JoAnne Skelly, Carson City / Storey County Extension Educator, University of Nevada Cooperative Extension, ,

Transcription

1 Date: August 4, 2015 Is it Time to Use a Pesticide? There are many definitions of the word pest, and personal perceptions of pests can often be very different. A pest might be annoying (ants), damaging to plants (rabbits), a health concern (ticks) or a cause for fear (black widow spiders). However, relatively few pests cause significant injury to plants, so pesticides are rarely needed. A pesticide is a substance that destroys, prevents or repels a pest. There are many types of pesticides. For example, herbicides kill plants, insecticides kill insects, fungicides kill fungal organisms, miticides kill mites and rodenticides kill rodents. Often, plant problems in northern Nevada result from non-living factors. These include weather, wind exposure, lack of water or excess water, soil type, soil compaction, poor drainage, improper plant selection for the site, restricted roots or poor cultural practices. Since many plant problems are not caused by living pests, it is important to determine the cause of the problem or symptoms before buying and using a pesticide. First, identify the plant. Some plants are prone to certain insects, such as aphids on ash trees or roses. Some problems are actually nutrient deficiencies. Pin oaks are subject to iron deficiency, which causes the leaves to yellow but veins to stay green. Note the signs of damage. Do you see insects? Or, could site conditions or gardening practices be causing the problem? What characterizes the microclimate, soil type or drainage near the plant? Consider sun, shade and wind exposure. Often, improper watering causes the damage. How do you water, how often, how much and how deeply? If you use a drip system, where are the emitters located, and how many are there for each plant? Is the plant watered all through the year, or just seasonally? Factors people rarely consider when worrying about a plant are the kind of activities that may have occurred near it, such as construction, pesticide spraying, painting or fertilizing. Each may damage plants and cause signs similar to insects or disease. Once you have identified that a pest is present, realize that some level of damage can be tolerated if it s primarily aesthetic and not harming the plant, particularly if the plant is fairly healthy. Before using a pesticide, consider that the problem might go away without taking any action. Try other less-toxic methods of control, for example, spraying plants infested with aphids or spider mites with a strong jet of water. For more information go to

2 Date: August 11, 2015 Root Weevils Eating Leaves Something is eating the leaves on my lilacs, cried the caller. She wondered why the leaves looked like someone had nipped the edges with pinking shears or craft scissors. I knew immediately when she described the angular cuts on the leaves that her plants were being eaten by root weevils. These pesky bugs not only notch leaves, they occasionally come in the house. If you have seen a little black beetle with a long snout crawling around, you have seen a root weevil. Eggs are laid near the crown of plants throughout the summer. These hatch and the larvae develop in the soil. Adults emerge in June to start the process all over. They don t fly, so they crawl up plants to get at the leaves. Photo credit: David Gent, USDA Agricultural Research Service, Bugwood.org. Lilacs aren t the only plants these pests eat. Euonymous, peonies, roses, sand cherries, rhododendrons and many others entice them. Fortunately, the damage is usually more an aesthetic problem than a threat to plant health. I simply tolerate the damage and tell people I have the lacy leaf variety of lilac. It s rare to see root weevils actually eating leaves because they come out at night. One management strategy is to go out in the evening and pick them off your plants by hand. Then drown them in soapy water or squish them. Another nighttime technique is to lay a white cloth under the plant, and gently beat the branches of the plant with a rolled up newspaper to shake the weevils off. They land on the tarp and you can dispose of them. Consider warning your neighbors if you choose this strategy. They might become alarmed if they see a flashlight in your yard at night and hear the sound of trunk beating. Or, they may know your gardening approach by now and just take it all in stride. Some people suggest painting the trunk of the plant with a sticky substance to trap the weevils when they try to climb the bush. However, if you put the sticky goo directly on the trunk, after a while you will have a disgusting mass of dead weevils stuck to it. Try wrapping the trunk with cardboard or tree wrap first and put the sticky substance on it instead. Then, you can remove the cardboard when it is covered with dead critters. Nurseries sell sticky products for this purpose.

3 I don t know about you, but I find my explanation of the lacy variety a much easier remedy. Root weevil damage on lilac. For comparison: Leaf cutter bee damage. Leaf cutter bees are beneficial and use the material they cut out of the leaf to make nests.

4 Date: August 18, 2015 More Pesky Bugs Elm Leaf Beetles Last week I wrote about root weevils eating leaves. This week s pests are the elm leaf beetles. While elms are hardy drought- tolerant trees for arid Nevada, they are plagued by elm leaf beetles every year. By this time of year, the trees look halfdead with white to brown ragged leaves. The problem is the leaves have been skeletonized by the larvae of the beetles. These caterpillar-like creatures scrape off all the green tissue between the veins and leave behind tancolored remains giving a crisp appearance to the leaves. Once the larvae become adults, they chew holes in the leaves. The larvae are black initially, changing to yellowish-green as they feed. The adults are olivegreen with black stripes about one-quarter inch long. Females lay yellowish eggs on the underside of leaves. Before hatching, the eggs turn gray. Although elm leaf beetle feeding ruins the look of a tree, a healthy tree usually survives attack. According to University of California at Davis (UC Davis), Insecticide application is unlikely to be warranted if: beetles and damage were low during the late summer the previous year; or systemic insecticide was properly applied the previous growing season. However, people often can t stand having so many beetles everywhere, dropping on them or onto food and into drinks when dining outside. Some people will cut elm trees down rather than deal with beetles year after year. If you can tolerate these annoying pests and accept the poor appearance of the trees, the simplest course of action is to keep trees healthy with regular watering during dry periods. Also, protect trunks and roots from injury from string cutters, lawnmowers or construction activities. To avoid soil compaction that can damage roots, don t park underneath the trees.

5 If you feel your trees cannot survive the extent of the beetle infestation, there are insecticides available to spray on leaves, to band the trunk or to use systemically. Insecticides include neem oil, narrow-range horticulture oils, pyrethrins, spinosad, carbaryl, dinotefuran and imidacloprid. These are active ingredients, not product names. For detailed information on insecticides, go to UC Davis s website Before you buy an insecticide, read the label to see if it lists elm leaf beetle as one of the pests it controls. Read the label again before application and follow the directions carefully, particularly concerning safety equipment and required protective clothing.

6 Date: August 25, 2015 Plant Now for Fall Vegetables Although numerous pests have been plaguing my garden this year, my gardening spirit can t be stifled. I find myself thinking about planting a fall veggie garden. Many plants will not only tolerate our late summer and fall temperature fluctuations, but will actually thrive. To be successful with a late summer planting for a fall harvest, plant seeds with that reach maturity quickly or buy vegetable starts at local nurseries, if they have them. Also, be prepared to cover crops with row covers, mulch, straw, paper bags, containers, anything to protect the plants when freezes occur. If you have a hoop house or low tunnels, you may be able to grow all winter, depending on where you live. The fastest crop is probably radish, which can mature in as little as 21 days. Bunching onions, regular onions and garlic do best if planted in the fall and need very little care through the winter for a spring harvest. Another way to approach planning a fall harvest is to eat crops at a younger stage such as early lettuces, baby radish leaves and tiny radishes, young spinach, etc. I checked Johnny s Seeds online to see what varieties they had that matured quickly. Other seed companies and our local nurseries will have good seed selections too. Kale is cool season dependable and one of my favorites. Red Russian can be picked for baby greens at 25 days with 50 days to maturity. Starbor and Ripbor can be harvested at 55 days. Toscana, a cold-tolerant Italian variety, is edible at 30 days for baby greens and 65 for mature leaves. Spinach is another good cool season choice. Carmel, Raccoon or Red Kitten can be eaten in 23 to 25 days for baby leaves and 34 to 36 days for mature leaves. Collards, another favorite, are also an option. Beets are good for cool season growing because they get sweeter in the cold. They come in many beautiful colors and the greens are edible too. Red Ace is easy to grow with a crop in 50 days. Merlin takes only 48 days. If you plant Early Wonder Tall Top, you can eat the leaves in 35 days and roots in 55. Explore carrots, turnips, parsnips or rutabagas. Whatever veggies you might plant, be sure to watch the weather and be ready to cover your plants if a freeze is forecast. I actually prefer growing vegetables during the cooler seasons..