Early Wheat Planting Insect and Disease Vector Management Suggestions for the 2022-23 Wheat Crop

 

Early Wheat Planting Insect and Disease Vector Management Suggestions for the 2022-23 Wheat Crop

Blayne Reed, EA-IPM Hale & Swisher

Edit by Dr. Pat Porter, District 2 Entomologist

                With rains finally blessing the High Plains area, and with grain prices rising, many producers will likely want to take advantage of the soil moisture for wheat establishment right away.  It has been so dry for so long in our semi-arid region we certainly recommend taking advantage of moisture opportunities, especially for dryland acres.  The seed availability issues of this year aside, crop establishment is always the first major hurdle in Texas High Plains wheat production.  Starting wheat early is especially pressing for operations with cattle in the mix who must have wheat for grazing well established before a hard freeze date.  While it is by far our largest concern, moisture is not the only issue we need to address before heading to the field with the wheat drill.  In fact there are a lot of disease and pest issues that, if not addressed during pre-planting can, and often do, cause wheat in our region to fail.  Unfortunately, any of these issues are multiplied for winter wheat when it is planted early. 

                These issues, at least the ones we can usually expect, revolve around the green bridge for insect and other pests that exists between our summer crops and native plants to our winter plants if they are established before a killing freeze.  Insect pests and other plant disease carrying vectors are thriving during late summer and fall.  There are several species, and not even all of them are insects, but they are usually those pests with piercing-sucking mouthparts that spread plant diseases much like mosquitoes spread disease in mammals.  Species like greenbugs, many other aphids, and mites are often the culprits here.  If given the opportunity and if the pest has a wide host plant range, these species will certainly jump from summer host to winter crop as their summer hosts dry down, often carrying a plethora of plant diseases with them which can devastate wheat. 

We don’t usually notice these diseases in our native pastures, weeds, or even most summer crops as those species are either not susceptible to the disease or are resistant to them in some way.  When the disease is transferred to the winter crop, these disease vectoring pests move across the fields generationally spreading these diseases as they feed.  Usually this feeding is sub-economic on its own, but once the host plant is infected with a disease it is susceptible to, the disease will take hold.  For most wheat production fields infested with a virus such as wheat streak mosaic, or many of the other similar plethora of hard to identify viruses or pathogenic diseases, we might not notice disease symptoms until the next spring once jointing begins. By then it is far too late to do anything about the issue.  In this case there is no treatment I am aware of that can even help with the symptoms, and harvest might even become impractical if the disease infection is severe enough, if there are multiple disease infections in play, or if amplified by environmental conditions. 

So, how do we need to address this issue?  We need to break the green bridge somehow.  Waiting to plant winter wheat until after a freeze has proven to work.  Here we wait until and all green life is gone from the summer crops in the area before planting our wheat.  This option costs nothing without hurting yield, if moisture is available to establish later, and denies the insect vectors a chance to settle into the winter crop until it is too late for them to establish.  Most of the pests in question are either dead for lack of a host or have found somewhere else to complete their life cycle by the time this later planted wheat emerges, thus preventing the pests from ever transmitting the disease directly into your new wheat fields.  Year in and year out for my wheat scouting, the later planted fields typically have a lower disease occurrence.  This does fail to establish grazing for cattle that need grazing fully established before a freeze.  More importantly today, it certainly does not take advantage of available rainfall moisture during a drought when moisture is never even promised, let alone guaranteed. 

So, the next best option for preventing this issue while making use of the current moisture seems to be making use of insecticidal seed treatments, and most times, fungicidal seed treatments.  These do come with a cost, just at a time when producer’s cash flow is at its lowest, but the cost is light compared to the likely returns.  It should also be said these treatments do nothing for mite pests, only insects.  Seed treatments also do not prevent the insects from moving into the field across the ‘green bridge’ but rather kills them soon after they move in and begin to feed, stopping the spread of disease at the initial point of entry, usually limiting disease exposure to a short border line or small pockets in the field. 

The winter wheat crop of 2021 - 2022 lacked in many things.  But a photo is worth a thousand words.  The top photo is of a dryland field planted in the first week of September 2021 and used insecticidal seed treatments.  The bottom photo is from a different producer’s dryland field with its southeast corner about 40 yards from the northwest corner of the top field.  The bottom field is of the same variety and planted the same week but without seed treatments.

2021-22 dryland wheat with insecticidal seed treatment

 

 

2021-22 dryland wheat without insecticidal seed treatment

 

Neither field is ideal, but this does show what seed treatments can do for early planted wheat.  These photos were both taken during the last week of March 2022 moments apart.  Note on the seed treated field the edge, where the insect pests moved from the summer grasses in the ditch, and the few holes in the field, likely where insect pests flew from summer crops and landed and established before the freeze last year.  These blank areas were infected by the disease vectoring insects, but they did not spread across the whole field.  In the multiplication impact of the drought, the wheat in the disease affected areas finally desiccated and died, while the majority of the field survived meagerly to at least offer some spring grazing and/or limited yield.  Across the road in the non-seed treated wheat, we see the same pattern start where the insects first established and infected the plants back in the fall, but nothing stopped the disease vectoring pests from spreading the diseases across the whole field.  In the drought stressed 2021-2022 season, this field turned into a total loss.  Unfortunately, the bottom field represented far more acres than the top did last year. 

We might be in something of a dangerous situation today with a desperate need to plant our winter wheat early to take advantage of some soil moisture.  Plainly the disease pressure in our environment is very high.  I am afraid that if our potentially early planted wheat gets exposed to this level of disease pressure without protection from seed treatments, we could be facing another failure in wheat production in the Hale and Swisher area again next year, even if the drought situation subsides.  I strongly recommend looking into the insecticidal seed treatment options available to wheat producers this year.  I have not tested, noted, or recorded a difference in seed treatment brands.  Today I feel strongly that all of them will outperform untreated seed.  While I have not tested it either, I have noted that insecticidal seed box treatments perform very well too.  I sense that these seed box treatments might not be as even or potent as on-seed treatments, but they seem in my scouting observations to be well worthwhile and a close second to the on-seed option if this is the best option for naked seed that needs to be in the ground this week. 

Please call our Plainview office with any questions or concerns.

Blayne