agriculture

By Patrick Porter and Ed Bynum, Extension Entomologists in Lubbock and Amarillo, respectively.  The August 25th edition  of this newsletter discussed how our mCry3a Bt corn was no longer able to control western corn rootworm in an area from Hart, Texas, north to the top of the Panhandle. In that newsletter, even though we were seeing all of the classic signs of resistance, we used the term �probable resistance�, only because our laboratory assays on field collected beetles will not be completed until next year.  In addition to mCry3a, that newsletter suggested that since there is cross resistance between all of the Cry3-type toxins (mCry3a, eCry3.1Ab and Cry3Bb1), none of these toxins could be expected to provide good control of western corn rootworm. Dr. Aaron Gassmann at Iowa State University, a leading authority on corn rootworm resistance, said, �Cry3Bb1, mCry3A, and eCry3.1Ab all appear fairly similar to the rootworm. Resistance to one is likely to confer resistance ...

Dr. Chris DiFonzo, Entomologist at Michigan State University and author of the Handy Bt Trait Table, and I got a note from a corn seed dealer a couple of weeks ago concerning the removal of some single toxin Bt corn hybrids from the market after 2019. Apparently there was a letter circulating from one of the seed companies to this effect, and he wanted to know whether it was true and, if so, why it was being done - some of his customers really like their single toxin hybrids.  It is true, and it is a good and necessary thing. Back when Bt corn was first introduced, most hybrids had only a single toxin for caterpillar pests, and, a few years later, if there was a corn rootworm toxin it was single as well. A few more years down the road, seed companies began selling �pyramids� of toxins; a combination of two or more toxins targeted at a pest. Not only did this improve efficacy, but it also slowed the rate of resistance development as explained in the following scenario.  If inse...

A "new" insecticide option is being tried and promoted on the High Plains for control of some caterpillar pests, especially sorghum headworms (corn earworm and fall armyworm). There are some appealing aspects to this, but there is a lot we don't know as well. Dr. Ed Bynum just posted a nice summary of the history of these insecticides based on nucleopolyhedrovirus (NPV), how they work, and some aspects of application and labeling.  Insecticidal Virus Products for Pest Control: What are the Latest Facts , Panhandle Pest News, 7 November 2018. Because these are live viruses and spread in the field, the minimum plot size needed for research is very large. We would be interested in trying one or both of these headworm products on large fields next year. By large I mean way bigger than we have at the Experiment Station. There would be large blocks of treated and untreated sorghum, and ground application equipment would be essential.