40 articles tagged "Corn".

After weeks of successive trap catches in the double digits, our recent catches have gone down. Be sure to check the CEW trapping website for updates daily. At this point in the season, when field corn is in the silking stage, the threat to sweet corn, and potentially hemp, goes down. The current action threshold is 10 moths in the trap per night. Spray decisions should be made based on the closest trap location. In the table online, if no value is entered, it means the trap has not been emptied. A zero will be present in the data table if the trap was checked and there were no moths present. As field corn dries out and is no longer silking, the threat to flowering hemp and silking sweet corn goes back up. The trap catch threshold lowers to 1 moth per night. Closely monitor your crop and the surrounding[Read More…]



The sweet corn variety plots at Pinney Purdue provide a good chance to observe sweet corn insects. In late July I observed two caterpillars that surprised me. The first was European Corn Borer (ECB), in the tassel where they are often found (Figures 1 & 2). It was a surprise because I have seen many fewer of these in the sweet corn plots in recent years. I understand from the entomologists that it is due to the widespread use of Bt field corn that has resulted in much lower populations of ECB. The week of Aug. 19 I observed an ECB egg mass on a flag leaf and a young larva on the ear (Figures 3 & 4). The second late July observation was a corn earworm (CEW)–the insect itself is not surprising, but it was in the tassel! (Figures 5-8). I have previously only seen them in ears. The[Read More…]


Southern rust pustules on corn leaf, and chlorosis on the underside of the leaves. Pustules generally form and erupt on upper surface. (Photo Credit: A. Sisson, Iowa State University

This article is modified from Darcy Telenko’s article about field corn in a recent Purdue Pest and Crop newsletter. Southern rust of corn is normally a disease of tropical areas. During summer months, however, the fungus which causes southern rust, Puccinia polysora, may move into Indiana or other Midwestern states.  Southern rust has officially been confirmed in Posey and Vigo County. If you think you have this disease contact me or submit a sample to the PPDL https://ag.purdue.edu/btny/ppdl/Pages/Submit-A-Sample.aspx Southern rust pustules generally tend to occur on the upper surface of the leaf, and produce chlorotic symptoms on the underside of the leaf (Figure 1). These pustules rupture the leaf surface and are orange to tan in color. They are circular to oval in shape. We are seeing a lot of common rust as well and both diseases could be present on a leaf. Common rust will form pustules on both sides[Read More…]


Fig. 1 Corn earworm adult on silk. Photo courtesy John Obermeyer.

We have begun our state-wide trapping and monitoring program for corn earworm (Figure 1). The latest trap catch information can be found here. Traps have been placed at each of the eight Purdue Agricultural Centers throughout the state. Trap catches at the reporting farms are already in the double digits. Please refer to E-31 to learn more about corn earworm identification and management. Management and insecticide sprays target the eggs that are laid, preferably on fresh corn silk. If no field corn in the area is silking, which is true for most this year, use a threshold of 1-3 moths per night per pheromone trap. You only need to spray your sweet corn if it has silk present. When field corn begins to silk and green silk is present the threshold increases to 10 moths per night. Eggs are laid individually on developing silk. They hatch within 2-5 days and[Read More…]


Corn earworm moth numbers have been relatively low this season until recently, as numbers have exploded in pheromone traps. These moths will lay their eggs on numerous crops, with late-market sweet corn being particularly vulnerable at this time. Tomato and pepper growers should also be aware of the potential for earworm (also called fruitworm) damage, especially if these crops are surrounded by cornfields that are drying down  and are no longer attractive for egg laying.  


Several caterpillars in the ear can be very similar in appearance and habits, so identification to species of some of the worms in ears can be tricky. Note that, in general, you cannot use overall body color or damage for identification. Some identification tips, though not foolproof, appear below for the corn earworm, western bean cutworm, fall armyworm and European corn borer. We suggest you inspect cornfields soon before the larvae leave the ear and pupate.   This article was previously published in the Purdue Extension Pest & Crop Newsletter.


Figure 1. Corn Earworms

Now is a good time to begin your plans for managing corn earworms (Figure 1) in your sweet corn. Below are several tips that will help you in this process: Make sure you have a corn earworm pheromone trap and earworm pheromones. See the article below for details. Consider planting Bt sweet corn, especially for your later plantings that will be harvested in late July and August. If you choose to do so, use varieties that contain two sources of the Bt protein, including the Vip3A protein found in the Attribute II series. Varieties that only contain Cry1Ab proteins do not effectively control earworms in most instances. If you use a Bt variety, maintain a normal insecticide spray program. It’s not a good idea to think that the Bt genes will provide complete control. The combination of Bt and insecticides will help overcome the high populations of earworms late in[Read More…]


The USDA lab out of Wooster, Ohio is interested in surveying Indiana sweet corn for virus. They are especially interested in sweet corn near johnsongrass, but other fields are ok too. If you are interested, please let me know or contact Mark Jones, USDA Agronomist,mark.jones@ars.usda.gov, (330) 202-3555 ext. 2837. Your participation would be pretty simple: one time when the corn is 15 to 30 inches tall you would collect ten leaf samples on a field transect and also a sample of any odd looking plants and mail them to the USDA lab for analysis. USDA would mail you a packet with sample bags and instructions and mailing materials. If you are interested, but would rather have someone else collect the samples, I can check with a local county Extension educator to see if they would be interested in collecting the samples. Thanks for considering this!


Southern blight causes red-orange pustules primarily on the upper surface of sweet corn.

Southern rust of corn is normally a disease of tropical areas. During summer months, however, the fungus which causes southern rust, Puccinia polysora, often moves into southern areas of the U.S. This summer, southern rust has been observed in at least 11 Indiana counties. Symptoms of southern rust include raised structures called pustules. If rubbed with a finger, the spores in rust pustules will come off leaving a stain on one’s hand. Southern rust develops rust pustules primarily on the upper leaf surface (Figure 1). Common rust typically has rust pustules on both upper and lower leaf surfaces. In severe cases, southern blight can cause rust pustules on ear husks and leaf sheaths. Late in the summer, dark pustules may be formed which are called telia. It is possible to confuse southern rust with other diseases, therefore, a confirmation by the Purdue University Plant and Pest Laboratory is advised. The[Read More…]


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