Midwest Vegetable Guide - 2022 - 238

Potato - Diseases
through drip irrigation under unperforated plastic beds.
Before planting, allow product to dissipate for 1 week for
every 10 gals. per acre plus 1 more week. REI: 5-day. IRAC
08F, FRAC M03, HRAC NC. RUP.
Velum Prime (4.16SC) (fluopyram) | 6.5-6.84 fl .oz. per
acre. Apply through overhead chemigation. Do not exceed
13.7 fl. oz. per acre per season. Allow 5 days between
applications. REI: 12-hour. PHI: 7-day. FRAC 07.
Vydate C-LV (3.77WSL) (oxamyl) | 34-68 fl. oz. per acre.
Apply as a banded or shank-injected at-plant in-furrow soil
treatment incorporated 2-4 inches deep with at least 20 gals.
water per acre, or overhead chemigate to deliver rate in 0.5
inch of irrigation water. Do not exceed 8 applications or 306
fl. oz. per acre per season. In Kansas, allow 14 days between
applications and do not exceed 4 applications or 204 fl. oz.
per acre per season. REI: 48-hour. PHI: 7-day. IRAC 01A.
RUP.
Ring Rot of Potatoes - Clavibacter
Bacteria
The ring rot bacterium is easily spread. Although this
bacterium will not survive more than 1 year in the soil (and
thus can be controlled by crop rotation), a farm with ring rot
must conduct a thorough clean-up before bringing in seed for
the next crop. The organism can easily survive the winter in
crop debris or soil on storage walls; seed cutters, bin pilers,
graders, and other handling equipment; tractors, fork lifts and
other vehicles; and on burlap sacks, wooden boxes, or other
containers. If clean seed potatoes contact any of these
contamination sources, the problem can recur.
Non-Pesticide
Use certified disease-free seed. When cutting seed stock, the
cutter should be periodically cleaned and disinfected,
especially when changing seed lots. The first step is to clean
all contaminated surfaces with hot soapy water under
pressure or steam to remove all soil and debris. Then apply a
disinfectant sanitizer. For more information about sanitation,
see Commercial Greenhouse and Nursery Production:
Sanitation for Disease and Pest Management (Purdue
Extension publication HO-250-W), available from the
Education Store, edustore.purdue.edu.
Scab of Potatoes - Streptomyces Bacteria
Scab is more common on potatoes grown in soils with pH
over 5.2.
Non-Pesticide
Avoid fields with a history of nematodes, Fusarium or
Verticillium wilts, droughty, wet, or compacted soils, and
other conditions (such as insufficient nitrogen) that might add
238
undue stress to the crop and increase susceptibility scab.
Acidify soil to a pH between 5.0 and 5.2 with elemental
sulfur in the fall prior to planting.
Silver Scurf of Potatoes -
Helminthosporium Fungus
Use a fungicide when appropriate.
Non-Pesticide
Plant seed pieces certified to be free of disease. Harvest
potatoes as soon after maturity as possible. Rotation to a nonhost
crop 2-3 years.
Pesticide
azoxystrobin products (azoxystrobin) | Use 2 lb. a.i. per
gallon formulations (Quadris) at 0.4-0.8 fl. oz. per 1,000 row
feet. Use 3.3 lb. per gallon formulations (Azteroid) at 0.240.48
fl. oz. per 1,000 row feet. Use 0.83 lb. per gallon
formulations (Dynasty) for seed treatment at 0.10-3.75 fl. oz.
per 100 lbs. of seed. REI: 4-hour. FRAC 11.
White Mold (Timber Rot, Drop, Stem
Rot) of Multiple Crops - Sclerotinia
Fungus
This soil pathogen is long-lived in the soil, and has a wide
host range on broadleaved crops and weeds, including beans,
vine crops, lettuce, tomatoes, peppers, and cole crops. It goes
by other names in other crops, such as Drop, White Mold,
Stem Rot, and Timber Rot.
It is more commonly where humidity and temperatures are
high. The fungus often infects flowers, which then drop off
and infect the stems that they land on. But, the pathogen can
also infect stem tissue around the root crown. The stems take
on a woody appearance and can split open, revealing small
black pellets that are the overwintering body of the pathogen.
Non-Pesticide
Avoid fields with a history of the problem. Rotate to a nonbroadleaf
crop, such as grass grains or sweet corn for >6
years. Avoid excess nitrogen. Reduce overhead irrigation if
disease is present. Prompt destruction of the finished crop
with tillage to rapidly breakdown tissue is an important
method to prevent disease build-up.
Pesticide
Contans WG (5) (Coniothyrium minitans strain
CON/M/91-08) | 1-6 lbs. per acre. Apply immediately after
Midwest Veg Guide 2022
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Midwest Vegetable Guide - 2022

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