Poor pollination

About

Squash, cucumbers and melons need bees to carry pollen from male to female flowers, and corn needs wind to carry pollen from tassels to silks. When that fails, fruit stays small and misshapen or ears have gaps.

Also called poor pollination, pollination problems, incomplete pollination, misshapen cucumbers, poor ear fill, poorly filled ears

How to recognize it

Symptoms

Tiny fruit behind a female flower stops growing and drops off with the bloom or a few days later. Fruit that does grow may be stubby, curved or pinched at one end. Corn ears have missing kernels or poorly filled tips.

Often confused with

Heat stress drops flowers before any fruit forms. Squash opens male flowers first, up to a week before the females, and those male flowers fall off normally.

Worse when

Cool, rainy or cloudy weather when bees stay home, insecticide sprays during bloom, very hot weather that kills pollen, too few pollinators, and corn planted in one long row instead of a block or stressed by drought.

How it spreads

It does not spread.

When

Bloom time, early to midsummer.

What to do, gentlest first

This is not an infection, so sprays for diseases won't help. Fix the cause below.

1. Protect and invite pollinators Prevent

   Grow flowers nearby that feed wild bees, and don't spray insecticides on blooming vine crops. Squash and cucumber flowers open for only about one day.

   If a spray is needed during bloom, UMD limits it to insecticidal soap or horticultural oil, and Penn State advises spraying when flowers are closed.

2. Plant corn in a block Prevent

   Plant 3 or 4 short rows side by side instead of one long row, and keep corn watered so pollination isn't stressed.

3. Hand-pollinate By hand

   For squash, find a male flower (thin stem) and a female flower (tiny squash at the base), and move pollen from the male's center to the female's with a small paintbrush or cotton swab. For corn, shake or dab pollen from the tassels onto the silks.

   Each corn silk leads to one kernel, so dust the silks thoroughly.

4. Pick off failed fruit By hand

   Remove shriveled or badly misshapen fruit so the plant puts its energy into new, well-pollinated ones.

   Parthenocarpic (seedless greenhouse) cucumbers need no pollination, and if bees do pollinate them the fruit can become misshapen.

Plants it affects

Cantaloupe (muskmelon), Cucumber, Sweet corn, Watermelon, Winter squash and pumpkin, Zucchini and summer squash