Fun fact: Potatoes are the top vegetable crop in the U.S. According to USDA-NASS, one million acres of potatoes were harvested in 2020, with a total value of $3.88 billion. That’s why protecting them is a valuable investment.
Luisa Parrado, Emilie Cole and Marisol Quintanilla of the Department of Entomology at Michigan State University shared a poster presentation at Great Lakes Expo based on their research using manure-based amendments on potatoes and how two pests in particular fared within those amendments.
The team was looking specifically at potato early die, a disease complex caused by the interaction between the root-lesion nematode Pratylenchus penetrans and the Ascomycota fungus Verticillium dahliae.
They noted, “This disease complex can reduce potato yields up to 50%. Both pathogens have a wide host range, including weeds that are common in potato fields.” Some characteristic symptoms of potato early die are the yellowing of lower leaves, chlorosis, stunting and vascular discoloration in stems and tubers.
The goal of their study was to investigate the response of P. penetrans and V. dahliae to different manure-based amendments with different carbon-to-nitrogen (C:N) ratios under normal field conditions. Eight different treatments were evaluated on a commercial potato farm in southwest Michigan. There were five manure-based amendments featuring different manure sources (either poultry or cattle) and varying C:N ratios (5:1 up to 21:1) – these were cattle manure compost, cattle manure compost plus gypsum, poultry manure, poultry manure compost and pine bark and cattle manure compost.
There were two positive controls that used Vydate®L (insecticide and nematicide) and CruiserMaxx® (insecticide and fungicide). There was also an untreated control plot. The potato variety being grown was Russet Norkotah, an early to medium maturing variety that’s normally very susceptible to blights and often to early dying, according to the University of Nebraska’s Institute of Agricultural and Natural Resources.
The researchers measured the population of P. penetrans in the soil before treatment, 45 days after treatment (DAT) of amendments and again at harvest. They also looked at P. penetrans incidence in the plants’ roots 45 DAT and 75 DAT. They measured V. dahliae in plant stems at 45 DAT and 75 DAT. The team also performed tuber inspection for internal defects, including vascular discoloration. Overall crop productivity was considered as well.
What were the results? The good news is that the applications of Vydate L and poultry compost (with a C:N of 13:1) reduced P. penetrans in the soil up to 75% and 45%, respectively. The bad news is that cattle manure compost plus gypsum actually showed an increase of the nematodes of 24%.
Other notable results were that applications of poultry manure (with a C:N of 5:1) prevented P. penetrans from highly reproducing within roots. “With poultry manure there was only a 25% increase of P. penetrans, while in the untreated plot there was an 89% increase,” the team stated.
Applications of the compost blend (with a C:N of 8:1) resulted in the lowest proportion of tubers with vascular discoloration (12%) in comparison to the control (which saw more than 25% with discoloration).
Finally, the researchers reported that there were no significant differences found on tuber yield with any of the treatments; however, applications of manure-based amendments did increase yields in comparison to the untreated control plots and those with Vydate L. It seems like poultry manure and manure compost may be viable options for at least some control of potato early die.
by Courtney Llewellyn