Issue No. 19, Article 5/July 31, 2009
Hail Damage in Northern Illinois
Jim Morrison, extension educator in crop systems located at the Rockford Extension Center, indicated that strong storms in northern Illinois on Friday, July 24, produced large hail and damaged corn and soybean crops in its path. Jo Daviess and Stephenson counties were hit particularly hard; one producer said hail was 1.5 inches in diameter. Windows and siding on homes were damaged in addition to crops. Hail damage occurs in isolated areas just about every year; as a general rule, the later in the season hail falls, the more severe the yield penalty.
In quick review, the first reproductive stage (R1) begins with the first flower formed on the main stem. Successively, a flower on one of the two uppermost nodes with a fully developed leaf is R2, a 5-mm pod on one of the four uppermost nodes with a fully developed leaf is R3, a 20-mm pod on one of the four uppermost nodes with a fully developed leaf is R4, and a 3-mm seed in a pod on one of the four uppermost nodes is R5. A green seed that fills the pod cavity on one of the four uppermost nodes is R6, one pod on the main stem that has reached its mature pod color signifies beginning maturity (R7), and nearly all pods reaching mature pod color signifies maturity (R8). Not all plants will be at the same maturity level at the same time, so the percentages of plants at different levels are used to indicate the maturity at the "field level." For example, if 50% of plants are R6 and 50% are R7, the field is R6.5.
It is critical to assess yield losses field by field because several factors are at play. The biggest factors are the amount of leaf defoliation, soybean growth stage, and--the most difficult to assess--stem and pod damage. Soybeans are most vulnerable to hail damage that occurs between R5 and R6.5.
A northern Illinois soybean field in the R2 growth stage following a hailstorm on July 24, 2009. (Photo courtesy of Jim Morrison.)
A northern Illinois soybean field between the R3 and R4 growth stages following a hailstorm on July 24, 2009. (Photo courtesy of Jim Morrison.)
At R2, 90% leaf defoliation can occur and 80% of the expected yield can still be produced. Yield can be reduced to two-thirds and one-third of the expected level if 90% defoliation occurs at R4 or R6, respectively. In general, yield losses are usually less severe than the producer fears right after the storm; again, yield loss estimates need to be done on individual fields. If you find yourself in this situation, contact a trained crop adjuster and give the crop several days to recover before making any rash management decisions you hope will improve the situation.--Vince M. Davis