Hail Damage Impacts on Corn Productivity: A Review

Hail influence on corn (Zea mays L.) yield depends on defoliation timing and severity. Complete defoliation during early vegetative stages can have minimum yield effects if plants’ growing point is not affected but can generate some delays in the planting to flowering period. Low-severity defoliations after V10 can reduce yield up to 30%. Higher severities gradually increase yield penalties to a peak around flowering and decrease progressively during the grain-filling period. Charts to estimate the percentage of corn yield loss due to defoliation developed in the late 1960s are still accurate in most situations but fail to describe particular situations. Defoliation around VT commonly affects time to silking, anthesis–silking interval, and plant growth rate, but not time to anthesis, and is commonly explained by lower kernel number (KN). Defoliation at R2 commonly affects kernel weight (KW), without changing KN. However, several studies showed a reduction in both KW and KN with R2 defoliations. Under low plant disease pressure, fungicides applied around VT do not help reduce any yield defoliation impact. Specific genotypes, row spacing, and hybrid maturity can influence crop yield defoliation responses. More studies are warranted to confirm the potential for narrow rows to reduce yield loss after defoliation.