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Neonicotinoid insecticides losing efficiency in potato psyllid control

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By: Kay Ledbetter

AgriLife Research study shows biological control may help

Writer: Kay Ledbetter, 806-677-5608, skledbetter@ag.tamu.edu
Contact: Dr. Ada Szczepaniec, 806-354-5806, ada.szczepaniec@ag.tamu.edu

AMARILLO – The potato industry may be losing a mainstay in the battle against psyllids, according to a recent Texas A&M AgriLife Research study.

Dr. Ada Szczepaniec discusses her greenhouse study on potato psyllid resistance to neonicotinoid insecticides. (Texas A&M AgriLife photo by Kay Ledbetter)

Dr. Ada Szczepaniec, AgriLife Research entomologist in Amarillo, said while there may be varying degrees of resistance to neonicotinoid insecticides in populations of psyllids across Texas, her recent study indicates they’ve lost their punch.

“We are able to provide strong evidence that these insecticides no longer suppress populations of psyllids below desirable levels,” Szczepaniec said. “However, there may be some biological control measures to help in this ongoing battle against the potato psyllid.”

The potato psyllid is a tiny insect with sucking, piercing mouthparts that transmits a bacterium, Candidatus Liberibacter solanacearum or Lso, which causes a disease called zebra chip and can cause tremendous losses to producers, she said. Producers have used the neonicotinoid insecticides to protect their solanaceous crops, mostly potatoes, in the past.

Szczepaniec said the study, funded by the Texas Department of Agriculture, indicates applications of neonicotinoid insecticides at planting, which are a considerable cost for producers, should be replaced with investments in post-emergence applications of insecticides other than neonicotinoids.

Integrating predators in suppression of psyllids could also be considered, especially when incidence of Lso is low and the threat of zebra chip disease is decreased, she said. However, more research is needed before recommendations regarding biological control can be made.

Her study included colonies of the potato psyllid from all major potato-producing areas of Texas. These colonies were established and maintained in the greenhouse for at least two generations before experiments examining their resistance to neonicotinoid insecticides began.

“Over the course of a year and a half, we completed testing the majority of the populations of psyllids for resistance to imidacloprid and thiamethoxam,” Szczepaniec said.

Colonies of the potato psyllid from all major potato-producing areas of Texas were studied. (Texas A&M AgriLife photo by Kay Ledbetter)

 

 

 

 

 

 

 

Based on the Insecticide Resistance Action Committee definition of resistance, “heritable change in the sensitivity of a pest population that is reflected in the repeated failure of a product to achieve expected level of control,” the potato psyllid populations across Texas are resistant to both neonicotinoid insecticides, she said.

Szczepaniec conducted a second study to identify alternative biological controls. Surveys of all arthropods associated with three different potato types – a russet, a red and a chipping variety – were carried out at the AgriLife Research station near Bushland.

“While we have only one year of data to draw our conclusions, the survey has revealed trends in predator abundance that have important implications for potato production,” she said.

“First, potatoes harbor a relatively diverse group of predators, and minute pirate bugs in particular are associated with potatoes throughout the season,” Szczepaniec said. “This is important because they were identified as key predators of the potato psyllid and their presence is important to suppression of the psyllid.”

She said other predators included long-legged flies, which are generalist predators, lady beetles, spiders, parasitoid wasps and syrphid flies. Russet potatoes had the highest prevalence of predators.

Second, Szczepaniec said, it was important that minute pirate bugs were strongly correlated with thrips, which were also abundant in potatoes throughout the season. Minute pirate bugs are highly attracted to thrips, which are not key pests of potatoes.

“So, it appears that the secondary pests, thrips, may help support a resident population of minute pirate bugs that can suppress the primary pest, potato psyllid,” she said.

However, Szczepaniec did not encounter significant numbers of potato psyllids in the survey, thus the impact of these predators on psyllids could not be established. It is likely, though, that if minute pirate bugs are present, it would inhibit colonization and suppress numbers of the potato psyllid.

“When the cumulative numbers of predators were examined over the sampling period, we noted relatively high initial numbers of lady beetles and minute pirate bugs that decreased in abundance immediately following a broad-spectrum insecticide that was applied to suppress grasshoppers,” she said. “This trend is not surprising and it validates our decision to survey potatoes in a field at our research farm that is not subject to an intense insecticide management program.”

Szczepaniec said while a transient influx of generalist predators can have an impact on pest suppression, the persistent presence of resident populations of generalist predators is key to effective biological control.

“We know managing the potato psyllid and zebra chip disease will require a comprehensive and integrated approach going forward, and this research successfully establishes one class of insecticides as no longer effective in potato protection,” she said.

“Given the high incidence of the key psyllid predator, we believe integrating insecticide applications at lower intensity than weekly sprays with biological control releases may provide a viable option for psyllid suppression, especially when the proportion of psyllids transmitting the pathogen is very low,” Szczepaniec said.

She admitted that much research remains to be done in order to test the feasibility of this approach. The next most immediate research focus will be to identify if populations of psyllids across Texas are resistant to any other frequently used insecticides.

 

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Farm & Ranch

                                                                          American Lotus

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By Tony Dean

Farmers and ranchers are in a very close partnership with Mother Nature. If we really pay attention, she presents us some interesting scenarios.

For example, though they are totally different types of plants, water lilies and prickly pear have a lot in common. They both have strikingly beautiful flowers, both plants are edible, both of them are invaders into their respective habitats, and too much of either one can be an obstacle that we have to deal with.

Many north Texas ranches rely on excavated ponds for livestock water. Any time a pond contains a significant amount of shallow water so that sunlight reaches the bottom, some type of pond weed will develop.  The plant family that includes water lilies and lotuses is a common invader in our livestock water.

Water lilies and lotuses are in the same plant family but they are two separate genera. There are easy ways to tell them apart:

  • A primary difference is that water lily leaves commonly float on the surface, but lotus leaves can grow above the water line.
  • Water lily leaves and flowers are thick and waxy, while lotus leaves and flowers are thin and papery.
  • Water lily leaves have a distinct notch in the leaf, while lotus leaves are more rounded.
  • Water lily flower petals are pointed, and lotus petals are more rounded.

The photos attached to this writing are from Clay County, and this plant is common across north Texas. American lotus is adapted to a wide area, from Honduras north through Mexico and across the eastern US and into Canada.

American lotus is a perennial, and it is cold tolerant and heat tolerant. It can grow in any pond or slow moving stream that contains shallow water areas.  It prefers water with a depth of about 12 inches. Germination can occur from the large lotus seeds. Tubers, or roots, are established in the mud, and long slender stems extend upward. Leaves and flowers are both emergent in that they grow above the water line.

Lotus flowers are fragrant, and yellowish white with rich gold centers.  They open in the morning and close by late afternoon, then open again the next day.

Lotus is an edible plant and has a history as a food source. The large tuberous roots, the size of a human arm, were baked like sweet potatoes. The leaves were eaten like spinach, and the large seeds were ground into flour. Stems taste somewhat like beets and were usually peeled before being eaten.

There is a large world-wide industry of cultivating lilies and lotuses in water gardens. According to        Dr. Jerry Parsons, Professor and Extension Horticulturist with Texas A&M AgriLife Extension, cultivation of these plants dates back as early as ancient Egypt. Today, anyone with determination and a little money can have a water garden.

In 2011, the 82nd Texas Legislature designated the water lily “Texas Dawn” as the official Texas State Water Lily. Texas Dawn is a hybrid developed by Texas resident Kenneth Landon, a world-renowned expert in the field of water lilies and the director of the International Water Lily collection in San Angelo.

Ducks and other wildlife utilize the large acorn like seeds of American lotus, and submerged portions of all aquatic plants provide some form of wetland habitat. Many of us have tried to pull a bass out of a group of water lilies or lotuses, and I’m sure others have had better luck than I did. Although there can certainly be benefits to lilies, lotuses, and other aquatic plants, they can also infest ponds to the extent that the pond is not functioning correctly.

So, while the rest of the world works hard to grow these plants, ranchers sometimes need to control populations in their stock ponds. Once it gets a foot hold, American lotus can spread aggressively in wetland areas.

The primary issue that encourages American lotus, and most other water weeds, is shallow water.  Look closely at a good livestock pond and you will find that the deeper water is basically free of infestation.  Any pond will have a certain amount of shallow water that encourages water weed growth, depending upon the terrain at the pond site and how the pond was constructed. Some ranchers who enjoy and utilize wetland habitat may prefer to have ponds with significant shallow water area.

Almost all livestock ponds have a certain life expectancy.  Siltation, or movement of soil into the pond bottom through rainfall runoff, is a natural occurrence.  How fast siltation occurs into each pond, and how deep the pond was to start with, determines the length of time that the pond will contain adequate depth for dependable water for livestock.

Ponds that develop infestations of water weeds over a large percent of the surface may not have adequate depth to remain a viable water source for livestock during drought periods, especially in  western north Texas where evaporation rates are higher.

Mud, or silt, from the pond bottom, can be removed to deepen the water, but this is a very expensive process.  It is often more economical to construct a new pond rather than try to remove the silt from an old one.  Most of us do not have the funds to continually construct deep water livestock ponds, so we must try to keep existing structures functioning and providing good drinking water for livestock, for as long as we can. Control of pond weeds like American lotus may be necessary, and it can be accomplished.

There is currently no feasible biological control. American lotus can be cut and removed, but this process us usually temporary because lotus can reestablish from seeds and roots.

American lotus can be safely controlled by chemicals. This must be done carefully.  If a pond containing a large amount of any pond weeds is treated to remove all of the vegetation, a fish die-off could occur.  When the dying weeds decompose, they use up the oxygen in the water and fish can suffocate. If possible, treat only a portion of the area, wait about two weeks, and treat another portion.

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Farm & Ranch

Tracks in the Sand

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This morning, I walked out into my arena and noticed something that gave me pause. The roping steers had been in there the day before, and even though the ground was wide and level, the sand carried their story. Hoofprints crossed every direction, but in several spots, the same trail was pressed deeper than the rest. Twelve steers had been turned out, yet more than a few chose the exact same path, wearing it down until it stood out from all the other tracks.

Cattle are creatures of habit. Anyone who has spent time around them knows this. They like routine: the same feed, the same water trough, the same shade tree in the pasture. When they are turned loose, they rarely wander without purpose. More often than not, they move together, following the same course as the steer in front of them. There are reasons for this: efficiency, safety, instinct. Walking a beaten path conserves energy, and following the herd is their natural defense. Even in an arena with no real destination, those instincts come through. By the end of a short turnout, you will see the evidence, lines where they have chosen the easiest way to travel and stuck with it.

Out on the range, those lines last longer. Before fences and highways, cattle drives cut deep paths across the land. The Chisholm Trail, which carried herds north from Texas through Oklahoma into Kansas, was walked by millions of cattle in the late 1800s. More than a century later, faint traces of those trails remain, worn so deep by hooves and wagon wheels that the land still carries the mark. On ranches today, you can see the same effect in pastures where cattle walk the same lines between water and grazing. From the ground those trails might look like nothing more than dusty ruts, but from the air, they sometimes stand out as sharp lines winding through otherwise open fields. Cattle do not simply pass over the land; they shape it. Every step adds up.

That simple truth extends beyond livestock. We all make tracks. Our habits and routines are our trails, worn in by repetition, sometimes efficient, sometimes limiting. Like the cow paths, they can serve a purpose, keeping us steady and helping us move forward. But when repeated without thought, they risk becoming ruts, keeping us from stepping into new ground. History offers perspective here too. The old cattle trails built towns and economies, but once railroads and fences changed the landscape, those paths were no longer useful. Sticking to them would have meant going in circles. Progress required something new.


The Tracks We Leave

Standing in the arena, I thought about the kind of tracks I leave behind. Most of mine are not visible in the dirt. They are pressed into my daily life, how I work, the way I handle challenges, the example I set. Some are helpful and worth keeping. Others may have outlived their purpose. The difference comes in knowing when to stay in the track and when to step out of it.

Tomorrow I will drag the arena and smooth it all clean again. The next time the steers are turned in, they will make the same trails. That is their nature. But unlike them, I have a choice. I can decide which paths are worth walking, which ones to change, and what kind of tracks I want to leave for others who might follow.

Tracks tell a story. Sometimes they are only temporary, fading with the next rain. Other times they last for generations, reminders of where herds and people once walked. This morning, the cattle showed me again that even the smallest things on the ranch carry meaning. Their tracks in the arena were not just marks in the sand. They were a lesson: every step matters, and the paths we choose shape more than just the ground beneath our feet.

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Farm & Ranch

Leopold’s Legacy: The Five Tools That Shaped Conservation

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By Raenne Santos

Known as the father of wildlife management, Aldo Leopold’s teachings reshaped our understanding of conservation and our role in nature. His philosophy, rooted in ethics, ecology, and action, emerged in response to the environmental degradation of the early 20th century in the American West. Overgrazed pastures, eroding soils, and changing wildlife populations revealed the consequences of treating natural resources as limitless. 

Recognizing these challenges, Leopold theorized a transformative approach to land stewardship, emphasizing that the land is not merely a commodity, but a community in which we all belong. His works, A Sand County Almanac and Land Ethic, are still referenced to this day by modern conservationists. In Land Ethic, he introduced a practical framework for wildlife management known as the Five Tools of Wildlife Management, which offers land stewards a structured approach to maintaining and restoring ecological balance.

Symbolizing brush management, the axe is one of Leopold’s tools for controlling invasive species, shaping habitats, and mitigating wildfire risks. By selectively removing vegetation, land managers can enhance biodiversity, create open spaces for native species, and maintain healthy ecosystems. 

Representing grazing animals, the cow (when used properly) mimics the natural disturbances once provided by bison. Grazing animals promote healthy ecosystems by aiding in nutrient cycling and soil disturbance. Responsible grazing practices prevent overuse and contribute to sustainable land management. 

The plow signifies mechanical disturbance and soil preparation, crucial for habitat restoration and agricultural productivity. Used strategically, it aids in cultivating crops and creating conditions favorable to wildlife. However, misuse can lead to erosion, requiring careful application in conservation efforts.

Fire, a powerful natural tool, plays a crucial role in maintaining biodiversity and landscape resilience. Land managers use prescribed fire to control invasive species, rejuvenate plant communities, and shape habitats. Fire promotes the natural cycles of ecosystems and supports species diversity. 

The final tool, the gun, is used to manage game populations and control predators. During Leopold’s time, unregulated hunting contributed to species extinction and posed threats to others. Today, hunting is strictly managed through game laws and seasonal regulations to ensure sustainable populations.

Leopold’s Five Tools of Wildlife Management continue to influence conservation practices today. While techniques have evolved, the fundamental principles remain the same—balancing human involvement with ecological processes to sustain healthy ecosystems. His approach emphasizes the importance of working with nature rather than against it. By embracing ethical land stewardship, modern conservationists honor Leopold’s vision, ensuring that future generations inherit thriving landscapes.

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