Rick Foster

Professor
Department of ​Entomology
Area(s) of Interest: Pest Mgmt. Vegetable and Fruit Crops
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In southern Indiana, we are between generations of striped cucumber beetles. That doesn’t mean there are none out there, but numbers are lower than they were and lower than they will be. The second generation should be coming out soon. Northern areas are a little behind. The biggest concern we have with the first generation or overwintering cucumber beetles is their ability to feed on seedlings and to transmit the pathogen that causes bacterial wilt to cantaloupes and cucumbers. For the second generation, we are less concerned about bacterial wilt and more concerned about feeding damage to the fruit, particularly watermelons and cucumbers. If you are seeing beetle feeding on fruit, you should probably apply an insecticide to protect the fruit. If not, you are probably safe not spraying. For later planted pumpkins, the biggest concern is feeding on the plants in the seedling stage. Once the plants get larger,[Read More…]


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…]


Figure 1. Hornworm feeding on tomato leaves in a high tunnel.

One of the most impressive insect pests that we deal with on vegetables are the hornworms (Figure 1 and 2). These two species, tomato and tobacco hornworm, can reach up to 4 inches long and consume massive quantities of foliage and fruit. In recent years, we have seen damage in high tunnels that is more serious than we normally see in field situations. The good news is that despite their size, hornworms are relatively easy to kill. A wide variety of insecticides will control them. See pages 143-44 in the Midwest Vegetable Production Guide for choices. As with most pests, it is better to treat when the hornworms are small because they are easier to kill and because you can avoid most of their damage. Hornworm damage is usually fairly easy to see, either because of the defoliation or the frass (insect poop) that they leave behind. So, scout regularly[Read More…]


Figure 2. Squash bug nymphs (photo credit John Obermeyer)

Squash bug is the most consistent insect pest of squash and pumpkins and is the most difficult to control (Figure 1 and 2). The key to management is early detection and control of the nymphs. The adults are extremely difficult to kill. Foliar insecticides should be applied to control the nymphs when you have more than an average of one egg mass per plant. When you find egg masses, mark them with flags and check every day or two to see when they hatch. When many of the egg masses are hatching, that is the time to begin application. Since eggs are laid and hatch over an extended period of time, several applications may be required. Brigade®, Mustang Max® and Warrior® have provided excellent control.


I have received some reports of Colorado potato beetles damaging both potatoes and tomatoes, including tomatoes in high tunnels. Both the adults and larvae are voracious feeders. As with most pests, it is best to get potato beetles under control before the populations get too high. Also, killing small larvae is easier than killing large ones, so spraying earlier will provide better control. We have had numerous reports of resistance to the pyrethroids in Indiana, so I generally don’t recommend those products. If you try one and it works, then you probably don’t have a resistant population at this point. For most of the state, I recommend one of the following products, Admire Pro®, Agri-Mek®, Assail, Coragen®, Exirel®, Radiant®, and Rimon®. Note that Coragen® and Radiant® cannot be used in high tunnels.


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. Spider Mites damage on cucumbers in a high tunnel

We have received a number of reports of spider mite problems lately. Some of them have been on crops grown in high tunnels, particularly tomatoes and cucumbers. High tunnels are the perfect environment for mites because it is hot, which means they reproduce faster, and the mites are protected from rainfall, which is a major mortality factor for them. So far, our efforts to develop biological control strategies for mites in high tunnels have been unsuccessful. Therefore, chemical control is often required. One important point is that you should start the management process early, before the mites get out of hand. Don’t wait until you have a disaster before you take action. Check the Midwest Vegetable Production Guide for the miticides labeled for use on your crop, and then check the table on page 45 to see if it can be used in greenhouses or high tunnels. Most of the[Read More…]


Figure 1. Stripped cucumber beetle (Photo by Wenjing Guan)

Populations of the overwintering generation of striped cucumber beetles are just about at their peak levels right now (Figure 1.). For muskmelons and cucumbers, this generation is the one that we worry the most about in terms of transmitting the pathogen that causes bacterial wilt. As a result, our spray threshold is relatively low, 1 beetle per plant. Watermelons and most squashes and pumpkins are not susceptible to bacterial wilt so we use a higher threshold, 5 beetles per plant. The pyrethroid insecticides provide excellent control. Because these insecticides are harmful to pollinators, growers should wait until late afternoon or evening when the flowers have closed and the pollinators have left the field before spraying.


Figure 1. Seedcorn maggot in a melon stem

I received my first report of seedcorn maggot damage on cantaloupes last week (Figure 1 and 2). A grower in northern Indiana reported losing 90-95% of his plants. Given the cool, wet growing conditions, it wouldn’t be surprising to see more reports of this type for a number of crops, including melons, beans, corn, onions, and crucifers. Some of these crops have insecticide alternatives that can be used at planting but other, like melons, have no such option. The best approach for melon growers is to either wait for warmer weather or cover the young plants with row covers to physically exclude the flies from laying eggs. If you have had plants killed by maggots, wait at least 3 days before replanting in the same holes to give the maggots time to complete their development. See the article from Issue 625 (published on April 13, 2017) for more details.


Figure 1. Black cutworm larva (photo by John Obermeyer)

We have had substantial black cutworm moth (Figure 1.) catches in our pheromone traps. Black cutworm moths typically lay their eggs on winter annual weeds growing in un-tilled fields. When the eggs hatch, the larvae will begin feeding on the weeds. Then, when you kill the weeds with either tillage or a burndown herbicide, the larvae are left there with nothing to eat. If you wait a couple of weeks to plant, they will probably starve to death. If you plant sooner than that, they will just be really hungry and will readily attack a variety of crops. The pyrethroid insecticides provide good, economical control.