Rick Foster

Department of ​Entomology
Area(s) of Interest: Pest Mgmt. Vegetable and Fruit Crops
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Figure 1. Aphids on tomatoes in a high tunnel (Photo credit Wenjing Guan)

We have begun to receive the first reports of aphid outbreaks in high tunnels on tomato, pepper, and cucumber (Figure 1). Aphids are a very common problem in high tunnels because the covering excludes rainfall, which is a major mortality factor for small insects like aphids. Some growers are interested in using biological control in their high tunnels because the ability to contain natural enemies within the tunnels increases the likelihood of achieving control. Based on our experience, we believe that lacewing larvae hold the greatest promise for successful biological control of aphids in high tunnels. Because they don’t fly, they are less likely to leave the high tunnel than many other biological control agents. There are a number of biological control suppliers who can provide lacewing larvae for growers. For growers interested in chemical control, some of the insecticides that could be expected to provide good control and are[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.    

As predicted last week, I have received a number of reports of damage to various vegetables from the root and seed maggots. These pests need to be managed preventively. First, by limiting the amount of decaying organic matter (cover crops, compost, manure) that attracts the flies, growers can reduce the number of eggs laid. Second, by waiting until soils reach 70o F before planting will greatly reduce the damage. Finally, using soil applied insecticides can reduce damage. In many cases, it’s too late for that now. So what can growers do if they have lost a major percentage of their crop from one of these maggot pests? Generally, the only option is to replant. If the crop were seeded with a planter, such as sweet corn, the decision must be made to determine if the crop is worth saving or if a portion of the field needs to be disked[Read More…]

Figure 1. Striped cucumber beetles on melon plants

We found our first striped cucumber beetle on Friday, May 20 and several more on May 23 (Figure 1). Given the cool weather, this is a little earlier than we would have expected. As the temperatures warm up this week, it would not be surprising for cucumber beetles to become very numerous in our melon and squash fields. Striped cucumber beetles are more attracted to squash so growers with those crops should look there first to see if the beetles are active in their area. Growers who direct seeded crops treated with FarMore® insecticide can expect about 3 weeks of control of striped cucumber beetles from that treatment. Growers who grow transplants from seeds treated with FarMore® will receive no benefit from those treatments once plants are in the field because the 3 weeks of control have ended. Likewise, growers who treated at planting with Platinum® or Admire Pro® can[Read More…]

Figure 1. Flea beetles on Brassica (photo credit: John Obermeyer)

Many of our vegetable crops are subject to feeding by one or more species of flea beetles (Figure 1). Flea beetles get their name because they have enlarged hind legs that allow them to jump like fleas. Most species are quite small, and with their ability to jump, often seem to just disappear when disturbed. Flea beetles tend to feed on the leaves, chewing small round holes. When populations are high, the feeding holes with overlap, creating larger holes. Flea beetles tend to be early season pests, primarily because smaller plants are more affected by their feeding. Treatment thresholds vary from crop to crop. For example, eggplants, on of the most commonly damaged vegetable crops, should be treated when there is an average of 4 beetles per plant. For tomato, the threshold is when leaves are 30% defoliated. Crucifers have no particular threshold, so treatment should be made when leaves[Read More…]

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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.

The cool, wet weather we are experiencing is perfect for the root and seed maggots, namely cabbage maggot, onion maggot, and seedcorn maggot. One way of avoiding damage from these pests is to wait until the soils warm up to 70o F before planting, but that is not always possible. The use of row covers early in the season can physically prevent the flies from being able to lay their eggs on the soil near the base of the plants. There are some insecticides available, which vary by crop. Lorsban®, for the crops on which it is labeled, is probably the most consistent of the available insecticides. Capture LFR® has shown decent efficacy on melons and other crops. Melon growers who are putting Admire Pro® or Platinum® on as a soil drench at planting should not expect any control of seedcorn maggots from those applications.

In recent years, protecting declining populations of pollinators has become an important issue. Many of our vegetable crops are dependent upon pollinators for production of fruit. Below is a table that highlights the benefits of honey bees and other pollinators for vegetable production.   Crops That Require Pollinators Crops That Don’t Require Pollinators But Have Better Yields with Them Crops From Which Pollinators Collect Pollen melons eggplant pea cucumber lima bean snap bean squash/pumpkin okra sweet corn pepper tomato Table 1. The importance of pollinators in selected vegetable crop production. There are a number of stresses that harm pollinator populations. Pesticides, although not the most important, are one factor that vegetable growers have some control over. Here are some of the ways that vegetable growers can impact pollinators with pesticides. Applicators apply insecticides to vegetables when pollinators are present, resulting in direct exposure. This can be true for crops that[Read More…]

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…]