Farm Progress

Harvest is a critical time when disease-causing organisms and nematodes can be spread within fields and across fields. Given the urgency of harvest, controlling this spread can be challenging.

Bob Kemerait, Plant Pathologist

November 12, 2018

4 Min Read

In the devastation some endured in the aftermath of Hurricane Michael, harvest continued as best it could. 

The urgency before the storm, when growers struggled to keep pickers and combines ahead of the wind and rain, gave way to what was left. In a time like was experienced, the last things on a farmer’s mind would be diseases and nematodes. But if I could capture a grower’s attention, even briefly, I would encourage him to consider two things:

No. 1 — During harvest growers have an opportunity to observe and assess damage from diseases and nematodes that have been hidden earlier. Damage to roots, pods, bolls and lower limbs may be unknown until harvest. Other damage, such as premature cutout, stunting and even plant death may be most obvious when harvest is under way. Taking time to get the problem diagnosed, either through collection of soil samples or with the help of Extension agents and consultants, can be key to management decisions for 2019.

No. 2 — Take the time and effort needed to avoid spreading plant-parasitic nematodes and disease-causing organisms from infested fields to fields where the problem has yet to occur. Field sanitation and care in moving equipment between fields may not be convenient, but such practices can be crucial in the battle to keep risk to diseases and nematodes low from field to field.

“Excluding” diseases or nematodes from a non-infested field is a critical management strategy and simply means “keeping the bad stuff out.”

As a small boy in Florida I knew about hurricanes, but I didn’t know about nematodes, or that plants got sick.

During the mosquito-infested summer months, my grandmother and my mother went to great lengths to teach me about “exclusion” even if I didn’t know the word. “Exclusion” meant screens on the windows and screens on the doors. Screens were to keep mosquitos out and to let some breath of air in.

Screen doors were to be kept closed and my propensity to push pencils, or anything else, through the window screen was met with sharp rebuke and punishments sufficient to insure a boy would never do that again. 

Failures in our efforts to exclude mosquitoes became fully evident at night. The door left open or the ripped screen seemed innocent enough in daylight hours, but at night the incessant whine of mosquitoes in my ears was my punishment.

As young children, two of my sisters and I shared a room and we would follow the same routine nightly before sleeping. We scanned the room carefully, excitedly pointing out to our hapless mother the mosquitos collecting on the ceiling and the walls. It was her job to crush them, which she did with great skill. Nonetheless, she could never kill them all and the whine of even a few hungry bloodsuckers was enough to give us a long and restless night. 

Some soilborne diseases affecting our row crops are widespread, others are much less so and keeping them out of a field should be a priority.

White mold (stem rot) on peanuts is present in most, if not all, of our peanut fields and it is too late to try and keep it out. The severity of this disease can be reduced by use of resistant varieties, crop rotation and fungicides. 

Other diseases, like Cylindrocladium black rot (CBR), are not present in most fields and “excluding” them should be a priority. 

Movement of infested crop debris and soil, possibly through erosion, tillage, movement of “dirty” equipment can explain both expanding zones of affected plants in a field and spread of nematodes and diseases like CBR of peanuts and soybeans and Fusarium wilt of cotton from one field to another. 

The presence of these nematodes and diseases is likely not detected immediately, but over time the damage to a crop can be extensive and management strategies difficult.  Like the mosquitoes of my boyhood, efforts to keep these problems out are much more effective than trying to manage the problem when it is established.

Harvest is a critical time when disease-causing organisms and nematodes can be spread within fields and across fields.  Given the urgency of harvest, controlling this spread can be challenging. However, an awareness of how spread can happen allows growers to make some effort to minimize the problem. 

While it is impossible to stop the scatter of debris and even dust when pulling a peanut picker through a field, efforts to clean debris from combines and pickers and soil from tires of vehicles passing from field to field are effective measures limit spread to other areas. 

Because of the movement of equipment over many fields and considerable distances, it is obvious how problems can travel with them in infested debris and soil.

Harvest is a busy time, made even more difficult in the aftermath of the storm. However, with a little effort now to detect and diagnose diseases and nematodes in a field and to minimize their spread, growers will have an easier time in seasons to come. 

God Bless those who have lost so much.

About the Author(s)

Bob Kemerait

Plant Pathologist, University of Georgia

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