94 articles tagged "Insect and Mite Management".

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.

One of the most damaging pests in cucurbit production are cucumber beetles and the bacterial pathogen they transmit (Erwinia trachephila), leading to bacterial wilt.  In the recently released video, Dr. Laura Ingwell from Purdue Entomology demonstrates how to install insect exclusion screens on high tunnels. Such screens are effective at excluding cucumber beetles and the pathogen they transmit from high tunnels. 

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.  

Many of our vegetable crops are attacked by one or more species of flea beetles (Figure 1). All species do similar types of damage, chewing small holes in the leaves. Damage is most important on young plants or transplants, so growers should watch young plants carefully. Fortunately, flea beetles are easy to control. Sevin®, the pyrethroids, and many other products will provide excellent control.

Crucifers such as cabbage, cauliflower, and broccoli are frequently attacked by a variety of caterpillars, with the most important being the imported cabbageworm, diamondback moth, and cabbage looper. The first caterpillar pest to attack crucifers is the imported cabbageworm. The adult stage is the common white butterfly that you will see flying around your field (Figure 1.). They lay eggs singly on the leaves. The larvae are velvety green and move very slowly (Figure 2.). They will consume large amounts of plant tissue and will also contaminate the heads with their feces. Your first indication of activity is when you see the daytime flying butterflies in your field. Once the butterflies are observed, you should begin watching your plants for signs of damage. Plants can tolerate a considerable amount of feeding damage on the leaves before heads begin to form. See the table on page 101 of the Midwest Vegetable[Read More…]

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…]

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,[Read More…]

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Screening can be an effective measure to exclude unwanted pests from colonizing your crops. In high tunnels, one of the biggest challenges to successfully implementing exclusion screening is managing the unintended side effect: reduced airflow. In spring we are clamoring to get inside the warmth that high tunnels provide, but by mid-summer they can become one of the most dreaded environments to work in. The temperatures inside high tunnels beyond mid-June can quickly exceed those suitable to plant growth. The key to maintaining crop production during this time is proper ventilation. Therefore, selecting an insect screen that will effectively exclude pests while minimizing reductions in airflow is crucial. We have been investigating the ability of such screens to keep biological control agents in and cucumber beetles out while maintaining a suitable growing environment for cucumbers, tomatoes and melons. We have looked at three different insect screen sizes over the past[Read More…]

Figure 1. Aphids on kale crop. Photos courtesy Liz Maynard.

Aphids can be one of the most damaging and hard to control pests during the winter months in high tunnels. The first step to managing aphids is to develop a scouting plan. Aphids reproduce clonally and develop quickly leading to very large population build-up in a short period of time. Therefore scouting is recommended at least three times a week. When examining plants be sure to look at the growing point and underside of leaves, where aphids prefer to colonize (Figure 1). Outbreaks commonly begin on the outer rows or the start of the row so these are places to be sure to include when scouting. In the summer months, successful control has been achieved using a soap/mineral oil spray consisting of 1.5% castile soap and 0.25% mineral oil. Cornell University also reports grower success using the biopesticides Mycotrol O and BotaniGard. These are commercially available formulations of the aphid-attacking[Read More…]

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