Smallflower Buttercup.
A very common winter annual found in untilled fields this spring, smallflower buttercup is a member of the Crowfoot family (not a mustard, like Shepherd’s purse). It forms a small rosette of basal leaves in the fall or early spring. Once warmer weather begins, it bolts and develops small, roundish flower heads on long, narrow stalks. The mature stem has very few leaves for which to intercept burndown herbicides. The good news is that the plant will start to die once seed heads are formed. The bad news is that thick stands (see photo) can attract various insect pests and can be a nuisance to plant through. buttercup2resizedExperienced no-tillers recommend fall herbicide applications for winter annual weeds such as buttercups and cressleaf groundsel that are particularly hard to kill once they form a stalk and flower. Next Fall, apply Princep if rotating to corn in 2009, or Authority, Canopy, Gangster, Scepter or Valor if rotating to soybeans in 2009.
Fall applications of Roundup alone or Roundup + 2,4-D are also effective on many winter.
Wet and Cold Weather.
Some corn fields throughout the region that were planted the last week of April are struggling to emerge. According to my personal calendar, I’ve marked 10 days of the last 20 that it has rained at my house (westcentral Indiana)! And with air and soil temperatures below normal, many are concerned about the emergence of this crop. Assess stands once fields are dry enough to walk across. Stand counts are necessary to get a general idea of how many "normal" plants are present in the field. Most of you know this, but as a quick refresher use the following measurements to get 1/1000 of an acre.
30" rows: count number of plants in 17 ft., 5 inches
36" rows: count number of plants in 14 ft., 6 inches
20" rows: 26 ft, 2 inches
15" rows: 34 ft, 10 inches
To help with replant decisions, I like using the chart on page 11 of the 2008 Purdue Corn and Soybean Field Guide: "Expected Grain Yield due to Various Planting Dates and Final Plant Populations". For example, corn originally planted on April 25 that has an average stand of 24,000 would be at 97% of optimum yield. If the farmer were to replant this field on May 20 and get a final stand of 32,000, he would have 91% of optimum yield, and therefore, would not gain from replanting his field. If replanting an area, tear it up first and then plant it. Spotting-in thin areas with a planter often leads to over-seeding the good rows, creating "twin rows", and headaches later when applying post herbicides or side-dressing nitrogen.
Have a great weekend!
Dan Childs, Agronomist
