Sugarbeet growers in southern Idaho and eastern Oregon don't like beet leafhoppers. And it's not because the tiny insects prefer sugarbeet plant stems as their food of choice-it is because during their sugarbeet foliage feasts, beet leafhoppers can infect plants with curly top virus, a devastating disease transmitted to the plant by this insect.
While leafhoppers and curly top virus are not new to sugarbeet growers in the Pacific Northwest-area reports about the pests date back to the early 1900s-they remain a threat to sugarbeet crop production every year. Advancements in genetic and pesticide technology now allow growers to better protect themselves from the beet leafhopper, and ultimately, curly top virus. By properly identifying, preparing for outbreaks and monitoring fields, sugarbeet growers can keep leafhoppers and curly top at bay to better realize yield potential.
Beet leafhoppers and curly top virus exist in a symbiotic relationship in which the virus depends on the insect to travel and infect crops. While virus-free leafhoppers cause damage to sugarbeets, they shouldn't be a target pest for growers.
"Beet leafhoppers will feed on plants similarly to aphids or cicadas by using piercing/sucking mouth parts to obtain sap from the plants," said Erik Wenninger, entomologist at the University of Idaho. "It would take a lot of leafhoppers on a sugarbeet plant for a grower to be concerned about them killing the plant by sucking its sap. The real concern is their transmission of curly top virus, which can cause growth stunting and even kill the crop."
The leafhopper, which is about an eighth of an inch long, wedge-shaped and pale green, gray or brown, serves as the only insect vector by which curly top viruses can travel and infect fields. Once infected with a strain of the curly top virus, sugarbeet plants will have smaller, crinkled leaves that curl upward and inward. Plant veins will also become more apparent, swollen rootlets become shaped irregularly and root and beet growth is stunted. A new rootlet system will then grow, resembling the hairy appearance associated with Rhizomania, although the diseases are unrelated.
"Sugarbeets infected with curly top virus will show stunted growth and will certainly have reduced yield," Wenninger said. "If there is enough disease pressure, curly top virus can actually kill sugarbeet plants."
Wenninger said growers should regularly monitor their fields and apply crop protection products appropriately to help prevent curly top and contain plants already affected. Containing the disease can help prevent the virus from infecting other fields and will help salvage what's left of an infected crop.
It's difficult to predict annual pressures from leafhopper and curly top until seasonal conditions begin to unfold as winter ends. Warmer temperatures allow growers to plant sugarbeets early, but can also indicate leafhopper behavior for the upcoming season.
"Depending on how hot and dry the spring is, weather can heavily influence what kind of curly top year we have," Wenninger said. "If it's a relatively cool and wet spring, then the host plants in the desert are going to have enough moisture to stay alive longer, and beet leafhoppers will remain there. Once it gets hot and dry, winter hosts start dying, and leafhoppers move to other hosts such as sugarbeets."
The Pacific Northwest has seen relatively cool spring weather the past few years-cool enough to keep leafhopper and curly top pressures low. While these recent trends have been favorable for growers, experts warn that there really is no indication for how heavy leafhopper and curly top pressures will be this growing season.
Sugarbeets are naturally prepared for curly top without assistance from genetic engineering or pesticides.
However, this naturally occurring resistance becomes stronger as the beet grows, which means young plants are more vulnerable to the disease and insect.
"Sugarbeets have natural age-based resistance to curly top. All varieties will exhibit some type of resistance. When plants are young, they are more susceptible; the older the plant is, the more resistance is expressed," Wenninger said.
While sugarbeet's natural tolerance to curly top is beneficial, the plants aren't able to fend off heavy infestations alone. Ensuring protection from beet leafhopper and curly top can be achieved with resistant seed varieties and application of the proper crop protection products.
"Using resistant-bred varieties is the first and best line of defense for growers," Wenninger said. "There are several insecticides that can be used as a supplement to curly top resistant varieties. Soil- or seed-applied insecticide treatments tend to be more effective because they can be systemic, which means the product will actually move through the plant tissue, as opposed to a contact pesticide that stays on the foliage of the plant."
To help sugarbeet growers keep their crops pest-free and realize full yield potential, Syngenta offers Hilleshög brand varieties and CruiserMaxx Sugarbeets insecticide/fungicide seed treatment, a combination of separately registered products, for systemic protection of leafhopper. Drawn from a genetic portfolio spanning more than 100 years, Hilleshög brand high-quality seeds deliver unmatched curly top resistance to keep sugarbeet plants healthy and strong.
"Hilleshög seed is a leader in genetic tolerance for curly top resistance, and CruiserMaxx Sugarbeets helps further protect crops from curly top," said Doug Ruppal, sugarbeet crop specialist at Syngenta.
"CruiserMaxx controls beet leafhopper in the critical early-life stage of the plant. As sugarbeets emerge they begin to systemically take up the insecticide from CruiserMaxx Sugarbeets, which will control beet leafhoppers in young plants."
from the start
While beet leafhopper and the curly top virus have always been a problem for Pacific Northwest sugarbeet growers, advancements in research and breeding technology have made the crop profitable despite the century-long battle growers have had with the pests.
"Curly top nearly ruined the sugarbeet industry in the Pacific Northwest in the early days of cultivation," Wenninger said. "It wasn't until varieties resistant to curly top were developed that growers really got a handle on it."
And given all the modern technology and crop protection, Ruppal recommends preparing for, rather than reacting to, beet leafhopper and curly top infestations from the start each year.
"Once curly top starts infecting the plant, it's too late for growers," he said. "It is always a good idea to have sugarbeet plants protected from the beginning. You just never know when beet leafhoppers and curly top are going to enter a field."
For more information on Hilleshög brand sugarbeet seed and CruiserMaxx Sugarbeets seed treatment, contact your area Syngenta representative.