31 articles tagged "Corn".

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…]


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.


Figure 1. Corn Earworms

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…]


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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.


Figure 1. Armyworm damage corn leaves.

We have had major flights of armyworm moths (Figure 1.), as evidenced by pheromone trap catches. Catches have been highest in the northeastern portion of the state. Armyworms prefer grasses but will feed on other crops if necessary. During outbreak years, the infestation usually will start in pastures or other grassy areas. Once the armyworms have consumed most of the available leaf tissue, the larvae will march as a group (hence the name) looking for something else to eat. The next crop consumed may be wheat or early corn. When populations are heavy, the damage can be devastating. Fortunately, these kinds of outbreaks occur quite rarely. The last major outbreak we experienced was in 2001. If you have early-planted sweet corn, it would be wise to watch grassy areas for armyworm damage. If you see evidence of a problem there, watch your sweet corn for any signs of activity. The[Read More…]


Corn earworm flights are quite variable around the state, but are generally heavy. Counts in pheromone traps are higher in the northern part of the state, with the LaPorte County trap reporting 1422 moths over a 7 day period last week. That’s about 20 X the threshold level. As I wrote in the last newsletter, growers need to be spraying frequently when silks are green during this period of time. If you are growing one of the Bt varieties, especially in the northern part of the state, I would still recommend at least a moderate spray program to ensure that you get the results you are looking for.


After a season of relatively low corn earworm activity, pheromone trap catches have taken a dramatic turn upward, especially in the northern half of the state. Catches of 100-200 moths per night in the trap are not uncommon currently. Keep in mind that the threshold for treatment is 10 moths per night, so these catches would be 10-20X the threshold. At this point, growers with late sweet corn should be beginning treating when about 30-50% of the plants are showing silks. Sprays should be applied every 2-3 days until silks turn brown. It takes 3 days for eggs to hatch so a reasonable question would be, why spray every 2 days?  Really what it becomes at this point is a numbers game. Even the best insecticide applied at the highest rate with excellent coverage will not provide 100% control. When counts are near the threshold the number of escapes is[Read More…]


Corn earworm moth catches continue to be quite low in most areas of the state. Typically, we see an upsurge in activity during the first two weeks of August. With populations as low as they are and most field corn still with attractive silks, sweet corn growers can get by with minimal spray programs now. However, growers should be diligently watching their pheromone traps for the next generation to arrive. It is not unusual for trap catches to go from near zero to in the hundreds per night literally overnight. This type increase if usually associated with some sort of tropical disturbance in the Gulf of Mexico but can also occur when storm fronts move up from southern locations.


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