Invasive grain aphid makes first appearance in Colorado near Fruita
Special to the Free Press
Bob Hammon, an entomologist and extension agent from Colorado State University Tri-River Area Extension, found a colony of Sipha maydis along the edge of a wheat field outside of Fruita.
Similar to the Russian wheat aphid, this aphid feeds on cereal grains and grasses, such as wheat, resulting in yellowing and withering of the leaves which can reduce yields. This aphid can also transmit barley yellow dwarf virus, which is one of the most destructive diseases of small grain crops.
Hammon set out to look for the aphid just a few days after reading an article in “Entomology Today” about the discovery of a colony of them in New Mexico last fall.
He went out looking more to rule out the possibility they had made it to the area and his findings surprised him.
“I’m stunned that they’ve moved this far this quickly,” Hammon said.
He believes that by the amount of dead aphids found, some must have traveled to the area last fall.
New Mexico State University researcher and extension agent Tessa Grasswitz found the first colony of them in the middle of Albuquerque, N.M., last fall in a cover crop of oats on a small urban farm. She too had not expected to find them and had gone out in search of another aphid.
“That is one of the issues with these invasive species is that they catch everyone by surprise,” Grasswitz said.
The small colony she found is the only one that has turned up so far in New Mexico.
Favoring warm, dry areas, the aphid is widely spread across Europe, Asia, the Middle East and parts of Africa.
The aphid has also succeeded in spreading throughout Argentina in just four years: less than half the 10 years it took the Russian wheat aphid.
In Argentina, they refer to it as the “black aphid,” although it does not yet have a common name.
They have a distinctive shiny black color to them with small white spins visible under high magnification.
In North America, only a few encounters occurred before Grasswitz found the colony last fall. The first sighting occurred in 2007 in California, in Florida in 2011 and 2012 from produce that came from California, and lastly in a greenhouse in Georgia in 2012.
In these instances, the aphids were found on non-host plants, which meant they could not reproduce and start a colony, and therefore they posed no threat.
“There is a lot of land between [California and Georgia] so, if it’s here, it’s probably spread to some of those states in between,” Grasswitz said.
Small pests like aphids can spread in a number of ways. This aphid in particular has a broad range of hosts that it can survive on such as various grasses, oats, barley and wheat.
“I think it is part accidental transport in addition to its own powers of dispersal when it’s in wing form,” Grasswitz said of its rapid expansion.
Researchers believe that they can spread easily on non-host crops such as lettuce or other produce as well, which could explain how they ended up in California and then Florida.
So new to North America, researchers do not know much about the aphid or how to manage it at this point.
Hammon believes farmers can probably treat it like they would any other aphid with an early spring spraying, but the literature he has read suggests that the aphid prefers a more developed crop, which may mean a second treatment later in the season.
“With this mild winter, we are set up for a big infestation in year one,” Hammon said. “That’s exactly what happened with Russian wheat aphid. It was a mild winter and before we knew it, we weren’t even looking and it hit us. But, we have more warning this time, I think.”
The milder winter most of Colorado has experienced has the state up to experience a big pest year in general, Hammon said. Some native predators and parasites to this aphid do exist in the state, which may help keep the threat of them down, but only time will tell.
He suggests that farmers monitor their fields closely and scout for any yellow or discolored patches not only at the start of the season, but also as the flag leaf develops and in later stages of growth.
If a grower does believe they have the aphid in their fields, he said they should contact their local extension agent for identification and to discuss a treatment plan.
“We have to prepare for it because someone who doesn’t may get burned by it,” Hammon said. “But at least we know now to look for it.”
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