Laura Ingwell

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Figure 3. Webbing produced on heavily infested cucumber leaves by two-spotted spider mite.

Despite the wet start to the summer that we are experiencing, we have some growers reporting spider mites in field watermelons (Figure 1). This pest is typically associated with hot, dry weather and can be especially problematic in crops grown under protection, such as in high tunnels. Spider mites often move into a field from an adjacent fencerow or rye strip. Two-spotted spider mites (Figure 2.) are most commonly a problem on watermelon and cucumbers in high tunnels, but also affect muskmelons. They can be detected by observing the yellowish discoloration on the upper side of the leaves or using a 10x hand lens and scouting on the underside of the leaf for the pest. Alternatively, you may use a white sheet of paper and tap the leaves above the paper to dislodge the mites; you will see them moving about on the sheet of paper. Because mites often migrate[Read More…]


Figure 1. A cucumber plant grown in a high tunnel died because of bacterial wilt.

Bacterial wilt is one of the most destructive diseases in high tunnel cucumber production. The reason bacterial wilt is so important is because, like other wilt diseases, it ties up with the entire vascular system of a plant, causing systemic effects (Figure 1). The relatively less important roles that other cucumber diseases play also make bacterial wilt the major limitation for high tunnel cucumber production in Indiana. For example, common cucumber diseases such as angular leaf spot, anthracnose and Alternaria leaf blight seldom occur in a high tunnel scenario; improved resistance to powdery mildew was observed in some of the newly developed cucumber varieties; downy mildew in general does not occur in Indiana until end of the high tunnel cucumber production season. The causal organism for bacterial wilt of cucumbers is Erwinia tracheiphila. After the bacteria enter the plant vascular system, it multiplies quickly. As a result, it interferes with[Read More…]


One can hardly glance at the news recently without noticing an item about the health of bees and other pollinators. We can all agree on the importance pollinators play in the health of our planet and the critical role honey bees and bumble bees play in agriculture. There is no doubt that populations of honey bees in particular have been in decline over the last several years. The multiple reasons for the decline are not as clear. This article will address the role that fungicides may play in bee health. There are many possible reasons for the decline of bee populations. Pesticides have been implicated in bee declines. Most experts would agree pesticides may play a role in bee population declines. The type of pesticide that is most often implicated in bee declines are the insecticides. This makes sense: bees are insects. There is less known about the role that[Read More…]


Figure 3. A cucumber beetle on the 0.7 x 1.0 mm screen (photo credit: John Obermeyer)

One of the most problematic insect pests that organic vegetable growers have to deal with is the striped cucumber beetle. The insect feeds on all the cucurbit crops, but can be particularly devastating to muskmelons and cucumbers because those two crops are susceptible to bacterial wilt of cucurbits, which is caused by a bacterium carried by the beetles. The only way to avoid this devastating disease is to prevent the beetles from feeding on the plants. There are no effective organic insecticides for managing striped cucumber so we have to look for alternative methods. Row Covers: Row covers can be used to physically prevent beetles from feeding on the plants. To be effective, these need to be placed over the plants immediately after transplanting or before direct seeded crops emerge. The edges of the row covers should be sealed with soil to prevent the beetles from crawling under the fabric[Read More…]


Entomologists are looking for growers willing to participate in research examining the detection and distribution of striped cucumber beetles. We would like to visit your fields on multiple occasions this year to count the number of cucumber beetles we encounter in your crop. If you grow slicing cucumbers in the field, and are interested in helping to improve our sampling recommendations for this pest, please contact Dr. Laura Ingwell at (765) 494-6167 or lingwell@purdue.edu


It’s that time of year, where we are prepping high tunnels and getting back into the full swing of production, slowly, here in the Midwest. Many of you have already begun to transplant and may have encountered your first pests on these new crops. Aphids are one that remain a problem in high tunnels, and may even have plagued your winter production (Figure 1,2,3). Some keys to preventing or controlling these pests rely first on sanitation and then careful scouting. Try to remove any green bridge material that may already be infested before transplanting into the space. This includes weeds, lingering winter crops or residues. Having a week without vegetative hosts should get rid of any overwintering residents. After transplanting scout diligently, at least weekly, or more often on susceptible young transplants. Aphid infestations tend to begin on the growing points or younger tissues of the plant. Be sure to[Read More…]


Figure 2: A tomato with tomato spotted wilt virus has necrotic ring spots.

While many virus diseases affect pepper and tomato plants, in the Midwest, the most common virus diseases of these two crops are tomato spotted wilt virus (TSWV) and Impatiens necrotic spot virus (INSV). These diseases are usually observed in greenhouse or high tunnel situations. The two viruses, TSWV and INSV are closely related. In fact, at one time, they were both considered TSWV. Therefore, the symptoms, biology and management of these two diseases are similar. This article discusses the symptoms, biology and management of these two diseases. Both TSWV and INSV affect many hosts, including vegetables and flowering ornamentals. Symptoms vary according to host, stage of plant affected and environmental conditions. Both diseases can cause stunting, yellowing, necrotic rings, leaf mottle and more. Figure 1 shows a tomato leaf with necrotic rings caused by TSWV. Figure 2 shows a pepper transplant with ring spots caused by INSV. Additional symptoms may[Read More…]


Figure 3. Webbing produced on heavily infested cucumber leaves by two-spotted spider mite.

It is that time of year again, when the two-spotted spider mites (Tetranychus urticae; TSSM, Figure 1), and other mite species, show up in full force and wreak havoc on fruit and vegetables. These pests are very inconspicuous and often go unnoticed until the resulting damage appears. For TSSM this includes the webbing produced on heavily infested leaves or to the more trained eye, the characteristic yellow speckles or mottled symptoms on the upper surface of the leaves (Figure 2 and 3). The mites can be found on the underside, feeding with their sucking mouthparts. Cucumber, especially in organic production, can be the most susceptible. However, this pest feeds on a wide range of plants including tomatoes, melons, peppers, strawberries, apples, pears and grapevines, as well as flowers and field crops. Regardless of your production technique, an intervention is almost always necessary to control TSSM. In high tunnels in particular,[Read More…]


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. 


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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…]