603 | Issues | Purdue University Vegetable Crops Hotline

Downy Mildew Update

August 4, 2015

Downy mildew causes bright chlorotic lesions on pumpkin leaves that are limited by veins. Lesions eventually become necrotic. (Photo by Dan Egel).

On July 22, I announced that downy mildew had been observed on watermelon in Knox County in southwestern Indiana. This article https://ag.purdue.edu/arp/swpap/VeggieDiseasesBlog/Lists/Posts/Post.aspx?ID=48 describes the outbreak and management options. Below, I will discuss the whereabouts of additional downy mildew outbreaks on cucurbits. Downy mildew has now been reported on cucumber in Knox and La Porte County Indiana. Downy mildew has been observed on pumpkins in Mason County in central Illinois. In addition, several counties in Kentucky and Michigan have reported downy mildew, primarily on cucumbers. A photo of downy mildew on pumpkin is shown here for reference (Figure 1). You may follow the development of downy mildew of cucurbits on this website http://cdm.ipmpipe.org/.

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Plant Disease Management

Mid-Season Nitrogen Management in Pumpkins

August 4, 2015

By: Dan Egel

Pumpkins are off to good start and vines are starting to run, which means it is time to think about making a sidedress application of nitrogen. Typically, I recommend to split nitrogen applications half preplant and half sidedress. This is especially beneficial given all of our rain this season. If you relied on preplant N alone, with all of the rain, you may very well have lost almost all of your nitrogen with plants just now starting to set fruit. In my personal scenario, on light colored forest soils (common in So. IL and IN, 1.5-2.5 % organic matter) and given no-till with cereal grain residue I generally shoot for around 100-110 lbs. actual N per year (this would be decreased with more fertile, high organic matter soils) with about 50 lbs. of that at sidedress. In a tilled field, you could decrease this recommendation to around 80 lbs. actual N/A per year. This difference can[Read More…]

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Cucurbits / Pumpkins

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Soil Fertility and Fertilizers

Sunburn on Vegetables

August 4, 2015

By: Dan Egel and Liz Maynard

Vegetables such as this watermelon may become sunburned if lack of foliage cover exposes the fruit to excess sun and heat. (Photo by Dan Egel)

Loss of foliage due to poor growing conditions or disease can cause fruit to be exposed to the sun. Hot temperatures and direct sunlight can lead to areas of the fruit that appear bleached or sunburned. Sunburned fruit may not be marketable. To reduce the probability sunburned fruit, every effort should be made to maintain foliage throughout the season. Early wet weather encouraged foliar disease and recent hot, dry weather may have restricted foliar development. Orienting vegetable plantings to minimize damage from the prevailing winds and providing windbreaks such as strips of rye or wheat may help to reduce sunburn. Several products are available that are labeled for use as a preventive for sunburn. These products may be broken into two groups: kaolin (clay) based products and calcium carbonated based products. Kaolin based products include Surround®. Some Surround® products are labeled for use as sunburn protection, while others are not. For example,[Read More…]

Crops

Cucurbits / Tomato / Vegetable Crops - General / Watermelon

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Climate and Weather / Crop Culture

Soil Solarization

August 5, 2015

By: Dan Egel

Tomato growers who utilize high tunnels to reach early markets often find that there are few economic alternatives to tomato. Therefore, many growers grow tomatoes after tomatoes instead of rotating to a different crop. The repeated cropping of tomato in the same area can lead to disease problems such as Fusarium crown rot and white mold (timber rot). Soil solarization takes advantage of solar radiation to heat the soil to temperatures that are lethal to many fungal pathogens, nematodes, and weed seeds. In Indiana, soil solarization is not always practical for field use since the period where soil solarization would be useful, summer, is also the period where most growers must produce crops. The use of soil solarization in high tunnels, however, may be more practical since these crops are produced earlier than field crops. Additionally there is chance for greater heating of the soil if the high tunnel vents[Read More…]

Crops

Tomato / Vegetable Crops - General

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Plant Disease Management / Protected Culture and Season Extension

Spider Mites

August 5, 2015

By: Rick Foster

We have received a number of reports of outbreaks of spider mites, primarily in watermelons and in high tunnels. The problems in high tunnels are not unexpected because one of the primary causes of mortality in mite populations is rainfall washing them off the plants and, of course, that is lacking completely in high tunnels. With all the rain we have had, it’s a little surprising that we are seeing problems in watermelons, but the older I get, the less I’m surprised by how infrequently arthropods behave the way we expect them to. In both scenarios, we don’t really have treatment thresholds for mites. Generally speaking, if populations are increasing, they need to be controlled. Once the decision to treat has been made, that’s where things get very different. In watermelons, we have a variety of pesticide choices. See page 115 of the Midwest Vegetable Production Guide (ID56) for the[Read More…]

Crops

Cucurbits / Solanaceous Crops / Tomato / Watermelon

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Insect and Mite Management / Protected Culture and Season Extension

Corn Earworm

August 5, 2015

By: Rick Foster

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.

Crops

Corn / Sweet Corn

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Insect and Mite Management

Fall Armyworm

August 5, 2015

By: Rick Foster

Fall armyworms have completed their annual trek from the Gulf Coast to the Midwest. Fall armyworm larvae will feed on all aboveground parts of the sweet corn plant, during all stages of growth. The damage to the foliage is much more severe than with European corn borer. Larvae will feed from within the whorl of the plant until the tassel starts to emerge, at which time they will move to other plant parts, including the ear. Larvae will enter the ear either through the tip, similar to corn earworm, or they may come through the husk into the side of the ear. The best time to control fall armyworms is during the late whorl stage, before they tassel emerges and they start to move. Pyrethroid insecticides such as Warrior®, Brigade®, Mustang Max® and Hero® will provide excellent control. Most growers will want to save their more expensive Coragen® or Radiant® treatments for earworm control[Read More…]

Crops

Corn / Sweet Corn

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Insect and Mite Management

Green Stink Bug

August 5, 2015

By: Rick Foster

I have seen more green stink bugs this year than at any time in my career. I have no logical explanation for their abundance. It was thought that as the invasive brown marmorated stink bug became established, it might outcompete the native stink bugs such as the green stink bug, causing numbers to decrease. However, this year, brown marmorated stink bugs have been relatively uncommon, and green stink bugs seem to be everywhere. Stink bugs feed with their sucking mouthparts and are likely to feed on a wide variety of vegetable crops, including cabbage, sweet corn, cucumber, bean of all types, okra, mustard, peas, peppers, and tomato. Check the Midwest Vegetable Production Guide (ID-56) for your particular crop for insecticide recommendations.

Crops

Beans (Green, Wax, Snap) / Cabbage / Cole Crops / Corn / Cucumbers / Cucurbits / Greens and Salad Crops / Legume Vegetables / Lima Beans / Mustard / Okra / Other Vegetables / Peas / Peppers / Solanaceous Crops / Sweet Corn / Tomato

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Insect and Mite Management

Goodbye Endosulfan

August 5, 2015

By: Rick Foster

Growers should remember as of July 31, 2015, it is illegal to use endosulfan on any crop other than pineapple or strawberry. By July 31, 2016, all use of this product will be cancelled. Endosulfan in an organochlorine insecticide, the same class as DDT, and was first produced in the US in 1954. It has been a very effective insecticide for over 60 years, but is quite toxic to humans, so it has outlived its usefulness. Fortunately, we have a variety of newer, safer products available today.

Upcoming Events

August 5, 2015

By: Liz Maynard

Pinney Purdue Vegetable Field Day and Sweet Corn Sampler. Thursday, August 13, 2015. 4:00 P.M. – 8:00 P.M. CDT. Pinney Purdue Ag Center, 11402 S. County Line Rd., Wanatah, IN. Plot tours include soil health management and disease suppressive soils, tomatoes and peppers in high tunnels, and sweet corn varieties. Private Applicator Recertification (PARP) Credit available. To register, visit http://tinyurl.com/no6tosr or contact Lori Jolly-Brown, ljollybr@purdue.edu, or 765-494-1296. Beginning Farmer Tours. Free farm tours and networking events sponsored by Purdue Extension and Local Growers Guild. For more information and to register contact the Purdue Extension Education Store at www.edustore.purdue.edu or 888-EXT-INFO. August 18: Redbud Farm, home of Caprini Creamery, Spiceland, IN. Breakfast, networking, lunch and tour. September 8: Growing Places Indy, Indianapolis, IN. Lunch, networking session, tour. Urban produce farm with raised beds, u-pick, and greenhouses. September 14: Morning Harvest, Palmyra and Hardinsburg, IN. Breakfast, networking session, lunch and tour. Developing[Read More…]

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Events

Issue 603 - August 6, 2015

Downy Mildew Update

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Mid-Season Nitrogen Management in Pumpkins

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Sunburn on Vegetables

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Soil Solarization

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Spider Mites

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Corn Earworm

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Fall Armyworm

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Green Stink Bug

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Goodbye Endosulfan

Upcoming Events

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Issue 603 - August 6, 2015

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