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Louisiana Rice Notes #3

Louisiana Rice Notes #3 published on No Comments on Louisiana Rice Notes #3

A new Louisiana Rice Notes newsletter is now available. This edition covers the recent heavy rainfall and pending storms, nitrogen fertilizer questions, conventional rice following Provisia, Louisiana variety and hybrid trends over the last 18 years.

2019 Louisiana RIce Notes #2

2019 Louisiana RIce Notes #2 published on No Comments on 2019 Louisiana RIce Notes #2

This editions covers the reasons for the poor rice germination and poor stands we are seeing, things to consider prior to fertilizing and flooding, and why fertilizing on dry ground is so important.

Soybean Variety Response to Taproot Decline (TRD)

Soybean Variety Response to Taproot Decline (TRD) published on No Comments on Soybean Variety Response to Taproot Decline (TRD)

Trey Price, Associate Professor, & Myra Purvis, Research Associate, Agronomic Crop Pathology, Macon Ridge Research Station

Boyd Padgett, Professor, Agronomic Crop Pathology, Dean Lee Research Station

Taproot decline (TRD) of soybean, caused by Xylaria sp., usually is not noticed until pod fill when interveinal chlorosis and necrosis (Figure 1) become evident from the turn row.  However, the disease may cause seed rot, seedling disease (Figure 2), and plant death (Figure 3) at any point the growing season.  Infected seedlings and vegetative stage plants usually go unnoticed because they are quickly covered by rapidly growing neighboring plants.  Infected plants will break at the soil line when pulled.  Roots will appear black when excavated (Figure 4), and are usually in contact with blackened debris from the previous season.  Reproductive structures of the pathogen known as “dead man’s fingers” may appear at the base of affected plants or on other debris during periods of high humidity producing spores that resemble powdered sugar (Figure 5).  Disease distribution within the row usually will have a focal point of dead plants, surrounded by those with foliar symptoms, and neighboring healthy plants.  These areas may overlap creating a clustered and streaky distribution within a given field.  Fields in soybean for two years or more are at risk to taproot decline, and yield losses can be significant.  For more information concerning taproot decline, please read the first report at the following link: https://doi.org/10.1094/PHP-01-17-0004-RS.

Figure 1. Interveinal chlorosis and necrosis.
Figure 2. Taproot decline of seedling.
Figure 3. Plant death caused by taproot decline.
Figure 4. Blackened root diagnostic of taproot decline adjacent to infested debris.
Figure 5. “Dead man’s fingers” produced by Xylaria sp., causal agent of taproot decline.

Many requests for a list of susceptible/resistant varieties have been received prompting the release of preliminary data.  During the past two off-seasons in the greenhouse, we have challenged varieties from the 2016 Official Variety Trials against the pathogen, Xylaria sp.  The process is briefly described hereafter.  We used sterilized millet infested with the pathogen to infest growing medium.  Inoculum was standardized using inoculum concentration experiments (data not shown).  A total of 145 varieties were screened.  During each “run”, 4 replications of 40 varieties (4 seed/4” pot, planted in a linear furrow) were either inoculated at planting or left non-inoculated then removed to flood-irrigated greenhouse tables for three weeks.  Plant roots were harvested, dried to final moisture, and weighed.  The experiment was repeated once, and paired t-tests (α=0.05) were used to compare inoculated (n=8) vs. non-inoculated (n=8) root weights for each variety.  For simplicity, we present the results here as the percentage of root weight reduction.

Paired t-tests indicated that significant root weight reduction occurred at 48% and higher.  Based on percent root weight reduction, varieties were divided into four categories: susceptible (>48%), moderately susceptible (36-48%), tolerant (24-36%), and resistant (<24%).  Out of 145, 97 varieties were deemed susceptible with percent root weight reduction ranging from 48 to 85%.  There were 25 moderately susceptible, 16 moderately resistant, and 7 resistant varieties.  For brevity, we will not present the susceptible varieties in this report.  A list of all varieties included in the screening can be found here.  Resistant, tolerant, and moderately susceptible varieties with corresponding percent root weight reduction are in Tables 1, 2, & 3, respectively.  Field confirmation of these results is ongoing.  Preliminary data from inoculated field trials indicates that varieties deemed resistant in the greenhouse show no significant response.  Varieties deemed susceptible in the greenhouse show significant responses to inoculum in the field.

Table 1.  List of TRD-resistant varieties as determined by inoculation and response.

Variety % Root Weight Reduction
OSAGE 8.391702
CZ 4818LL 18.879462
5N490R2 19.263012
S42RY77 20.944016
5N433R2 22.215409
5067 LL 22.559704
R07-6614RR 22.970824

Table 2.  List of varieties moderately resistant to TRD as determined by inoculation and response.

Variety % Root Weight Reduction
Armor 55-R68 25.253945
RJS47016R 25.793535
CZ 5375RY 26.205598
HBKLL4953 27.339808
4880 RR 27.926596
P5752RY 28.094408
CZ 5225LL 28.605468
ARX4906 29.805397
Go Soy IREANE 30.762175
4995 RR 30.883269
AG 48X7 31.611326
P4788RY 32.46393
AG 46X6 34.502577
S47RY13 35.157094
5625 RR2 35.190462
S49XT07 35.483918

Table 3.  List of varieties moderately susceptible to TRD as determined by inoculation and response.

Variety % Root Weight Reduction
P4814LLS 36.6288
CZ 4105LL 36.631044
GS48R216 37.120729
REV 57R21 37.152585
CZ 4222LL 37.789292
S49LL34 39.360691
P54T94R 39.928806
S12-2418 40.28502
S52RY77 40.607899
REV 51A56 40.734935
P41T33R 41.997581
S11-17025 43.578124
4967 LL 43.925284
S47-K5 43.984519
Armor 46-D08 44.015611
Armor 48-D24 44.107678
Go Soy 5115LL 44.470801
Armor 48-D80 45.47956
REV 56R63 45.566353
REV 49R94 45.659963
Rev 49L49 45.896947
S43RY95 46.122564
5N480R2 46.84488
5N406R2 47.288423
P4588RY 47.58291

In addition to variety selection, data from research trials, numerous observations, and other anecdotal accounts indicate that tillage and/or rotation will reduce TRD incidence and mortality.  To date, there are no recommended seed treatments for taproot decline.  Ongoing research indicates that a few fungicides applied in-furrow at planting may be effective on the pathogen.  Taproot decline is soil/debris borne; therefore, avoiding spread via equipment is recommended.  More research is needed to develop and further refine management strategies for taproot decline.

For more information on these topics or others, please contact your local extension agent, specialist, nearest research station, or visit www.lsuagcenter.com or www.louisianacrops.com.

Louisiana Granted Special Local Needs (SLN) Renewal for 2 lbs Ai/Acre Seasonal Use Limit of Acephate in Soybeans

Louisiana Granted Special Local Needs (SLN) Renewal for 2 lbs Ai/Acre Seasonal Use Limit of Acephate in Soybeans published on No Comments on Louisiana Granted Special Local Needs (SLN) Renewal for 2 lbs Ai/Acre Seasonal Use Limit of Acephate in Soybeans

Louisiana has received a renewal of the 24(c) special local needs label that increases the seasonal use rate of Acephate from 1.5 lbs Ai/Acre to 2.0 lbs Ai/Acre in soybeans. Information pertaining to use rates, application restrictions and timings can be found on the specific cropping label.  The label is available in the link below. The label must be in possession of the user at the time of application.  If you have any questions please contact your county agent or extension specialist for more information.

Acephate SLN Label

GGreen Bean Syndrome Caused by Threecornered Alfalfa Hopper

Threecornered Alfalfa Hopper Threshold in Louisiana

Threecornered Alfalfa Hopper Threshold in Louisiana published on No Comments on Threecornered Alfalfa Hopper Threshold in Louisiana

Over the past week, I have received a number of phone calls pertaining to what economic threshold should be used for Threecornered Alfalfa Hoppers (TCAH) in soybean.  Based on previous work conducted by Sparks and Newsom (1984), Sparks and Boethel (1987) and subsequent experiments conducted by the LSU AgCenter in the last five years, the LSU AgCenter recommended threshold is “starting at pod set, 3 nymphs per row foot or one adult per sweep”. This recommendation is based on published data and experiments conducted in Louisiana at LSU AgCenter Research Stations and Louisiana field locations.  Independent of yield loss, TCAH can also cause an increase in the “green bean/stem syndrome” that often is present in soybean fields. Green bean syndrome’s exact cause is not known but we do know that stress plays a large part in the malady. Environmental stress compounded by insect or disease related stress is often the culprit. The picture below is from a TCAH experiment conducted at the Macon Ridge Research Station to investigate the effects of TCAH on dryland soybeans.  The experiment was terminated at the onset of stink bugs and all non-target insects were controlled for the duration of the experiment. The green bean syndrome pictured below is directly related to TCAH feeding. The beans on the left were non-treated throughout the duration of the experiment, the beans on the right were keep free of hoppers. We also observed significant increases in green bean syndrome in both irrigated and dryland soybeans and observed significant differences in yield in dryland soybeans but not irrigated. The take home message is TCAH are economically important insects that have a documented, data backed economic threshold of 1 adult per sweep at pod set. If you have any questions or concerns feel free to contact your county agent or me for more information.

GGreen Bean Syndrome Caused by Threecornered Alfalfa Hopper
Green Bean Syndrome Caused by Threecornered Alfalfa Hopper

Louisiana Rice Notes #6

Louisiana Rice Notes #6 published on No Comments on Louisiana Rice Notes #6

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This edition covers early rice yields in southwest Louisiana, ratoon stubble management, sheath blight, AV-5055 headed rice bird repellent, LSU AgCenter seeks hybrid rice seed partner, and how to join the text message group. This edition and older editions can be found on the LSU AgCenter’s Rice website here:

http://www.lsuagcenter.com/topics/crops/rice/field_notes