- Entire plants may be pulled from the ground, especially in loose or moist soils.
- The plant characteristics at the point of damage will usually have a rough appearance since deer lack upper incisors.
- Deer may browse leaves of corn, but often damage is a complete bite of the stalk below the tassel and at the center of the growth whorl.
- Damage to ears early during their development will result in a telescoping husk as they mature.
- During the silk stage, deer bite the tender, succulent corn silks.
- Deer often remove kernels by using their lower incisors to scrape an ear along its length.
- Deer occasionally completely pull the ear from the plant.
- Deer can knock down stalks of corn. Signs of deer damage include a small number of stalks knocked down, and all lying in the same direction.
- Most raccoon damage to corn is concentrated during the milk stage of development (R3), but some damage also occurs before and after the milk stage on into maturity.
- Some raccoon damage is characterized by downed stalks along a 2- to 3-row band.
- Depending on the size of individual raccoons and the height of the ear above ground level, raccoons will either stand on their hind legs and feed on the lower hanging ears on the stalk, or climb the stalk to reach the ear. In either case, the corn stalk will usually break.
- This method of feeding by raccoons results in a haphazard array of broken corn stalks lying in different directions. Some may describe this pattern as a very chaotic picture.
- Raccoons do not bite through the husk, but rather pull the husks open with their teeth and claws to expose the kernels. Husks will have a shredded appearance and cobs will appear masticated with many torn seed coats remaining on the cob.
- Corn cobs fed upon by raccoons on the ground often will have a muddied appearance.
- Upon close inspection, raccoon tracks may be visible on the leaves and husks – a result of mud or the milky corn residue covering their paws.
- Claw marks also may be visible on the stalk, leaves and ears.
Damage caused by squirrels is concentrated at both the early- and late-developmental growth stages of plants. Unlike birds, squirrels and other mammals have a keen sense of smell.
- Damage by squirrels is almost entirely limited to field edges adjacent to quality squirrel habitat.
- Squirrels dig up seed prior to emergence or pull seedlings shortly after emergence.
- Squirrels feed only on the remaining seed and leave the rest of the plant.
- Generally, when squirrel damage occurs the soil will be dug to one side.
- Significant reduction in stand densities occur along the field edge where damage has taken place.
- Chipmunk and most other small mammals are too small to excavate a large hole all at once. Consequently, they will dig around a plant to expose the remaining attached seed.
- From the milk stage through maturity, squirrels and smaller rodents will feed on kernels from intact ears. Parts of kernels often are visible scattered on the leaves and ground below individual plants. Small mammals will most often consume only the hearts of the corn kernels.
The beaver is the largest rodent in North America. Like all rodents, they have sharp incisors and bite cleanly through plant stems and twigs. Beaver are nocturnal and cause damage at night in fields relatively close to open water. Many people are familiar with the lodges beaver construct within ponds, but beaver also excavate bank dens along rivers and streams.
- Time of damage to corn is limited to late vegetative stages of growth just prior to the tassel stage, and lasts until before browning/maturity of the stalk. Damage to corn caused by beaver is easily identified. Stalks are cleanly cut close to ground level at about a 45-degree angle.
- Beaver will usually drag the cut stalks along a conspicuous path, or “beaver run,” towards the water.
- Some cut stalks may be visible along the water’s edge.
Blackbirds and grackles will damage corn early in the vegetative stages of development as well as during the reproductive stages. Bird damage to corn can occur throughout a corn field, and is not necessarily concentrated along the edges. Birds have a poor sense of smell and cannot easily find buried seeds; thus, bird damage to recently emerged corn may be confused with that caused by squirrels and vice versa.
- Birds will dig around a seedling with their bill. The damage will look very similar to digging by chipmunk and mice. However, with bird damage, entire seedlings may be pulled from the ground and the resulting hole will generally be shallower than those dug by mammals.
- During drier conditions and in fields with soils of high clay content, seedlings often are broken off by birds.
- During the reproductive stages of corn development, blackbirds peel the husks from the tip of the ear back towards the base in very thin strips.
- During the milk and blister stages, birds peck out the kernels and leave a cup-shaped shell.