Georgia: Dealing with a late peanut crop

September 25, 2009 – This year will be Georgia’s latest peanut crop. Peanut planting time has gradually been pushed back to minimize tomato spotted wilt virus infection. A good bit of Georgia’s peanut crop was planted in April before the mid-1990s and the devastating impact of tomato spotted wilt virus. Growers used to begin planting peanuts based on soil temperatures but now wait until the recommended planting dates of May 8-24 to avoid infection and yield losses from tomato spotted wilt virus.

The 2009 peanut crop got off to a poor start in early May as cool temperatures, heavy rains and waterlogged soils delayed crop maturity. The mid-maturity varieties planted in early May are running 135-140 days to maturity but growers should have a hull-scrape run on them to determine ideal harvest time. It is sometimes difficult with so many new varieties to keep the relative maturity range straight under “normal” growing conditions so below is a chart to aid growers.

Early

120-130 days after planting (DAP)

Mid-Maturity

135-140 DAP

Mid-Late

7-10 days later than mid-maturity varieties

Late

2-3 weeks later than mid-maturity varieties

AT-215

Georgia Green

Florida-07

Georgia-02C

Georgia-06G

Georgia-07W

York

Tifguard

McCloud

AT 3085RO

AP-3

Georgia Greener

Georgia-03L

AP-4

I would estimate seventy percent of Coffee County’s peanut crop was planted in the last week of May and first two weeks of June due to heavy rains in mid-May. I would not be surprised if our mid-maturity varieties reach optimal maturity at 130 days or sooner if planted in late May or early June due to the heat unit accumulation in June and July. Many varieties started blooming earlier than normal due to these heat units. On the other hand, the University of Georgia April planted trials are taking 145-150 days for the mid-maturity varieties to reach optimal maturity due to the cool mornings in April delaying bloom initiation.

Once the minimum temperature drops into the lower 50’s and upper 40’s the maturation process will slow but not stop. My experience is that the maturation process does not stop until the temperature drops into the lower 40’s or below. The “normal” minimum temperature in Tifton (based on an 83 year average) is 61 degrees on October 1 and 51 degrees on November 1. If we have “normal” minimum temperatures through October and early November, we should see the maturation of fields planted in early to mid-June continue until optimal maturity is reached.

Peanuts planted on June 15 will be 139 days old on November 1. Any fields planted after June 15 will be at some risk of not reaching optimal maturity if we receive below normal temperatures in November, which is more likely to happen than in October. Growers must be patient with these late planted fields. We should be OK unless we have minimum temperatures like we did in October 2006 and 2008 where we dropped into the 30’s for several mornings in a row.

It will be critically important to stay on a fungicide program up until two weeks of harvest, even in October when we start to get cooler. Occasional rainfall and warm temperatures are still enough for diseases to spread.

A good hull scrape is essential

Even though the crop is running behind schedule it is still important for farmers to take a good hull scrape sample for optimum maturity. Poet Robert Frost once wrote “Good fences make good neighbors” and just as good fences make good neighbors, good hull scrape samples make good results in determining the optimum digging date.

Two or three plants need to be pulled from four to five representative spots in the field. All peanuts expected to be harvested need to be removed and counted from individual plants until the sample has between 180 and 220 peanuts. An ideal sample would have 200 peanuts. The number of peanuts is very important because too few peanuts in the sample would delay the optimum harvest date prediction and too many peanuts would indicate to dig too early.

It is important to remember that the hull scrape method is not an absolute indicator of when to harvest peanuts. Other factors such as weather, acreage and equipment limitations, and poor vine condition due to disease may influence digging date. However, all factors considered, the hull scrape method will give the most accurate prediction of harvest.