In the Garden:
Southern California Coastal & Inland Valleys
June, 2007
Regional Report

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Multi-stalked corn provides more photosynthesis for healthy plant growth.

Troubleshooting Corn Problems

Despite the abundance of sweet corn in grocery stores and farmer's markets, some of us choose to grow our own because -- like so many other vegetables we grow -- we can choose the variety, and we have complete control over what amendments we incorporate and what techniques we employ. Consequently, we also have to deal with the vagaries of growing our own. Here are some of the problems we may see, and things we can do to result in a successful harvest.

Problem: Plants grow slowly early in the season; the weather is still too cool.
Solution: Cover plants with hotcaps to retain heat, or wait for warmer weather to sow the seed.

Problem: Leaves roll upwards. Plant needs immediate irrigation.
Solution: Irrigate more deeply and frequently and use organic mulches to retain moisture.

Problem: Leaves develop green and yellow striping at their base, indicating zinc deficiency. This occurs more frequently on wet heavy soils in the early spring and may be due to excessive phosphorous.
Solution: Incorporate manure.

Problem: Leaves appear streaked. Indicates potash deficiency, especially if the plants are grown on very light soil that allows nutrients to leach.
Solution: Incorporate manure, seaweed, wood ashes, greensand, granite dust, non-woody plant residues, manure, or compost.

Problem: Yellow striping on leaves. Indicates manganese deficiency, especially on soils with a pH above 6.7.
Solution: Incorporate manure.

Problem: Reddish streaks on leaves. Indicates phosphorus deficiency.
Solution: Sidedress with a complete fertilizer.

Problem: Holes in leaves.
Solution: Various insects will chew holes in leaves. Ignore the damage unless it is severe, or handpick and destroy the insects. The loss of a small amount of leaf will not reduce the yield.

Problem: Stunted plants with speckled leaves and ears that are filled but may have missing kernels indicate sugar cane mosaic.
Solution: Plant resistant varieties.

Problem: Stalks fall over after a moderate wind, especially after rain or irrigation. Indicates poor root anchoring.
Solution: Corn is naturally shallow-rooted and benefits from having soil hilled up around the stalks. Add more soil every two weeks until tasseling begins. This extra soil also serves as a mulch to retain moisture.

Problem: Bright green to purplish-brown worms present on the silks or eating their way down through the kernels at the tip of the ears. Brown, sawdust-like material close to the damaged area. These indicate corn earworms.
Solution: Plant resistant varieties as early in the season as possible to avoid higher populations later in the summer. Apply Bt, lime, or mineral oil to silks just inside the tip of each ear as soon as the silks have begun to turn brown. Applying these sooner will interfere with pollination and result in poorly-filled ears. In hot, dry weather, however, the oil may spoil the ears. Encourage lacewings, toads, spiders, and ladybird beetles. Break off and destroy the damaged portions. Destroy the ears or portions which have been damaged to prevent the worm from maturing.

Problem: Small ears that are poorly filled with incompletely developed or shriveled kernels -- but with no insect damage. Poor pollination, insufficient irrigation (especially from silking through harvest), hot weather or high winds from two to three weeks before harvest, or planting a variety that is not adapted to the area.
Solution: Plant corn at least four rows wide and long to accommodate pollination by breeze. Water and fertilize the corn well, as it is a heavy drinker and feeder. Grow varieties that are appropriate to your area.

Problem: Kernels that are tough and doughy, somewhat shrunken, and taste starchy. Corn is overmature or not watered enough.
Solution: Irrigate corn deeply for the approximately three weeks from when the silks first appear until they dry up and the kernels are full of milky juice. If the corn is not harvested during this milk stage, its sugar turns into starch.

Problem: Large gnarled galls that are greyish-white to black indicates corn smut infestation.
Solution: This disease thrives in hot, dry weather. Late-maturing corn is more susceptible. Plant disease-resistant seeds early in the season on a three-year rotation of crops. Remove and destroy affected plants immediately to keep the powdery spores from spreading. Do not compost. On the other hand, this fungus, called huitlacoche, is prized in Southwest cuisine, and corn is purposely inoculated to result in a plentiful harvest.


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