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Soil Health and Insect Scouting 2020

December 31st, 2020 | Posted by miker in Special Projects

North Slope Farm 2020 Insect Scouting Report

Scouting and Report by Paige Sirak

(Apologies – Photos were not loading properly, and will be added asap.)

From late June to August of 2020, I scouted insects on three major crops to monitor the effects of the reduced tillage practices on soil biology, namely the insect population. These crops included summer squash, green beans, and carrots. While each vegetable faced its own issues, there was a common presence of beneficial insects among all three.

The summer squash had two main obstacles in the insect world: squash bugs of varying life stages and adult cucumber beetles. The squash bug grows quickly in size and goes through multiple life cycles in a growing season. They are a piercing-sucking insect that causes interruptions in the transport of nutrients to the plant and often leads to chlorosis, wilting, and death of a leaf or a plant (Hahn). This type of damage was commonly seen in the summer squash, especially in the more mature crops (see Figure 1). Although the squash bug caused visible damage, the mature plants were able to cope with the loss of a few leaves in favor of focusing their energy on producing the fruit. Secondly, the cucumber beetle was present on almost every summer squash that was scouted. The cucumber beetle is a biting-chewing insect that feeds on leaves, stems, flowers, and the fruit of the plant, leaving holes and brown spots (see Figure 1). This damage was not severe, but the cucumber beetle is also known to carry and transmit disease (Snyder). Beyond its feeding habits, its high mobility most likely played a part in the spread of powdery mildew among the later generations of summer squash. The powdery mildew, which is transmitted through small spores, had affected much of the later generations of the squash (see Figure 1)(Wyman). However, as these later generations were mature, they were still able to yield fruit without much loss. While there was a significant presence of harmful insects, the summer squash produced marketable fruit and was not critically damaged.

The second crop, green beans, was only slightly affected by insects but was more heavily affected by disease. The bugs that were often found on the beans were flea beetles. These biting-chewing beetles left small holes in the leaves (see Figure 2). The damage was typically reduced to 10-15% of the leaf and did not cause any severe issues. Previously, flea beetles had affected napa cabbage on the farm, but as that crop was not present, the population was not as significant. The beans were facing issues with a fungus, bacteria, or another disease that caused them to brown, curl, and shrivel (see Figure 2). Due to the lack of severe harmful insect presence, it can be concluded that the green beans’ slight struggle was with another foe.

The carrots, the third crop monitored, were experiencing significant rotting damage due to what was previously believed to be the carrot rust fly maggot. The carrots that were monitored often had tunnels that were eaten away and rotting (see Figure 3). In order to identify this pest, the carrots would be pulled and observed, and the soil would then be sifted through to look for any living insects, specifically larvae or maggots. The damage was found mostly on the more mature carrots. While the affected location of damage fluctuated, it became clear that, as the carrots matured, the marred surface appeared on the top/middle of the carrot, as opposed to near the tip. It was this fact that allowed an expert at a NOFA event to identify the pest to be the carrot weevil. The damage between the carrot rust fly and carrot weevil are nearly identical with the exception of the location of the affected area. As carrot weevils are notoriously difficult to get rid of, this issue is expected to persist and harm future carrot crops.

While these crops experienced some unfortunate insect-related issues, there was also a strong presence of beneficial species that were common to all three vegetables. One insect often found was the ladybug in varying life stages (see Figure 4). Ladybugs typically consume harmful pests such as aphids, whiteflies, mites, and cabbage moths (Telkamp). Further beneficial insects included pollinators, such as varieties of bees, butterflies, and moths (see Figure 4). The presence of flowers being grown for market and the wildflower populations on the farm ensured that pollinators were frequent visitors. Additionally, native milkweed was found between fields, which supported lots of these beneficial insects. It served as a habitat for monarch butterflies and caterpillars, as well as for other pollinators and bugs looking for a wild strip of land.

At the end of this project, it became apparent that while the squash and beans interacted with insects in their own ways, they were able to overcome these obstacles and yield a sufficient crop. While the conclusion to the mystery of the carrot weevil was not what we had been hoping for, it helped me gain real-life experience for practices such as the scientific method and research. I’m very grateful for the opportunity to engage in hands-on experience and to have worked with such wonderful and knowledgeable mentors.

Works Cited

Hahn, Jeffrey. 2020. “Squash bugs in home gardens.” University of Minnesota Extension.

Snyder, William E. 23 December 2019. “Managing Cucumber Beetles in Organic Farming Systems.” eOrganic.

Telkamp, Mike. n.d. “What do Ladybugs Eat?” HGTV.

Wyman’s Home and Garden. 1 July 2018. “Powdery Mildew and How to Control It.” Wyman’s Home and Garden Blog.

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