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Fitting June into the month of May is a different way of thinking for those of us who love the yard and garden. It’s been tough waiting for May 10, the usual frost free date, before setting out annual plants and planting the garden. Maybe history will record a change to this average date as the climate warms.

I was comparing the general types of questions called into the Extension Office today with those of a year ago. It’s not surprising to note that even “Backyard Farmer” program staff are answering questions a month earlier than usual. “A month earlier” seems to be the phase most of us are resigned to think when talking plant science issues in 2012. Let’s discuss just a few of these issues that often are not seen in print.

Maple bladder gall has reappeared. Maple leaves frequently develop growths or swellings known as galls. These are caused by microscopic mites. The mite overwinters under bark scales of the maple tree trunk. Bladder-gall mites become active in the spring and enter leaves as soon as new leaves expand. As they feed, the leaf is stimulated and develops a globular, wart like gall on the upper side of the leaf. These are usually rose or red in color, turning nearly black later in the season. The mite is not considered of economic importance, though maple leaves with the mites’ activity are unsightly.

Rhubarb ascochyta blight causes leaf spots on leaves but does not infect the rhubarb stem. Leaf spots begin as small greenish-yellow spots, less than one-half inch in diameter on the upper leaf surfaces. Leaf spots eventually develop white centers, then turn brown and die out. Remove infected leaves and continue to harvest stalks for eating.

Peach tree borers are showing up in plums. The borer also attacks peach, cherry, apricot and other stone fruits. Branches die back. Trees affected with the borer develop a gummy, often sawdust filled mass on the tree trunk. P each tree borer is difficult to control. Insecticides labeled for use on fruit trees are applied during egg laying, usually in June and early August.

Two spotted spider mites are another damaging pest to watch. With the weather pattern of current, let this be an alert for damage usually seen on ornaments, evergreens and vegetables. Populations can explode rapidly and early control will be needed to prevent damage. Severe damage gives evergreens a dull, grayish appearance as the mites suck the sap from the needles. A still hosing of water to the tree is an economical way of reducing numbers of spider mites or insecticides are available. Spider mites can kill big or little trees.

Cedar-Apple rust appears as bright orange, jello-like galls on cedar trees and other junipers. These evergreens are seldom harmed by this disease. The galls release spores that infect apple and crabapple leaves, causing yellow and orange leaf spots, leaf yellowing and defoliation. While severe defoliation can occur, few trees will die unless severe defoliation occurs year after year. Fungicides applied now will prevent new infections.

Numerous lawn questions keep surfacing. Several are environmental, some are mechanical. If lawns are left to grow tall and, when mowed, more than 1/3 of the shoot is removed, the grass will turn yellow, possibly brown, until it can send up other grass stems. Grass will also sunburn. Most grasses will re-grow within a month. Questions concerning lawns also include mower fuel spills, fertilizer application processes that burn the grass with too strong an application, Ascochyta tip blight, and competition with annual grassy weeds. The University of Nebraska has an excellent reference piece for lawn management entitled “Kentucky bluegrass calendar” (also available for tall fescue, zoysiagrass or buffalo grass).

Winter die-back continues to become visible, including the delayed damage from the early heavy snow that weakened branch structure. Broken limbs need to be pruned correctly and carefully. Remove broken branches where they attach to the trunk or another strong branch. When cutting off a limb, leave the branch collar, but not a stub, at the cutting site. Pruning can begin again in June through fall. Spring blooming shrubs are best cut after blooming has occurred to allow sufficient time for new growth to occur for blooming again the following year.

Remember the easy way to find answers to horticulture questions with University of Nebraska resources. Simply type in the problem to your search engine, such as “pruning shrubs/unl.edu.” and a wealth of information appears. I suggest your best help will come from a Midwest Land-grant University such as the University of NE, Colorado State University, Iowa State University, Kansas State University, etc.

 

 

About the author: Don Siffring

Don Siffring is a 6 year Master Gardener with the University of Nebraska Extension in Adams County. He is a professor emeritus with the University of NE, Institute of Agriculture. Don works part-time as a Horticulture Aide with UNL Extension in Adams County. Don and his wife, Bev, retired to the Hastings Community in in 2003 to be closer to their married daughter and husband, Christi and Brian Berns of Bladen.