Some rain began to fall in dry areas this week which was much needed, but unfortunately, it brought hail, lodging and some flooding in areas of north and east Georgia. This is certainly the time of year we can expect reasonable rainfall to occur throughout Georgia but the last couple of events have been more severe than usual. Every year we experience some type of hail damage, flooding, and lodging in our corn crop, but this was a little earlier than normal. The question is how much damage is enough to cause yield loss. Damage from hail, flooding and lodging is highly dependent on severity and plant age. There is no standard for assessing damage very quickly in flooding or lodging, but there is for hail damage (more on this at the end of this blog).
Corn can be quite resilient if the weather damage occurs at specific growth stages. The keys in assessing the damage to corn are primarily time and knowing the plant age. Lodging in corn that is young such as a V7 or V8 (or younger) is seldom a problem as it can quickly recover even if it appears flat on the ground. Older corn may lodge at the V12-V14 stage if winds are very high and soils wet but often, it will recover unless the roots are exposed. In most cases, if roots are exposed before ear set, the crop will “goose neck” upwards. Some yield loss can occur under these circumstances but the crop remains harvest-able. In looking at corn for 35+ years, I’ve seen corn flatten a few times after ear set. IF it occurs early in silking, damage is usually severe but if it occurs late in dry down, it is harvest-able (albeit very slowly). All of this is different than green snap. High winds can cause green snap in corn. This damage is easy to assess simply by determining the percentage of affected plants.
Corn can handle flooding depending on the extent and age of the crop. Young corn can survive flooded conditions lasting for about two days under warm temperatures (~ mid-70s+,) to four days under cooler temperatures (at or below the mid-60s). How much of the plant was submerged and how quickly the water recedes influences it’s survival. Corn plants that survived flooded conditions will show new leaf development within three to five days after water recedes. Flooded or saturated conditions will restrict root development, reducing the crop’s ability to take up water and nutrients and tolerate drought stress later. If the crop is past silking and floods above the ears, it will suffer a total loss.
Fortunately for those suffering hail damage, there is a very good publication which has become the national standard of hail damage assessment in corn and was published in the National Corn Handbook. The following is the url for the publication: http://corn.agronomy.wisc.edu/management/pdfs/nch01.pdf . If you believe you have enough damage, make sure to call your insurance agent. I do encourage growers to wait at least 4 to 5 days at a minimum before making any decisions or judgements calls.
To assess the impact of the hail damage, first determine the amount of defoliation that occurred. Then carefully determine the growth stage. Now let’s say you determined your corn is at the 10th leaf stage and you estimate about 50% tissue damage. Look at table 3 provided in the publication, go down the first column to leaf 10 stage and move across the top of the table to 50 percent leaf area destroyed. Go down to the row = 10 leaf and you will see that it is estimated to lose 6 % of its yield. If the plant is older and you do not see the tassel in the whorl, then count the leaves and add at least five if you know the plant is over 4 to 5 feet tall. Find the assessed age in the chart to determine damage. As I said, corn is fairly resilient. However, we must still manage the crop. It is important to continue to irrigate and protect the crop from diseases by spraying fungicides and insecticides as needed. Corn can be quite ugly under light to moderate damage and the damage LOOK severe but, in my experience, it is a “food making machine” and will still produce a very profitable yield. If you need help assessing the damage, give your county extension agent or consultant a call to walk through it with you. It can be stressful, yes, but over the years, I have found the information in the table to be very good.