Winter survival of poorly developed wheat
* Is there any insect or disease damage to the plants?
Plants may die during the winter not from winterkill, but from the direct effects of a fall infestation of Hessian fly. Many people are familiar with the lodging that Hessian fly can cause to wheat in the spring, but fewer recognize the damage that can be caused by fall infestations of Hessian fly. Wheat infested in the fall often remains green until the winter when the infested tillers gradually die. Depending on the stage of wheat when the larvae begin their feeding, individual tillers or whole plants can die. If the infestation occurs before multiple tillers are well established then whole plants can die. If the plants have multiple tillers before the plants are infested then often only individual tillers that are infested by the fly larvae will die.
The key to being able to confirm that the Hessian fly is the cause of the dead tillers is to carefully inspect the dead plants or tillers for Hessian fly larvae or pupae. This can be done by carefully removing the plant from the soil and pulling back the leaf material to expose the base of the plant. By late winter all of the larvae should have pupated and thus the pupae should be easily detected as elongated brown structures pressed against the base of the plant. The pupae are fairly resilient and will remain at the base of the plant well into the spring.
Damage from winter grain mites, brown wheat mites, fall armyworm, aphids, and crown and root rot diseases can also weaken wheat plants and make them somewhat more susceptible to injury from cold weather stress or desiccation.
Symptoms of winter survival problems
If plants are killed outright by cold temperatures, they won’t green up next spring. If they are only damaged, it might take them a while to die. They will green up and then slowly go “backwards” and eventually die. There are enough nutrients in the crown to allow the plants to green up, but the winter injury causes vascular damage so that nutrients that are left cannot move, or root rot diseases move in and kill the plants. Slow death is probably the most common result of winter injury on wheat.
Direct cold injury is not the only source of winter injury. Under dry conditions, wheat plants may suffer from desiccation. This can kill or weaken plants, and is actually a more common problem than direct cold injury.