If you’re looking for good news, here's an encouraging word from Purdue University Extension Entomologists and plant pathologists. They believe that with one exception, corn flea beetle populations should begin the season at low levels. Since the beetle is that way Stewart's wilt is transmitted amongst corn plants, that should mean low levels of this disease as well.
Flea beetles and Stewarts' wilt haven’t been a big concern on commercial corn for the past four to five years. However, it can be more of an issue in years when flea beetle populations are high to seed corn and some specialty corn producers.
The only area of the state where Christian Krupke and John Obermeyer, Purdue university Extension entomologists, expect moderate levels of corn flea beetles early in the season is in extreme southern Indiana counties, dipping as far south as Mount Vernon in Posey County.
The reason populations of the beetle have remained low over the years since 2006, the entomologists say, is because of frigid temperatures during the winter. If the sum of the average daily temperature for the three winter months, December through February, is below 90, then the probability of corn flea beetle numbers is low.
The only disclaimer is that there was a fair amount of snow cover in some parts of the state during the cold weather. However, even with this factor built in, Krupke and Obermeyer still expect low numbers of flea beetles this spring, except in extreme southern Indiana.
You may still want to sample highly-susceptible corn fields, especially areas near grass borders or waterways. If you’re growing a susceptible crop and find beetles, you may want to consider treatment. Usually low rates of Poncho or Cruiser provide protection through the two -leaf stage, with high rates providing protection through the five-leaf stage.
Should a situation develop where you need to spray after corn is up, consult labels carefully. Some labels restrict spraying for this insect along field edges and near waterways because the insecticide could potentially move into a creek or stream.
Kiersten Wise, Extension plant pathologist, says Stewart’s wilt, when it does occur, can be in either a seedling wilt or leaf blight form. In the wilt phase, plants wilt rapidly while small. Sweet corn hybrids, some dent corn inbreds in seed production fields and even some dent hybrids and popcorn lines can be susceptible.
The leaf blight phase typically is apparent at tasseling, and may be confused with gray leaf spot, northern corn leaf blight, or Goss's wilt.
It’s good to be vigilant. The best news is this is one pest and life cycle-tied diseases which may be less of a problem this year than in some other seasons in the past in Indiana.