EXAMINING THE EFFECTIVENESS OF FUMIGANT APPLICATION ON SWEETPOTATO CROP

(TriCal Sweetpotato Trial (Livingston, CA): Harvest)

The demand for sweetpotatoes across the United States has increased dramatically for the last several years, reaching its apex in 2015 with record high production of 3.1 billion pounds. In 2021, the average American consumed about 6.3 pounds of sweetpotatoes. Why such increased popularity for this particular crop? Sweet potato fries account for the upswing in demand due to their higher nutritional content than traditional fries. For farmers to meet this demand, fumigation of the soil can greatly increase their yield and control pests like nematodes.

A recent study was held in Livingston, California by Dr. Kristi Sanchez and PCA Ole Fernandez and Jaime Garcia to determine the effectiveness of Telone and Chloropicrin on sweet potato plants in order to control nematode infestation. The issues that can arise from nematode infestation include stubby root, root lesion and root knot, which produce damaged, underweight, unmarketable product. For the study, four different blocks of soil were allotted to test the effectiveness of Telone and Chloropicrin as well as an untreated control zone. In every single case, the soil treated with fumigant produced a higher marketable yield than the control with the potatoes being divided into four categories of quality: #1’s (the best), Mediums, Jumbos, and Culls (unsellable). Of the four variations of fumigant used, the big winner was TriClor which demonstrated the highest yield per plot of all.

(Citing Dr. Sanchez, the sweetpotatoes were placed in designated bins, in which she examined, counted and took some images of each category across treatments, most marketable are the #1s.  #1s categorized as roots 2 to 3.5 inches in diameter, length 3 to 9 inches, well-shaped and free of defects. Images of medium roots, overall observed high counts across all treatments. Mediums categorized roots are 1 to 2 in diameter, 2 to 7 inches in length. The “jumbos” from each of the fumigant treatments, overall there were low counts. Jumbos are roots that exceed the size requirements of above grades, but are marketable quality. Here are images of culls recovered from each treatment, unmarketable roots. Dr. Sanchez also examined each treatment tubers for any RKN galling/damage. The fumigant treatments did not show any presence, untreated demonstrated minimal damage to the skin of the tubers.)

Ultimately, the study proved the effectiveness of fumigation treatment on sweetpotato yield and quality, suppressing the infestation of nematodes and also proving effective at decreasing the rebound rate for such infestation issues.

(According to Dr. Kristi Sanchez, left graph illustrates average sweet potato yield per plot measured in lbs. By breaking into each marketable category of #1s, mediums, and jumbos. Untreated control had lower weight compared to C-15, Telone, C-35, and TriClor. TriClor alone demonstrated highest yield per plot compared to various fumigant treatments. Examining marketable “mediums” across treatments, grower std displayed slightly higher yield compared to C-35 then followed by TriClor and C-15.)

In the post fumigation root knot nematode evaluation, there was a significant decline in populations among fumigant treatments compared to the untreated control plot. Impressively, there was a 90-99% reduction among fumigant treatments post application.

(The graph and table demonstrate the average number of root knot nematodes detected pre and 4 wks. post fumigation)

As this study has clearly demonstrated, fumigation is a vital pretreatment tool for growers to achieve maximum efficiency and to avoid economic and environmental issues in the future.

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