Extension News

Ask the ISU Experts

Sapsucker damage

Note to media editors:

Got gardening questions? Contact the Hortline at (515) 294-3108 (M-F; 10-12 & 1-4:30) or send an e-mail to hortline@iastate.edu. For more gardening information visit us at Yard and Garden Online at www.yardandgarden.extension.iastate.edu


What is the correct way to plant sweet corn in the home garden? 


Sweet corn performs best in fertile, well-drained soils in full sun. Standard sweet corn (su) varieties may be planted in late April in central Iowa. It’s generally recommended that sugar enhanced (se) varieties be planted one week later than standard sweet corn varieties. The seeds of shrunken-2 or supersweet (sh2) varieties germinate poorly when soil temperatures are below 65 degrees F. As a result, shrunken-2 varieties should not be planted until mid-May in central Iowa. For a continuous supply of sweet corn, plant early, mid-season, and late varieties or plant every two or three weeks. The last practical planting date for early varieties is July 1. 


Sow seeds at a depth of 1 inch in heavy soils. In light sandy soils, the planting depth may be 2 inches. Space the seeds 8 to 12 inches apart in rows 2 1/2 to 3 feet apart. Sweet corn may also be planted in "hills.” Sow 4 to 5 seeds per hill with approximately 3 inches between seeds. Hills should be spaced 2 1/2 feet apart with 2 1/2 to 3 feet between rows. 


Sweet corn is wind pollinated. To ensure good pollination and ear development, plant several short rows or blocks rather than 1 or 2 long rows. Inadequate pollination results in poorly filled ears. 


Since different types of corn can cross-pollinate and contaminate one another, they should be isolated from each other. All sweet corn types should be isolated from field corn, popcorn, and ornamental corn.  Shrunken-2 varieties must also be isolated from sugar-enhanced and standard sweet corn varieties. Cross-pollination between the sh2 and se or su varieties will destroy the quality of both. It is not essential to isolate sugar-enhanced varieties from standard sweet corn. 


Isolation can be achieved by planting the different types at least 250 feet from one another and by avoiding prevailing winds. Another method is to stagger planting dates or to select varieties that mature at different times. A minimum of 14 days should separate the tasseling times of the different types. 


There are several bands of holes around the trunk of my pine tree.  Is the tree infested with borers? 


The holes were likely created by sapsuckers. Sapsuckers, members of the woodpecker family, damage trees by drilling holes in the trunk or large branches. Sapsucker damage is very distinctive. They drill uniform, 1/4 inch holes in distinct rows.  (In contrast, the holes created by insects are random.)


Sap that flows from these wounds is eaten by the sapsuckers. They also feed on insects, such as ants, beetles, and wasps, that are attracted to the sap. The damage caused by sapsuckers is usually not serious. However, sapsuckers can destroy trees if they drill several rows of holes around the trunk within a small area.  The bands of holes effectively girdle the tree trunk.


To discourage additional damage to trees, home gardeners can wrap a piece of burlap around the damaged areas.  Another option would be to spread a sticky substance, such as Tanglefoot, around the affected area. Trees most commonly attacked by sapsuckers include apple, crabapple, sugar maple, mountain ash, birch and pine. 



How can I control weeds in my raspberries? 


Cultivation and mulches are the most practical weed control measures for home gardeners. Cultivate the raspberry plantings frequently during spring and summer. To prevent injury to the roots of the raspberry plants, don’t cultivate deeper than 2 to 3 inches. 


Mulches help to control weeds and conserve soil moisture.  Possible mulching materials include straw, shredded leaves, lawn clippings, crushed corncobs, sawdust and wood chips. The depth of the mulch needed depends upon the material. The depth ranges from 3 to 4 inches for fine materials, such as sawdust, to 8 to 10 inches for straw. Since mulches gradually decompose, apply additional material each year. Avoid mulching poorly drained soils to discourage root diseases. 



Contacts :

Richard Jauron, Horticulture, (515) 294-1871, rjauron@iastate.edu

Jean McGuire, Continuing Education and Communication Services, (515) 294-7033, jmcguire@iastate.edu

There are  two high resolution photos for use with this week's column:

Sapsucker on Scots pine, 397 KB

Sapsucker on Austrian Pine, 1.72 MB