Laura Ingwell

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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…]

As part of a multi-state effort being headed by Dr. Ian Kaplan at Purdue University in the Department of Entomology, we are investigating how to best manage insect pests on cucurbits, in our case watermelons, while having the least possible impact on pollinators. The research is being funded through the USDA/NIFA Specialty Crop Research Initiative. The premise of this research is based on the fact that neonicotinoid insecticides, which are a versatile and powerful pest management tool, have been implicated as a factor contributing to pollinator declines. Thus, farmers growing pollinator-dependent crops—including watermelons—are confronted with a potential trade-off between two competing aspects of crop production: effective pest suppression and successful pollination. Our objective here is to identify insecticidal management strategies that simultaneously optimize pest suppression while minimizing non-target exposure to cucurbit pollinators. To achieve this objective, we are currently looking for producers to collaborate with members of the Entomology Department[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…]

There is a variety of commercial suppliers to choose from when purchasing predatory insects and parasitoids for biological control. Some of them rear the insects themselves and others are distributors for some of the larger rearing facilities in Europe and Canada. There are some key things to consider when choosing a supplier. The first of which may be shipping dates and ordering deadlines. Depending on the predators being purchased, they typically ship one day a week (multiple for organisms such as predatory mites) and therefore there are strict ordering deadlines the week prior. In general biological control needs to be implemented when pests are first detected, and at low levels, through active scouting efforts. If pests are already at damaging or outbreak levels alternative interventions (insecticidal soap or chemical application) to knock back the populations may be necessary prior to releasing predators for long-term control. Either way, it is important[Read More…]

Figure 1. A ladybug feeding on aphids

Supplementing the natural enemy population to control insect pests, i.e. augmentation biological control, is of interest to many high tunnel producers. Augmentation biological control has proven very effective at managing a number of greenhouse pests and there are a variety of commercial suppliers. For high tunnels, the greatest challenge is keeping the released predators or parasitoids inside the tunnels and choosing agents that are effective under high temperatures, during the peak of the growing season. We have evaluated some of the more common control agents in high tunnel cucumber and tomato production. The convergent ladybug, Hippodamia convergens, is not grown in a growth facility but rather caught in the wild in the western U.S. (typically California) and shipped throughout the US for control of aphids in particular. They are a fairly inexpensive predator (1500 for about $15.00), the immature form (larvae) and adults feed on aphids (Figure 1). However, you[Read More…]

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…]