Hot and dry conditions may have some benefits for Panhandle crops, as long as they are irrigated. In general, yields for both dry edible beans and sugarbeets were very good in 2021, says Nebraska Extension plant pathologist Bob Harveson, who is based at the Panhandle Research and Extension Center in Scottsbluff.

“For beets and dry beans, I have heard of no major problems in Nebraska,” he says. “I can speak only about the results we got from our own research plots. Last season was characterized by extremely hot conditions with little to no additional rainfall in most of the region. I know our plots received no moisture beyond irrigation.”

It was tough to keep the plots wet enough because of high temperatures, but Harveson reports excellent yields overall.

Projected production

In October, USDA’s National Agricultural Statistics Service reported a forecasted yield for 2021 of 2,580 pounds per acre on dry edible beans, up 310 pounds per acre from 2020, with a total projected production at that time of 2.79 million cwt.

That said, the harvested acreage in Nebraska was down by 32% from the previous year, at 108,000 acres, so the projected overall production was down by 23%.

Sugarbeet production was forecast in the same report at 1.3 million tons for Nebraska, down 9% from 2020. USDA said that the harvested area for beets was 43,600 acres, down 5% from the previous year. Yield estimates at the time were at 29.7 tons per acre, or 1.3 tons per acre less than 2020.

Disease factor

“We had very low levels of diseases like Cercospora leaf spot, which is good for the growers but bad for researchers to properly evaluate various treatments tested for disease control,” Harveson says. “This was surprising to me. The same relationship could be told for Asochyta blight with chickpeas, and bacterial diseases in dry beans — it was simply too hot and dry for high levels of disease.”

Projecting disease pressure into 2022 is difficult, because no one knows exactly how the weather patterns will play out. “In some instances, when the winter is mild, there is a surge in diseases caused by bacterial pathogens [common blight or bacterial wilt] later during the growing season because they have had better conditions to survive on crops residues remaining on the soil surface,” Harveson notes.

Although it would not be useful for foliar diseases on sugarbeets, there is a disease index that can help with root pathogen management. “The disease index is a pre-plant soil test that was developed and utilized by the plant pathology program at the UNL Panhandle REC,” Harveson says. “This test is conducted in the greenhouse and designed to test soils that will be planted to sugarbeets the following spring.”

ROOT DISEASE INDEX: This photo illustrates the growth differences of two fungal pathogens and how they are identified from the disease index. Characteristic hyphal growth is seen in the culture of Aphanymyces cochliodes (right) and Rhizoctonia solani (left) emerging from infected seedlings planted at the same time in the plant pathology lab.

Since several common soilborne sugarbeet root pathogens can cause both seedling and root rot disease, the primary purpose of the test is to identify and estimate relative populations in the soil and then predict the potential for root disease problems caused by these same pathogens later in the season.

“We can monitor for Fusarium, Aphanomyces and Pythium. However, the test is particularly useful for estimating risk of disease problems caused by Rhizoctonia,” Harveson says. “We began this concept as a service for the growers in 2003, and as of December 2021 have analyzed well over 4,000 [4,266] soil samples, each representing one sugarbeet field.” 

Methodology

According to Harveson, the soil samples should be taken from the upper 4-6 inches of depth from multiple locations within a field and combined into one sample. This gives a better representation of the entire field, like samples taken for fertility analysis.

The collected samples are brought to the Panhandle REC plant pathology diagnostic lab, mixed thoroughly, planted with a susceptible cultivar and maintained for four weeks. Seedlings are observed daily, and pathogens are identified as symptoms appear and seedlings begin to die.

An index was developed based on the time period during the 30-day test that seedlings became infected and was calculated on a 0-100 scale.

“We have also empirically designed a risk assessment system [high, medium and low] for each tested field based on the disease index values obtained from the soil assay,” Harveson says. “We consider an index value of 30-45 to represent a moderate risk of disease problems from these pathogens later in the season. Anything above 45 would represent a high risk, while any values below 30 would be considered a low risk.”

To validate the concept, pre-plant index values from 108 fields over a five-year period were compared with yields obtained from those same fields after harvest. Results revealed a strong inverse relationship between the pre-plant disease index values and sucrose and root yields, but not sucrose percentage.

Harveson adds that this means the fields with higher disease index values also resulted in lower root yields and total sugar per acre. For instance, after further analysis with linear regression of the data, the test showed that for each single numerical unit increase in the disease index, a corresponding decrease of 0.12 tons (240 pounds) per acre and 44 pounds sucrose per acre, respectively, was revealed.

“The take-home message for this work is that we feel that the disease index can accurately predict root disease potential, particularly Rhizoctonia root and crown rot,” he says. “Another example of the benefit for this test to consider is low-risk fields. Based on test results, no action would be recommended for low-risk fields, thereby saving the cost of any unnecessary treatment.”

More importantly, studies suggest that the information obtained from the tests will assist growers with making management decisions based on the disease index predictions. “Therefore, we will continue this service for as long as there is an interest in using it,” Harveson adds.

The cost for this service is $35 per sample. For any questions, contact research technicians Allison Rickey or Tyler Patrick at 308-632-1230, or Harveson at 308-631-5953 or email [email protected].

Panhandle REC news release contributed to this article.