31 articles tagged "Corn".

Figure 2. Fall armyworm feeding on kernels.

Fall armyworms (Figure 1) are only able to survive the winter in extreme southern US, along the Gulf Coast and in Florida. Fall armyworms tend to migrate northward gradually, with each successive generation moving several hundred miles further north. They reach Indiana every year, but their populations are unpredictable in numbers and location. This week we have received reports of fall armyworm infestation in corn from southwest Indiana and northern Elkhart County, so they are throughout the state. However, infestations tend to be spotty, with individual fields or even portions of a field showing damage, with neighboring fields uninfested. Fall armyworms will feed on corn at all stages of development and will feed on all above ground plant parts (Figure 2 and 3). However, their late arrival in Indiana (July-August) means that we are mostly concerned about feeding on kernels in the ear. Because of the higher value of the crop, sweet corn,[Read More…]


Pheromone trap catches of corn earworms have been relatively low in most areas of the state, with northern Indiana having the highest counts. Counts from the Purdue research farms can be seen at https://extension.entm.purdue.edu/cornearworm/index.php. Remember that as the field corn surrounding your sweet corn begins to silk and be attractive to the earworm moths for egg laying, the threshold for treatment in your sweet corn rises from 1 moth per night to 10 moths per night. I would like to express one note of caution about using thresholds. We recently had one trap that on seven consecutive nights caught 9, 7, 5, 9, 6, 7, and 7 moths. On none of these nights was the threshold of 10 moths reached. However, on two night 9 moths were caught and at least 5 were caught on every night. I think it is reasonable to assume that the accumulation of eggs laid[Read More…]


I continue to catch low numbers of corn earworm moths in my pheromone trap. Although the numbers are low, growers with very early sweet corn that is in the reproductive stage should be alert for potential damage. The threshold for spraying sweet corn that matures prior to field corn silking is only one moth per night. My cooperators at the Purdue Ag Centers around the state are putting up their earworm pheromone traps today (June 6), so by the time you receive this newsletter, we should have data available on moth catches around the state, which you can access at https://extension.entm.purdue.edu/cornearworm/index.php. As I suggested in the last edition of the Vegetable Crops Hotline, I have found corn earworm larvae feeding in the whorl of my knee high sweet corn, planted April 18.


I am continuing to catch a small number of corn earworms in my trap. Usually we talk about earworm moths being attracted to silking corn to lay their eggs. However, moths will lay eggs on whorl stage sweet corn and the larvae can cause damage (Figure 1 and 2). The larvae will often feed inside the whorl, similar to European corn borer feeding. This damage is usually not very serious, but growers with very early sweet corn should be aware of the potential.    


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I caught my first earworm (Figure 1) moth in a pheromone trap last week. Earworms are very polyphagous, meaning they will eat lots of different plants. I suspect that any females that are flying are laying their eggs on wild plants of some sort and not on the seedling stage sweet corn or dent corn that is present in fields around the state. If you are one of the aggressive growers who grows sweet corn in the greenhouse and transplants it to the field to get that early market, your plants (unless they are covered by row cover) may be subject to earworm egg laying and feeding. This generation of larvae will be long gone before ears begin to form, so your only concern will be the foliar feeding damage and not ear infestation.


Three species of seed and root maggots attack vegetables in Indiana. The seedcorn maggot (Figure 1) feeds on seeds and seedlings of sweetcorn, cucurbits, lima and snap beans, peas, and other crops. Cabbage maggots can cause serious damage to transplants of cabbage, broccoli, cauliflower, and Brussels sprouts and make the fleshy roots of radishes, turnips, and rutabagas unmarketable. Onion maggots are pests of seedling onions, developing bulbs and onions intended for storage. Seedcorn maggot flies emerge in April and May and lay eggs preferentially in areas with decaying organic matter. Fields that are heavily manured or planted to a cover crop are more likely to have seedcorn maggot injury. Maggots burrow into the seed and feed within, often destroying the germ. The seeds fail to germinate and plants do not emerge from the soil, leaving gaps in the stand. When infested seeds germinate, the seedlings are weak and may die.[Read More…]


One way insects communicate with individuals of the same species is with pheromones. Pheromones are volatile chemicals released by an insect that usually can be detected only by individuals of the same species. There are a number of different types of pheromones, but the most common type is the sex pheromone. Usually the females will emit a tiny amount of a chemical that attracts the male to her and increases the likelihood of mating. Because the chemical is volatile, air currents carry it. The male detects the pheromone in the air with receptors on his antennae. He then flies upwind to find the source of the pheromone, a prospective mate. The chemical compositions of pheromones for a number of pest species have been identified and synthetic copies can be produced in the laboratory. Synthetic pheromones can be used in conjunction with traps to catch male insects. Listed below are some, but[Read More…]


Photo by Dan Egel.

The relatively cool weather Indiana has experienced this summer may be responsible for more observations of northern corn leaf blight (NCLB) on sweet corn than normal. The primary symptom is the cigar shaped lesion that ranges from 1 to 7 inches in length (see Figure 1). The lesions may range from tan to gray in color. Under conditions of high humidity, olive-green fungal spores may be produced on the lesion surface. Symptoms of NCLB are frequently observed late in the season when days become cooler. Yield losses are possible if lesions reach the ear leaf or higher during the two weeks before or after tasseling. NCLB can be managed by a combination of crop rotation, fall tillage, resistant hybrids and fungicide applications. Crop rotation and fall tillage help to minimize crop residue that might harbor the fungus that causes NCLB. Choose hybrids resistant to NCLB when possible. When it is necessary[Read More…]


​Catches of corn earworm moths in pheromone traps are gradually increasing. I had 18 in my trap this morning (August 18). The gradual increase is indicative of the local population emerging. We can expect them to continue to gradually increase for most of the remainder of the season. What we have not had is the massive influx of moths from the south, likely due to the lack of tropical storms in the Gulf of Mexico and few storm fronts coming northward from the Gulf States. With populations as they are currently, most sweet corn growers should have little problem managing this pest. A regular spray program should provide nearly perfect control. There are three main factors that you have control of that determine the level of control you will receive. You need to have the right chemical in the right place at the right time. I recommend using Coragen® and[Read More…]


​Pheromone trap catches for corn earworms continue to be very low. Again, this is a time when growers can save a lot of money and time by monitoring their pheromone traps and not spraying. I harvested untreated sweet corn on Friday, July 31, and had over 98% clean ears and the few that were damaged had very few kernels fed upon and in 400 ears, we found not a single earworm. On the other hand, moth flights are likely to pick up any time between now and about August 20, based on 28 years that I have been monitoring their flights in Indiana. Regularly checking your moth catches will help you to know when the moths have arrived and when you need to increase your management activities. The treatment threshold now is 10 moths per night, because of the maturity level of field corn nearby.


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