Benton County Hort Report

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Phillip Hensley
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May Issue Peach Leaf Curl Oak Gall New Pre-Emergent Poisonous Hemlock Benton County Hort Report Upcoming Events May 1 FSMA Training Clarksville, AR Private Applicators License Benton County Extension

1 May Issue Peach Leaf Curl Oak Gall New Pre-Emergent Poisonous Hemlock Benton County Hort Report Upcoming Events May 1 FSMA Training Clarksville, AR Private Applicators License Benton County Extension Office, 6:30pm May 3 High Tunnel Workshop Lonoke, AR May 5-6 Tree Climbing Competition Crystal Bridges Bentonville, AR May 12, 9am Irrigation and Tomato Pruning Demonstration Helping Hands Garden Bentonville. AR May 22 FSMA Training Yellville, AR Photo credit: OSU Extension Hello from your county extension office. Each month I am going to pull together some of the top horticulture concerns for you in Northwest Arkansas. As always please contact me with any questions or concerns. Ryan Neal Peach Leaf Curl by Ryan Neal and Sherrie Smith Pictured above, this is one of the easier diseases to diagnose and is common on both ornamental and fruiting peaches. Unfortunately once symptoms of peach leaf curl are evident, it is too late to spray during the current season. Spores from the fungus Taphrina deformans overwinters on twigs and bud scales. Infection occurs at bud break early in the spring during cool, wet weather. Blister-like swellings, curling, thickening, puckering, and discoloration of the leaves are the first symptoms of Peach leaf curl. Affected areas may turn pink, red or yellow. In severe cases, defoliation occurs along with substantial yield loss. Peach leaf curl is easily controlled with one well-timed fungicide application in the fall after 90% of the leaves have dropped, or very early in the spring before the buds begin to swell. Chlorothalonil or copper sprays are effective. It is too late for chemical control this spring, but if only a few leaves are infected, they may be handpicked and destroyed to reduce inoculum levels.

Oak Gall and Anthracnose by Ryan Neal and Mary Hightower Photo credit: Arizona Extension (top), Purdue Extension (bottom) One of the most common calls I received last year had to do with white oak

Jon Barry, extension forester for the University of Arkansas System Division of Agriculture, said that two seasonal syndromes common to oak trees in the Arkansas summer, jumping oak gall and oak

2 Oak Gall and Anthracnose by Ryan Neal and Mary Hightower Photo credit: Arizona Extension (top), Purdue Extension (bottom) One of the most common calls I received last year had to do with white oak trees appearing sick or in decline. Jon Barry, extension forester for the University of Arkansas System Division of Agriculture, said that two seasonal syndromes common to oak trees in the Arkansas summer, jumping oak gall and oak anthracnose, have begun to rear their heads in certain areas of the state. In the grand scheme of things, neither of these are that bad, Barry said. They re just ugly. The first, jumping oak gall, is caused by Neuroterus saltatorius, one of about 250 species of gall wasps found on oak, he said. The gall typically a series of small, scab-like cysts that cover the leaves serves as an incubator for the tiny, stingerless gall wasp larvae, which are deposited in the early spring. Barry said that many times, an accumulation of galls will cause leaves to prematurely brown, but the syndrome is seldom aggressive enough to harm the tree itself. Jumping oak gall is so named because as the larvae matures inside the gall, their active movements can cause a fallen gall to actually move or jump, not unlike the phenomenon of Mexican jumping beans, Barry said. Barry said there is no broadly-recommended treatment for jumping oak gall. With a small tree, you could spray insecticide on the tree, but I don t know that it could penetrate the gall to get to the larvae, he said. With a big tree, it s just not practical

3 to try to spray all the leaves. Either way, the tree is typically going to be just fine. The other syndrome currently making an appearance in oak trees in the state is oak anthracnose, a fungal infection that thrives during cool, wet springs such as the one much of Arkansas has enjoyed the past few months. Fungi love moist environments, so in a cool, wet spring, we get all kinds of fungal problems showing up, and oak anthracnose is one of them Barry said. It infects the leaves it can kill the leaves, it can defoliate the tree if it gets to be a serious problem, but it normally only does that once in a summer. So although it can set the growth of a tree back a little bit, it s very rare that it kills a tree. One of the primary recommendations for controlling oak anthracnose is to gather fallen leaves and twigs in the fall and burn them, Barry said. The fungus overwinters in the leaf litter, and spores later splashes up onto the live leaves of low-hanging branches during the rains of the following spring. I am not sure if this will be as big of a problem this year but if you notice white oak trees looking poor this spring it is likely a result of these two common problems. Alion Herbicide Cleared for Use in Blueberry and Caneberry by Wayne Mitchem Alion herbicide contains the active ingredient indaziflam which was originally introduced into the market place as a preemergence herbicide for use in citrus, pome, and stone fruit plantings. The uses of Alion have since expanded and most recently a supplemental label for use in blueberry and caneberry plantings was approved. The blueberry and caneberry supplemental label can be found at and the user must have a copy on hand to legally use the product in these crops. Alion can be used in blueberry plantings established one year or longer while caneberry plantings have to be established three years or more. The label restricts its use to allow a dormant application from late fall thru winter prior to bud swell. If more than one application is applied there must be at least 90 days between applications. The use rate ranges from 3.5 or 5 fl. oz. per acre per application (with a maximum of 7 or 10 fl. oz per acre on an annual basis). Alion rates are variable due to differences in soil organic matter. The higher rate is to be used on soils having more than 1% organic matter while the lower rate is allowable on soils containing less than 1% organic matter. Alion cannot be used in sand soils or soils with a greater than 20% gravel content. Long term residual control of numerous annual broadleaf and grass weeds is the norm for Alion. If the dormant period is long enough to allow two applications to be made 90 days apart you can expect residual control of susceptible weeds to persist for 12 weeks or

4 longer after the last application. Unlike some other preemergence herbicides, Alion provides no postemergence activity and therefore will not aid non-selective postemergence herbicides in the management of difficult to control species. Poisonous Hemlock Spray Demo Below is a picture of this invasive plant that seems to be increasing its area throughout the county. Now is an important time to control this noxious weed before it gains anymore ground. We have a few demo plots around the county to test the effectiveness of various herbicides. The best treatment appears to be GrazonNext at 2oz./gal as a spot spray. If you do not have your Private Applicators License then PastureGard at 1oz./gal worked well. Roundup was also used with good control but this killed everything including grasses so would not be appealing in many cases such as roadsides. 2,4 D showed the least amount of effect.

5 The below picture was taken on April 1 st, 2 weeks after application. The below picture was taken on April 15 th, 4 weeks after application. As always please contact me if there is anything I can do to help you.

Frank A. Hale, Ph.D. Professor Entomology and Plant Pathology and David L. Cook Extension Agent II, Davidson County

Frank A. Hale, Ph.D. Professor Entomology and Plant Pathology and David L. Cook Extension Agent II, Davidson County Multipurpose Fruit Spray These are mixtures containing a fungicide (captan) and either