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.
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:
This edition covers early harvest returns, hot weather, N fertilization timing and sources for the ratoon crop, and how to join the text message group. This edition and older editions can be found on the LSU AgCenter’s Rice website here:
Over the past two weeks Louisiana has experienced a slow but steady corn earworm moth flight in cotton, which has lead to a slow but steady egg lay. Fortunately, this type of worm activity has not put the selection pressure on our Bt technology we experienced last year. This has also drastically reduced our insecticide oversprays as well. As of this week, Louisiana has more cotton that has not been sprayed for bollworms than cotton that has been sprayed.
Based on small plot research and Bt sentinel plot work from the Louisiana cotton growing areas, all of the technologies are performing better this year than last year. Results from our Bt technology tests indicate Bollgard 2 varieties are experiencing an average of 2.5% fruit injury, Bollgard 3 varieties are experiencing an average 3.0% fruit injury, both Widestrike and Widestrike 3 varieties are experiencing 4.0% fruit injury. TwinLink and TwinLink Plus are experiencing 5.0% and 3.0% fruit injury respectively. These numbers are also reflected in reports I am receiving from the field with only a few instances of rescue sprays needed for bollworm escapes in Bt cotton. Remember, the fruit injury threshold for Louisiana cotton is 6% with the presence of live worms.
Overall, this is good news for Louisiana cotton producers and signals that our Bt technology may still have some life left in it. Beware, this situation can change quickly and bollworm escapes can and will happen in all technologies. Scouting is key and under light pressure our Bt technology is appearing to hold but if pressure intensifies a rescue spray may be warranted. Keep in mind that bollworms are cryptic feeders, and worms that have established in squares and bolls may not be controlled by insecticides including the diamides. If you have any questions or comments, please feel free to contact your county agent or me.
Please see this post on top death in field corn by Dr. Dan Fromme: LSU AgCenter Corn, Cotton and Grain Sorghum Specialist.
We all know that as a corn crop progresses toward physiological maturity, the leaves naturally begin to senesce (die). The timing and pattern of leaf senescence are genetically regulated but are also influenced by environmental triggers, including sever photosynthetic stress. This year, where much of the grain fill period has experienced severe drought and/or heat stress, the onset of leaf senescence can occur earlier than expected prior to kernel black layer. This means leaves begin to die sooner than expected, and the leaf pattern of leaf senescence sometimes changes.
Most often the leaf pattern of senescence that we see in most years is one where leaf death begins at the bottom of the plant and slowly moves up toward the upper leaves. However this year, due the late season stress, leaf senescence is progressing from both the bottom and the top of the plant with green leaves remaining in the middle of the plant for some time until complete leaf senescence occurs. Also, these fields appear to cause an unusual golden glow in the upper canopy against the morning or evening sun. The impact or effect on grain yield will depend on how early in the grain filling period the death of the upper leaves occurs. This year, we might see some test weights on the low side.
Citations: Nielson, R.L., Top leaf death or dieback in corn .2011. Purdue University Department of Agronomy.
This edition covers upcoming field days, crop update, disease management, rice drying and rice irrigation survey results, a new channeled apple snail survey, 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
The third edition of Louisiana Rice Field Notes for 2018 is now available. This edition covers planting progress, DD50 heat units, stunted rice, rice seed and seedling diseases, channeled apple snail damage, Loyant herbicide use, and a consultant quiz. Older editions can be found on the LSU AgCenter’s Rice website here: http://www.lsuagcenter.com/topics/crops/rice/field_notes
The newest edition of Louisiana Rice Field Notes for 2018 is now available. This edition covers planting progress and the potential effects of cold weather and wind on rice germination and seedling development. Older editions can be found on the LSU AgCenter’s Rice website here: http://www.lsuagcenter.com/topics/crops/rice/field_notes