of foliage feeding caterpillars and more importantly spider mites.

Additionally, previous work at UGA found foliar insecticides to be ineffective at controlling this pest. While there are several products available for use in peanut that would probably kill LCB larvae, getting the insecticide to the target will be nearly impossible. We are currently testing a variety of foliar insecticides against LCB and will provide updates if/when any new information is available.

Rainfall and cooler temperatures will slow LCB populations, but once we get into an outbreak situation, we should not expect rainfall to alleviate the problem.

 

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Pond Weeds – Torpedograss & Southern Water Grass

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Torpedograss

Torpedograss

We looked at a pond yesterday which was about 1.5 acres, spring fed and covered in some weeds. Weeds in ponds are placed in one of three categories: submersed, emersed, or floating. These weeds were coming from the bottom of the pond and sticking out, which are emersed. UGA Extension Aquaculture Specialist, Dr. Gary Burtle, helped us ID the weeds. The short weed is southern water grass which has some emergent parts and some submerged parts. The other plant is torpedograss. It is the tall grass with the panic-grass seed head.

Southern Water Grass

Southern Water Grass

Both weeds respond to glyphosate if enough of it is emergent in order to obtain a good treatment.  Dr. Burtle says one problem is that glyphosate does not seem to translocate into the underwater portion of plants as well. If the weed is submerged more than 25%, the herbicides have less effect. For this reason, tt is recommended to use a sticker/spreader adjuvant, like a crop oil. Also, stocking 10 grass carp triploids per acre after the weeds have decomposed would help.

This pond does have bass which is very risky to treat during hot time of the year. As the plants decay, fish can die from result of oxygen depletion. Instead of treating the entire pond at one time, it is best to treat 1/3 or 1/4 sections at a time.

 

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Pesticide Formulations

If you have a private pesticide license (category 10) or commercial license (category 21) and need an hour of credit, I am holding a course at the Thomas County Extension office where you can earn one hour credit in either category.

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