[Peanut] Gypsum, Yellow Peanuts, Leafspot, and Rootworms

— Written By Curtis Fountain and last updated by
To:  Duplin Co. Peanut Interests

From:  Curtis D. Fountain

            Agricultural Extension Agent – Field Crops

Since May 23, the Duplin Co. Airport has received 17.44 inches of rainfall (NC State Climate Office).

Gypsum (Calcium Sulfate)

The peanut peg and developing pod absorb calcium directly from the soil, so calcium must be readily available in the soil. Normally, early pegging begins around July 4. Due to water-saturated soils, most peanuts are “behind schedule”. So you are not “behind” as much as you think in terms of gypsum applications. Apply gypsum as soon as you can.

Yellow Peanuts

David Jordan summed it nicely in a July 1 email “What we need is less water and more sun”. Peanut root systems (and nitrogen-fixing bacteria) function poorly in water-saturated soils. Soil pore space is full of water. Allow time for water drainage & oxygen return to soil pore space. Peanuts should then “green up”.

Leafspot Advisory

As in 2012, I will forward the NCSU Leafspot Advisory daily for 3 locations:  Kenansville, Clinton & Kinston. If you want it earlier than I send it, visit the following website:  http://ncsupeanut.blogspot.com/

Except for Bailey and Sugg, NCSU recommends the first leafspot spray at R3 (pegs in soil with swollen tips). For Bailey and Sugg, the 1st leafspot spray is suggested at R3 + 2 weeks (2 weeks after R3). Bravo or Tilt/Bravo (or generics) is recommended for the 1st spray.

 
For subsequent sprays, the advisory can be useful. If management/weather allows, you can shift from a 14-day calendar schedule to an advisory schedule. Considering leafspot and its temperature/humidity requirements, the advisory monitors humidity/temperature at a specific location and notes whether conditions are favorable for leafspot development/spread. You must feel comfortable that your peanut field location shares similar temperature/humidity conditions as the locations being reported. During extended dry conditions over large areas, the advisory can be used to lengthen spray intervals. This can result in fewer total sprays per season and reduce potential spider mite flare-ups (which tend to be more severe during dry conditions).

For each advisory station location, focus your attention on LESD. LESD is the last effective spray date. A fungicide spray is assumed to protect for 14 days so you do not need to spray if you have sprayed since the LESD, even when the advisory says “spray today”.

July 9, 2013 PEANUT LEAF SPOT ADVISORY FOR KDPL
Duplin County Airport (Kenansville, NC)
setDate = 2013-07-03 07:00:00
lethal conditions = false
favorable hours = 41
LESD = 2013-06-22
KDPL Advisory: do not spray today
Growing degree days (base 56) since LESD = 369.3
Growing degree days (base 56) since May 1 = 1083.5
Records count: 142 out of 145
Most recent db ob to 8 a.m. EDT: 2013-07-09 05:55:00

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July 9, 2013 PEANUT LEAF SPOT ADVISORY FOR CLIN
Horticultural Crops Research Stn (Clinton, NC)
setDate = 2013-07-03 07:00:00
lethal conditions = false
favorable hours = 32
LESD = 2013-06-22
CLIN Advisory: do not spray today
Growing degree days (base 56) since LESD = 403
Growing degree days (base 56) since May 1 = 1200.6
Records count: 144 out of 145
Most recent db ob to 8 a.m. EDT: 2013-07-09 07:00:00

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July 9, 2013 PEANUT LEAF SPOT ADVISORY FOR KINS
Cunningham Research Station (Kinston, NC)
setDate = 2013-07-05 07:00:00
lethal conditions = false
favorable hours = 22
LESD = 2013-06-24
KINS Advisory: do not spray today
Growing degree days (base 56) since LESD = 362.1
Growing degree days (base 56) since May 1 = 1202.3
Records count: 96 out of 97
Most recent db ob to 8 a.m. EDT: 2013-07-09 07:00:00

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Southern Corn Rootworms
I am not aware of any 2012 Duplin Co. peanut acreage treated for southern corn rootworms. Should you treat in 2013? The standard treatment is granular Lorsban (or generics) applied in a 16-18 inch band over-the-row at pegging. Wet soil conditions increase the risks for rootworms. Please note 2013 Peanut Information pages 99-100 to assess your risks.

Thanks.

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