Crops are growing rapidly and questions regarding expected end-of-season yields and soil water and nitrogen (N) status in the fields become very timely. A group of faculty, researchers, farm managers, and students from Iowa State University have developed a free, publicly available online platform (http://crops.extension.iastate.edu/facts/) to provide answers to these questions.
Integrated Crop Management News
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Corn rootworm egg hatch in Iowa typically occurs from late May to the middle of June, with an average peak hatching date of June 6 in central Iowa. In 2016, the average hatching date will be slightly behind normal and approximately the same time as in 2014 and 2015. Development is driven by soil temperature and measured by growing degree days. Research suggests about 50 percent of egg hatch occurs between 684-767 accumulated degree days (base 52°F, soil). Most areas in Iowa have reached peak corn rootworm egg hatch or will within a few days (Fig. 1).
Soil testing is a useful and commonly used diagnostic tool for making phosphorus (P) and potassium (K) fertilization decisions. Tissue testing has been suggested for decades as another tool for these and other nutrients. However, tissue testing has not been widely implemented for P or K in Iowa or the North Central region because of inconclusive results from limited field calibration research based on crop yield response. Iowa State University (ISU) has no P or K tissue test interpretations for any crop. Therefore, research was conducted to evaluate the value of tissue testing for P and K in soybean.
As the season progresses and crop protection products are applied, the handling and disposal of all those pesticide containers deserve some attention.
Soil testing is a useful and commonly used diagnostic tool for making phosphorus (P) and potassium (K) fertilization decisions. Tissue testing has been suggested for decades as another tool for these and other nutrients. Tissue testing has not been widely implemented for P or K in Iowa or the North Central region, however, because of inconclusive results from limited field calibration research that has associated yield response. Iowa State University (ISU) has no P or K tissue test interpretations for any crop. Therefore, research was conducted to evaluate the value of tissue testing for P and K in corn.
Western and northern corn rootworm are major corn pests in Iowa and surrounding states (Photos 1 and 2). Farmers have seen several management changes, including the release of four Bt-rootworm traits to suppress corn rootworm larvae since 2003. Although both species are persistent pests, western corn rootworm is particularly adaptable. The Gassmann Lab at Iowa State University (ISU) has demonstrated western corn rootworm resistance to all Bt rootworm traits in Iowa.
Every year we evaluate commercial fungicides on corn applied at V5 alone, VT-R1 alone, or both growth stages for disease control and effect on yield. The trial was done in collaboration with the farm managers at four Iowa State University (ISU) Research and Demonstration Farms (Table 1). The trials are laid out in a randomized complete block design with four to six replicates. Plot sizes are 10 foot (4 rows) wide and 30-100 foot long. Hybrids varied by location.
Tracking degree days is a useful tool to estimate when common stalk borer larvae begin moving into cornfields from their overwintering hosts. Foliar applications, if needed, are only effective when larvae are migrating and exposed. Start scouting corn for larvae when 1,300-1,400 degree days (base 41°F) have accumulated. Southern Iowa counties reached this important temperature benchmark over the holiday weekend (Fig. 1), and therefore scouting for migrating larvae should begin now to make timely treatment decisions.
Aphids are common insects to see in field crops, especially in alfalfa. In Iowa, there are at least four aphid species that can persist on alfalfa. A recent report of pea aphids near Clarion, IA from field agronomist Angie Rieck-Hinz prompted me to write this article. Learning to distinguish aphids in alfalfa takes a little practice, but is worth knowing for making sound treatment decisions.