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.
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 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…]
After harvest, storing vegetables in optimal conditions is important to ensure the whole season’s hard work has paid off. This article discusses the optimum storage conditions for tomato, pepper, cucumber, watermelon, cantaloupe and sweet corn. Tomato Ideal storage conditions for tomatoes depend on the maturity stage of picking. If tomatoes are picked at mature green, store them in 66 to 70°F with 90 to 95% RH would encourage uniform ripening. Temperatures above 81°F reduce intensity of red color and reduce fruit shelf-life. Green tomatoes are chilling sensitive. If the temperature is below 55°F, fruit may develop chilling injury. Red tomatoes are safe to store at 50°F, however, flavor and aroma may be negatively affected compared to storing them at 55°F. Pepper Optimum storage condition for peppers is 45 to 55°F with 90 to 95% RH. Temperatures lower than 45°F may cause chilling injury. Colored peppers are in general less chilling[Read More…]
Populations of earworms, as evidenced by pheromone trap catches, have not gone to zero as the often due in July. Catches have been fairly low, but moths are still flying and presumably laying eggs. The good news is that in most areas, dent corn is silking, which attracts most of the moths away from our fields of sweet corn and other vegetables. For sweet corn, we would expect pheromone trap catches of less than 10 per night to be safe from damaging infestations of earworm. This is often a good time for growers to avoid the time and expense of spraying their sweet corn. Other vegetable crops such as tomatoes and peppers are less attractive to the moths for egg laying than sweet corn, so they are unlikely to suffer damage when the neighboring field corn has fresh silks present.
The first generation flight of corn earworm moths continues throughout the state. Heaviest populations as evidenced by pheromone trap catches have been in the northwest. This first generation flight should be ending soon. Then we will likely have a lull in catches for a while (several weeks) until the second generation emerges or we get a migratory flight from the southern US. To check moth catches in your area, please visit https://extension.entm.purdue.edu/cornearworm/index_doc.html. Remember that sweet corn that silks prior to silking in the dent corn near your sweet corn field is much more vulnerable to egg laying from the moths. That’s why we recommend spraying if your sweet corn is silking and you catch any moths in your trap. Once the neighboring dent corn begins silking, that corn will be just as attractive to moths for laying eggs as your sweet corn, so the amount of egg laying is diluted.[Read More…]
We are looking for sweet corn growers to participate in our 2017 Vegetable Field Day and Sweet Corn Tasting. Our field day on Aug. 15 at Pinney Purdue Ag Center in Wanatah, will feature tours of tomato production in moveable high tunnels, using both conventional and organic management systems. The event also will include walking tours of sweet corn and pumpkin variety trials, an overview of research findings about the opportunities available through high tunnels, and information about the NRCS program. Attendees will learn about managing pollinators; low-cost high tunnel structures for the home gardener; irrigation solutions; site and structure considerations for new high tunnel users; and finding, preserving, and preparing fresh produce. Private applicator recertification credits (PARP) are anticipated. This event includes a dinner and sweet corn variety tasting. If you would be willing to donate 2 ½ dozen ears of corn, please contact Lyndsay to arrange pick-up/drop-off arrangements. Lyndsay Ploehn, Purdue[Read More…]
Corn earworms are flying. I had 10 in my pheromone trap this morning (June 20). With the surrounding dent corn in most areas far from producing silks, the threshold for spraying silking sweet corn is 1 moth per night, well below what we are catching. So growers who have sweet corn with fresh silks are in danger of suffering serious losses if they don’t control the earworms. Because of problems with resistance to the pyrethroid insecticides, the best products available are Coragen® and Radiant®. Note the limitations on the number of applications or amount of product allowed. You may need both products to complete management on a particular planting. Begin spraying when 30-50% of the plants in your field are silking. Continue to spray every 3-5 days until the silks turn brown. To see corn earworm trap catches around the state, go to https://extension.entm.purdue.edu/cornearworm/index_doc.html.
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