Utah Plant Pest UTAH PESTS Diagnostic Laboratory USU Extension Fall 2020 QUARTERLY Vol. XIV NEWSLETTER IN THIS ISSUE Dahlia Mosaic Virus Utah Study of Hemp Pests Native and Exotic Parasitoid Wasps of BMSB in Utah Spider Mites Active with Hot, Dry Hemp (Cannabis sativa) was grown as future, we expect to see more pests become Conditions a federally-recognized Utah commodity established. Common pests are listed on the starting in 2019, primarily for production next page, with images of pest damage, on of CBD oil. That fall, we surveyed hemp page 3. Got “Worms” in producers and learned that plant pests Your Berries? were a contributing cause of harvest On the farms we visited, it was apparent losses in 2019 (average of 5% loss) and that other factors superseded plant pests Tomatillo Trouble- that producers were looking for pest in reducing yield, such as plant deformities Maker identification and management information. due to genetic variation (see images on next page), plant nutrition, watering, lack of Utah Pests then formed a project team root growth, and weeds. Abnormal growth Asian Giant Hornet (see box) and received funding from Utah from genetic variation was due to starting Look-alikes State University Extension to help fill these crops from seed rather than from clones. information gaps. One part of the project We tested dozens of these plants for viruses IPM in the News is to collaborate with hemp producers to (curly top, tobacco mosaic, and others), identify the major pests of field-grown hemp and all were negative. through farm surveys in 2020 and 2021. NEW MEDIA The three most common hemp varieties Invasive Pests of Landscape In summer 2020, the team identified 12 grown on the cooperator fields were Trump Trees in Utah (book) cooperator farms and scouted for insect (also known as T1), Abacus, and Berry and disease activity with up to six visits per Blossom, with about 14 other varieties also How to Detect and Treat Early Blight (video) farm. We searched plants for abnormal grown. There were no differences in pest symptoms and where appropriate, problems or genetic variation between How to Spot and Treat collected associated plant tissue and/or varieties. Cucurbit Powdery Mildew (video) arthropods for diagnosis in the Utah Plant Pest Diagnostic Lab. The Pests of Hemp project team consists How to Spot and Control of Marion Murray (project lead and field Flea Beetles (video) Although our survey identified several plant survey), Claudia Nischwitz (plant pathogen Verticillium and Fusarium pests, we quickly learned that none of them diagnosis and cultivar testing), Ricardo Wilts in Cantaloupes (video) have yet become major pests in Utah. Few Ramirez and Lauren Gates (cultivar testing diseases were seen, and the most common and field survey), Zach Schumm (arthropod arthropods were beneficial insects such as diagnosis), and county Extension faculty big-eyed bugs, minute pirate bugs, damsel (Jody Gale, Cody Zesiger, Ruger Carter, Ben bugs, assassin bugs, and lady beetles. Scow, Mike Pace, Candace Schaible). As Utah's hemp acreage expands in the continued on next page Study of Hemp Pests, continued UTAH PESTS TEAM Most Common Pests Found in the 2020 Survey, and Their Abundance Diane Alston ARTHROPODS Entomologist Head, Dept. of Biology Ant, pavement - Tetramorium caespitum 2% of farms; some plant losses [email protected] Aphid, cannabis - Phorodon cannabis 5% of farms; no significant damage 435-797-2516 Beet webworm - Loxostege sticticalis 2% of farms; no significant damage Marion Murray Corn earworm - Helicoverpa zea 2% of farms; minor flower damage IPM Project Leader Utah Pests News Editor Flea beetle, elongate - Systena elongata 33% of farms; minor foliar damage [email protected] Grasshoppers (multiple species) 50% of farms; no significant damage 435-797-0776 Leafhoppers (unidentified) 50% of farms; no significant damage Claudia Nischwitz Leafminers (old damage; unidentified) 2% of farms; no significant damage Plant Pathologist [email protected] Lygus bugs – Lygus spp. 90% of farms; no significant damage 435-797-7569 Stink bug, one-spotted - Euschistus variolarius 1% of farms; not widespread Ricardo Ramirez Thrips, western flower - Frankliniella occidentalis 90% of farms; no significant damage Entomologist Two-spotted spider mite - Tetranychus urticae 2% of farms; no significant damage [email protected] 435-797-8088 Wireworms – Limonius spp. 1% of farms; not widespread DISEASES Zach Schumm Arthropod Diagnosician Crown gall - Agrobacterium tumefaciens 1% of farms; not widespread [email protected] 435-797-2435 Fusarium wilt and crown rot – Fusarium spp. 5% of farms; some plant losses Powdery mildew - Erysiphe sp. 1% of farms; not widespread Lori Spears Prof. Practice Associate Prof. Pythium crown rot – P. aphanidermatum 33% of farms; some plant losses USU CAPS Coordinator [email protected] Examples of Poor Vigor Due to Genetic Variation From Seed-Grown Hemp 435-797-0354 Nick Volesky Vegetable IPM Associate [email protected] 435-797-0319 Utah Plant Pest Diagnostic Lab BNR Room 203 Stunting associated with upward-curled and Some plants start from seedlings with thin, Utah State University twisted foliage. curled leaves, and remain that way. 5305 Old Main Hill Logan, UT 84322 To subscribe, click here. All images © UTAH PESTS and USU Extension unless otherwise credited. Stunted but otherwise healthy-looking plants Plants with chlorotic foliage were tested were commonly seen. These plants often for nutrient deficiencies, and many results utahpests.usu.edu developed chlorotic foliage as they matured, showed adequate nutrient content. and produced low yields. continued on next page Utah Pests Quarterly Newsletter / Fall 2020 / page 2 Study of Hemp Pests, continued Examples of Pests and Symptoms Found on Field-Grown Hemp in Summer 2020 Flea beetles were found on just a few farms, along with Thrips feed by piercing the plant surface with their mouthparts symptoms of their feeding damage. and sucking the contents of cells, cauuseing white spots. Beet webworm (shown above) and corn earworm were the Leafminer damage was sporadic, with no larvae found within only caterpillar pests found in 2020. the mines to allow species identification. Pavement ants were a problem on a few farms, not only Crown gall is a bacteria-caused disease found on one farm. disturbing the soil, but feeding on the crown, causing dieback. Affected plants were stunted and some died. Fusarium was found on a few farms, causing a wilting in a Pythium crown rot is a deadly disease tied to saturated soils. portion or in the entire plant. Marion Murray, IPM Project Leader www.utahpests.usu.edu Utah Pests Quarterly Newsletter / Fall 2020 / page 3 PLANT PATHOLOGY NEWS AND INFORMATION Dahlia Mosaic Virus Dahlias are popular in Utah’s cut flower industry, but can be affected by viruses. The USU Extension Plant Pathology lab identified several viruses in dahlia plants collected from Utah farms as well as in tubers and seed purchased from suppliers. One of the most common viruses was Dahlia mosaic virus (DMV). DMV is a DNA virus in the genus caulimovirus. It is transmitted by aphids and carried over in seed and tubers. There are three strains: DMV-D10, DMV-Holland, and DMV-Portland. To date, the most common strain found in Utah is DMV-D10, followed by DMV-Holland. DMV- Portland occurs only occasionally. In some plants, two or even all three strains have been identified (Table 1). The Symptoms of Dahlia mosaic virus include stunting (top strain found so far in seed is DMV-D10 (Table 2). left), vein-clearing on leaves (top right), color breaking on petals (lower left), and mosaic patterns (lower right). DMV causes many different symptoms, and it is currently unknown what affects symptom development. Some plants Table 1. Distribution of DMV Strains Among may show no symptoms at all while others are stunted, Sample Types have mosaic patterns, vein clearing on leaves, or develop necrotic lesions. In some varieties, leaves are distorted and Seed Tuber Leaf All Types color breaking may occur on infected flowers. Moreover, H only 0% 25% 12 % 14% stunted plants frequently do not produce marketable flowers. P only 0% 3% 0% 1% In some cases, the symptoms could be caused by several D only 54% 11 % 8% 20% viruses, including Tomato spotted wilt virus or Tobacco streak virus. To determine the virus and prevent its spread, HP 0% 0% 2% 1% farmers must submit plant samples to a plant pathologist for HD 0% 14% 29% 17% molecular- or antibody-based testing. PD 0% 3% 0% 1% DMV can spread during the growing season by aphids that HPD 0% 0% 10% 5% acquire the virus while feeding on infected plants, called Total 54% 56% 61% 58% secondary spread. The aphids deposit the virus in healthy plants during feeding. Insecticides to control aphids are not Note: H=Holland, P=Portland, D=D10 very effective since the aphids do not stay on the same plant Table 2. Incidence of DMV Among Sample Types for a substantial amount of time. Seed Tuber Leaf All Types Many unanswered questions about DMV exist, and Drs. H Total 0% 39% 53% 36% Claudia Nischwitz and Melanie Stock will address some of them in summer 2021, including transmission of the virus P Total 0% 6% 12 % 7% during cut flower harvest, associating DMV strains with D Total 54% 28% 47% 42% specific symptoms, and a greenhouse trial to determine susceptibility of popular dahlia varieties. To prevent DMV, start with healthy, virus-free tubers or seed. contact Nischwitz ([email protected]) or Stock However, because these are difficult to source, testing your ([email protected]). own stock is an option. Farmers that plan to overwinter tubers for next year’s cut flower production can get up to Tyson Compton, Technician, Claudia Nischwitz, 20 plants tested at USU, paid for by a grant.