U of I Monitoring Program: Few Potato Psyllids But Slightly More Infected
A University of Idaho (U of I) pest monitoring program caught very few potato psyllids in Idaho potato fields for the second year in a row in 2023; nevertheless, a small percentage of psyllids harboring the bacteria that causes zebra chip disease in crops were somewhat greater than usual.
“Zebra chip was observed to some extent in the field, but I have not heard of any major disasters,” U of I entomologist Erik Wenninger, who oversees the potato psyllid monitoring program, mentioned.
Small, flying insects called potato psyllids are capable of spreading the Liberibacter bacteria that causes zebra chip in potatoes. The disease not only lowers yields and affects plant health, but it also causes darkening of the bands across the tuber meat when fried, making the contaminated potatoes unsaleable.
U of I’s new central center for university pest monitoring initiatives, idahopestmonitoring.org, provides average psyllid numbers and positive tests for Liberibacter by area during the growth season. The website furthermore presents findings from a network of fungal spore trapping as well as data from aphid monitoring in northern and southern Idaho.
Compared to about 1% in most years, almost 6% of all psyllids caught throughout the season tested positive for the bacteria. Even though 2023 had a higher number of psyllid captures than 2022, 22% of psyllids taken in 2022 tested positive.
Zebra chip first surfaced in the Pacific Northwest in 2011. During the following growing season, UI Extension, working with an ad hoc group of industry officials and other stakeholders, launched a comprehensive annual monitoring program. The program entails placing yellow sticky traps in potato fields throughout the state and testing any captured psyllids for the presence of the bacterium to alert growers. U of I works with crop consultants and processors who collaborate with their growers to have sticky traps set on the borders of 70 to 100 fields.
Psyllids arrived in large numbers in 2012, and 28% of them tested positive for Liberibacter. Disease pressure has been much lower since 2012, and the stakeholder group chose to scale back its monitoring program beginning in 2018. For example, the duration of psyllid trapping and testing has been shortened by several weeks, and the number of sticky traps they set out has been reduced.
The Idaho Potato Commission covers the roughly $30,000 cost of potato psyllid monitoring and testing, and potato growers receive a good return on their investment.
“I think given the potential for disasters, which we did see in other years and other growing areas have seen, the relatively small cost of the monitoring program is worth it. A lot of growers use our monitoring program to make insecticidal decisions. The biggest benefit is if they don’t see psyllids and bacterium, they can hold off on insecticides. Without the information they may tend to spray just in case,” Wenninger concluded.
