Monthly Archives: July 2014

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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Peanut Insects On The Rise

Peanuts 003

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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Filed under Disease, Entomology, Peanuts

Pond Weeds – Torpedograss & Southern Water Grass

Torpedograss/SouthernWaterGrass 003

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.

PesticideCredit

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Peanut Water Requirements

Peanuts-Rain 002

The high amount of rainfall during our peanut planting window caused growers not to get their peanuts planted until mid-to-late May. We now face a higher water use period falling in time with less rain period. We have be getting scattered showers in the afternoons, but not enough to provide the water we need. To make sure the crop has enough water UGA Extension Scientist, Dr. Gary Hawkins, has the chart below representing water use throughout the growing season.  This indicates what peanuts need at different maturities and can also be used as a guide to how much water is needed.

We need to also be aware that soil type has an impact on the amount of water available to the crop.  For sandy soils, a high intensity rain will likely infiltrate and may provide needed water, however, in heavier soil, the same intensity rainfall will potentially have high losses due to runoff because it will not be able to absorb the water as well as the sandy soil. On the other hand the heavier soils have a higher water holding capacity and will retain moisture for longer than sandy soils.

PeanutWaterUse-Dr.Hawkins

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Filed under Irrigation, Peanuts

Kudzu Bug Thresholds

Soybeans 002

Soybeans are in the county are flowering now moving into the reproductive (R6) growth stage. I got reports last week of kudzu bugs and found some Monday. According to UGA Extension Entomologist, Dr. Phillip Roberts, kudzu bugs populations have been lower in the state overall this year.

Adult Kudzu Bug

Adult Kudzu Bug

We still want to watch for nymphs but try not to spray tooearly. At least two generations occur each year; it takes 6 – 8 weeks for a kudzu bug to complete its lifecycle. Because of this, spray timing should interrupt the development of lifecycle by targeting immatures. The threshold is one nymph per sweep or many nymphs present visually.

KudzuBugThreshold

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Filed under Entomology, Soybeans

Sweet Corn Production Workshop

Mr. Calvin Perry at Stripling Irrigation Research Park in Camilla is holding a Sweet Corn Production Workshop  on Tuesday, July 22.

Here’s the tentative schedule for the Workshop:

9am – Welcome (Calvin Perry)

9:10am – Fertility and Varieties (Dr. Tim Coolong)

9:30am – Insect Management (Dr. Stormy Sparks)

9:50am – Weed Management (Andy Shirley)

10:10am – Weather Station Network (Dr. Ian Flitcroft)

10:30am – Break

10:45am – Irrigation Management including Drip (Dr. Gary Hawkins)

11:05am – Previous Irrigation Management Projects, Soil Moisture Sensors (Rad Yager)

11:25am – Precision Ag, Soil Mapping, Etc. (Dr. Wes Porter)

11:45am – Food Safety, Sanitation Management (Dr. Bill Hurst)

12:05pm – Lunch

**For lunch arrangements, we will need to get a head count by Thursday, July 17. Please RSVP by that date.

Note – we are in the process of requesting CCA ceu credits.

If you have any questions, contact SIRP at:

Phone 229-522-3623

Email: perrycd@uga.edu

Web: www.striplingpark.org

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