What symptom indicates the invasion of corn kernels by field fungi?

The indication of corn kernel invasion by field fungi is primarily reflected in the deterioration of kernel appearance before harvest. Fungi can cause various types of damage, leading to changes in the kernels' texture, color, and overall integrity. When fungi invade, they can produce mycotoxins that not only affect the quality of the corn but also its safety for consumption. Observing such deterioration suggests that the kernels have been compromised and may lead to decreased yields and lower market value.

In contrast, dark spots present only in storage would not necessarily indicate a pre-harvest fungal infection, as it may result from conditions occurring after the corn is harvested. Color changes in leaves relate more to plant health and viability rather than kernel integrity. Drying up of roots typically indicates issues related to root health or water availability, which do not directly correlate with kernel infection. Thus, the most accurate answer focuses directly on the visible symptoms of kernel quality, reinforcing the significance of monitoring for fungal invasive symptoms prior to harvest.