NUMBER 1213 |
September 29, 2009 |
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CORN |
SHADE TREES & ORNAMENTALS |
| Stalk Strength Reminder By Paul Vincelli |
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The easiest way to check for lodging potential is to walk through the field and, at about chest height, push the plants about 8-12 inches from vertical. A stalk that bends and fails to spring back is prone to lodging. If 10-15% of the stalks in a field exhibit lodging potential, the field should be scheduled for early harvest.
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| Storing Diplodia Ear Rot-Affected Corn By Paul Vincelli |
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Fortunately, there are no known mycotoxins produced by the strains of the DER fungus found in North America. In addition to several recent Kentucky Pest News articles on this subject, more information on this disease is available in a UK Extension publication available at http://www.ca.uky.edu/agc/pubs/ppa/ppa43/ppa43.pdf. |
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| Bt Corn Refuge Requirement Confusion By Ric Bessin |
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This has become a bit more complicated with the approval of SmartStax corn. The minimum refuge size for SmartStax is different, it is only 5% of total corn acreage (in cotton producing areas it increases to 20%). Where the possible confusion lies is that the refuge size for all other Bt corn technologies stays the same, only the SmartStax will have the reduced refuge size of 5%. The table below outlines the refuge requirements for the various Bt technologies on the market, corn grown in Kentucky would use the corn belt minimum refuge sizes. The reason why there is a reduced refuge with SmartStax is that we use multiple independent toxins to control the key insect pests. This is a new strategy for resistance management that the other Bt technologies don’t have.
There are two other types of Bt corn that are still in the regulatory process with approvals pending. This includes AcreMax and Viptera. These again may have different refuge requirements, particularly the AcreMax. While the reason for planting a refuge is to maintain a population of Bt- susceptible corn borers, growers should still manage those refuges to avoid serious losses. When using a 20 or 5 % (Smartstax only) refuge with Bt corn plantings, growers may consider spraying for corn borers if scouting indicates it is an economic problem. |
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| Flowering Crabapples Blooming Now? By John Hartman |
 Figure 1. Out-of-season blooms of flowering crabapple on leafless branches. 
Figure 2. Flowering crabapple with September fruit and newly appearing flowers. Apple scab, caused by the fungus Venturia inaequalis, was more severe this year than usual. During spring and early summer crabapple trees were exposed to extremely rainy conditions with long periods of leaf wetness which favored scab infection. Scab-infected crabapple leaves turn yellow and drop from the tree within weeks of the onset of disease. Thus, by midsummer, many crabapples were left practically defoliated (Figure 3). The old-fashioned highly susceptible crabapple cultivars such as ‘Almey’, ‘Eleyi’, and ‘Hopa’ were especially affected. Many of the moderately susceptible crabapples were also defoliated.  Figure 3. Mid-summer defoliation of flowering crabapple. Homeowners may want to know why crapples are blooming now, and if this will affect their tree in other ways. It is possible that extensive loss of leaves in mid-season could have been similar to autumn leaf drop and might have caused parts of the tree to become physiologically dormant, similar to winter. Normally, after winter dormancy the tree puts out new blooms. September crabapple blooms and new leaf growth tend to be sparse and scattered throughout the tree (Figures 4 &5), so apparently not all flower buds are opening now. As for spring bloom next year, expect fewer flowers because defoliated trees set fewer flower buds and some buds have already been expended. Depending on when first killing frost occurs, some of the new shoot growth accompanying the fall blooms may not be fully hardened off and could be damaged by cold.  Figure 4. Flowering crabapple tree with scattered blooms in September.  Figure 5. Close-up of fall blooms also showing some new leaves. Crabapple scab normally does not kill crabapples, but annual defoliation could weaken the trees, making them susceptible to other problems. Homeowners can help improve the health of their flowering crabapples by doing the following:
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| By Patricia Lucas | ||||||||||||||||||||||||||||||||||||||||||
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September 3-18
Graphs of insect trap counts for the 2008 season are available on the IPM web site at -http://www.uky.edu/Ag/IPM/ipm.htm. |
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NOTE: Trade names are used to simplify the information presented in this newsletter. No endorsement by the Cooperative Extension Service is intended, nor is criticism implied of similar products that are not named.