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Western Plant Diagnostic Network1 First Detector News A Quarterly Pest Update for WPDN First Detectors Winter 2017 edition, volume 10, number 1 Dear First Detectors, In this Issue We have gone from 5+ years of drought with water-starved Page 1: Editor’s comments trees, vineyards, and gardens to an overabundance of water Pages 2 – 3: Drought, Rain, in a very short time. The lead article discusses working with Snow, Flooding, and Plants wet soils and the judicious selection of nursery stock. Hawaii is right in the middle of the Pacific and is indeed the crossroads of that ocean. Because it is the crossroads and Pages 4 – 5: Hawaii: was historically isolated, it receives more than its share of Paradise for Invasives invasives plants, animals, insects, and plant pathogens. The Hawaii Department of Agriculture (HDOA) has sent a list of Page 6 – 7: Five Fusarium the latest invasive pathogens. Nevada once again Species Isolated from Hemp contributes to the further knowledge of diseases of Cannabis sativa. And there is yet another invasive insect Pages 8 – 9: Olive Bark Beetle pest of olives in California, this time a woodboring bark Found in California beetle found in Riverside County, California. Monday, March 20th is the first day of spring, time to get Contact us at the WPDN Regional busy in orchards, vineyards, fields, and gardens! Keep an eye Center at UC Davis: out for invasives, who are also waking up! Phone: 530 754 2255 Email: [email protected] Please find the NPDN family of newsletters at Web: https://wpdn.org Editor: Richard W. Hoenisch Newsletters @Copyright Regents of the University of California All Rights Reserved J. B.J. Wheatley Gypsy moth about to emerge from pupa Western Plant Diagnostic Network News Drought, Rain, Snow, Flooding, and Plants 2 In the Summer 2016 WPDN newsletter featured Western forest mortality from the effects of five years of drought, warmer winters, and the subsequent explosion of woodboring beetle populations. What a difference a very wet season makes! The West Coast dams and aquifers are being recharged, as well as the Colorado River basin. The Southwest is still parched, but hoping for a good August monsoon season. With all these blessings, standing water and wet soils can be also be cold and anaerobic or hydric. Trees planted in cold, wet soils may be in anaerobic conditions and experience root rots. Seeds planted into cold soils may sit and wait or may germinate but grow very slowly. In these very early stages of life, seedlings are highly susceptible to soil borne pathogens that cause root rot and damping off, such as Rhizoctonia and Pythium. Signs that trees and crops are infested with Rhizoctonia and Pythium are: Plants are stunted. Root tips are brown and dead. Plants wilt at mid-day and may recover at night. Plants yellow and die. Brown tissue on the outer portion of the root easily pulls off leaving a strand of vascular tissue exposed. To prevent these early season root rotting pathogens, wait to plant warm season crops and gardens until soils have warmed to the recommended temperature and are moist but not heavily wet. This year, it may be necessary to start seeds indoors and transplant them into the garden when outdoor conditions improve. In addition many simple structures like cold frames and walls of water can help warm soils and protect plants. Black plastic mulch also warms soil in the root zone. By growing plants in a raised bed, gardens have improved drainage even in wet weather. Seeds coated with a fungicide treatment will be protected at the earliest stages of growth. Tree and vineyard growers should always obtain their planting stock from reliable and certified nurseries. In addition to the soil fungi, plant viruses, not visible in dormant planting material, could infect the woody plant and manifest later in growing trees and vines. Retail plant nurseries have to stay on top of their pests and disease issues. Choose to buy from places that seem to be always monitoring their product. Despite what appears to be close monitoring, even the most scrupulous shop owner can miss a problem. It is up to you to check your individual plants for any visible insects or disease problems. Turn the leaves over and inspect for visible insects hiding there. Look for chewed or damaged spots on the leaves and stems, and pick only the individual plants that have nothing. A disease can be in the form of mold, mildew, fuzzy, discoloration, slime, or powder. Lastly, do not buy a flat or 6 pack with a diseased plant in it. More than likely, the other 5 plants have been inoculated. You don’t want to introduce Phytophthora, Fusarium , and Verticillium into your garden soil. When you do find a plant that seems to be harboring some sort of insect or disease, please let the shop owner know (in a quiet, respectful tone), and do not handle the pot yourself if possible. Plant disease, insect pests, nematodes, mites, weeds, snails, and slugs do spread! Many years ago one of our UC Davis Plant Pathology professors moved to a new house. He was very fond of cactus and replanted his new garden with several species. He inadvertently introduced Phytophthora cactorum on a n infested cactus and it destroyed his entire collection! Western Plant Diagnostic Network News 3 What to Look for in a Healthy Plant 1. Quality of Nursery or Garden Center: Take in an overview of the plant department. Look to see that the majority of the plants seem healthy and well cared for. If there are a lot of wilted or browned plants in one section, chances are good the rest of the plants are not being given great care. 2. Foliage : Evaluate the condition of your specific plant. Are the leaves green, shiny and lush? Steer clear of any plants that are wilting or yellowing. Stressed plants may not recover. This is especially important if you are buying annuals and vegetables. These plants won't have time to rally. 3. Shape: Consider the shape of the plant. Is it compact and full, with multiple stems? Taller is often not better. It could mean the plant has been straining for light and has grown thin and spindly. 4. Insects & Disease: Inspect closely for signs of insects or disease. Check both sides of the leaves and the potting soil. Signs can include: blackened areas, holes, spots, mushy areas, stickiness and distortions. 5. Root System: Don’t neglect the roots. If the plant is pot bound and the roots are growing out of the bottom, the plant may be stressed and take time to recover. If there aren’t many roots and the plant lifts out very easily, it was probably recently repotted and could use more time to become garden worthy. 6. Stem Damage: If the plant has a thick or woody stem, make sure there are no cracks or scars. Even prior damage can weaken a plant. 7. Weeds : Weeds in the pot are competing with the plant for nutrients. They also signal some neglect on the part of the nursery staff. The last thing you want is introduce a new weed into your garden. 8. Root Ball: When buying a balled-and-burlapped tree or shrub, the root ball should feel solid. If it appears broken, there’s a good chance the roots have had a chance to dry out and the plant will suffer. 9. Buds & Flowers: Although it's tempting to want to buy a plant that is already covered in flowers, plants in bud will transplant and thrive better than plants in flower. Besides, the existing flowers will fade quickly. You'll get a longer bloom time at home if you purchase a plant that is in bud. 10. When all is said and done: Allow ample time when shopping for landscape garden or vegetable nursery plants. Taking a little extra time to choose your new plants carefully is sure to result in your buying beautiful, healthy specimens. Western Plant Diagnostic Network News Green Nursery Thumb 4 Hawai’i: Paradise Is Also Paradise for Invasives! In the Winter 2016 edition, page 9, we discussed a fungal disease on the native Hawaiian tree, Ohi’a lehua, Metrosideros polymorpha, in the family Myrtaceae, called Rapid Ohi’a Death, or ROD. This disease is caused by a fungus, Ceratocystis fimbriata. This disease was originally described in Hawai’I on sweet potato in 1890. It is an invasive species that eventually began to infect O’hia. Please see Rapid O'hia Death Update from the University of Hawaii, Manoa. This map traces the disease from 2014 to February 2017. The Hawaiian Islands, like Guam, the Samoan Islands, the Marianas, and islands in general, are targets of invasive species. Because islands developed their own particular ecologies, invasives tend to take over these fragile ecologies. Oftentimes the introduced species is better equipped to survive and competes with the native species for food, light or other resources. For example, the strawberry guava tree is one of Hawaii's worst invasive species. It is dangerous because it crowds out native plant species, breaks up natural areas, disrupts native animal communities, alters native ecosystem processes like water production, and provides refuge for alien fruit flies that are a major pest of Hawaiian agriculture. An excellent book on island ecologies is: Invasive Species, by Daniel Simberloff. The Hawaiian Islands have been ground zero for invasives. Mosquitoes were introduced, supposedly in water casks brought in by ships. Hawaii has a growing invasive species crisis affecting the islands' endangered plants and animals, overall environmental and human health, and the viability of its tourism and agriculture-based economy.

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