Agricultural Research Division of IANR



Kent M. Eskridge

Date of this Version



Plant Dis. 98:1248-1252.


© 2014 The American Phytopathological Society


Aphanomyces cochlioides and Rhizoctonia solani are important soilborne

pathogens causing root diseases that are primary constraints to

sugar beet production in Nebraska, Colorado, and Wyoming. These

types of diseases are difficult to control because they are often not

noticed until substantial damage has already occurred. Efforts to manage

them would be more effective if techniques were available that

were more predictive than reactive. Therefore, a preplant soil test was

developed to estimate the relative pathogen populations in the soil and

to predict potential root disease problems later in the growing season.

Preplant soil samples collected from fields to be sown with sugar beet

were planted with a susceptible cultivar and tests were conducted for 1

month in the greenhouse. A preplant disease index was developed

based on the time period during the test that seedlings became infected

and was calculated on a 0-to-100 scale. Disease index values were

compared with yields obtained from the same fields after harvest.

Analysis of data collected for 5 years (2003 to 2007) with analysis of

covariance revealed a strong relationship between the preplant disease

index values and recoverable sucrose and root yields but not sucrose

concentration. Results indicated that, for each unit increase in the

preplant disease index, root yield decreased by 0.27 metric tons (270

kg) per hectare (P < 0.05, R2 = 0.44) and recoverable sucrose decreased

by 49 kg/ha (P < 0.05, R2 = 0.45). We concluded that this

preplant soil test can accurately predict root disease potential due to R.

solani and A. cochlioides, and has the potential to help producers make

effective management decisions in production fields using the index

procedure. This soil assay has additionally provided new information

on the biology, incidence, and distribution of root pathogens in production

fields throughout the Central High Plains.