FLORIDA – Q. My cucumber and squash plants are not setting fruit even though the plants appear healthy. I’m not seeing many bees. Can this be part of my problem?
A. More than likely this is the result of incomplete pollination. Cucumber and squash are in the same plant family (Cucurbitaceae or Cucurbit for short).
Plants in the cucurbit family have separate male and female flowers occurring on the same plant. The male flowers produce pollen that has to be moved, usually by bees and other pollinators, to the female flowers.
Both male and female flowers are yellow. The female flower will be attached to the plant by what looks like an immature cucumber on cucumber plants or an immature squash on squash plants. The male flower is attached to the plant by a thin, short greenish stem.
A common reason for incomplete pollination is when there is an insufficient movement of pollen from the male flowers to the female flowers.
In most cases, this means that there were not enough bee visits to transfer enough pollen for pollination to occur and subsequently fertilization to allow the fruit (cucumber, squash) to develop.
This lack of pollination results in either the fruit aborting (no fruit at all) or only developing partially around the seeds that did become fertilized, producing small malformed fruit.
Researchers have found that it takes at least eight honeybee visits per flower to pollinate cucumbers and/or squash adequately.
In the absence of sufficient bees, you can try hand pollinating. This can be done by transferring pollen from newly opened male flowers using a small brush or cotton swab. Then deposit the pollen on the sigma, which is on a raised area in the middle of the open female cucurbit flower.
This requires knowing how to tell the difference between the male and female flowers.
More detailed information, including pictures, on how to hand pollinate squash is available through this link. https://edis.ifas.ufl.edu/publication/HS398.
To have a printed copy of this UF/IFAS Extension publication mailed to you, call the Okaloosa County Extension Office at (850) 689-5850 and request the hand pollination of squash publication and provide your name and mailing address.
Also, be careful with certain insecticides on or near your cucurbit crops such as carbaryl, particularly while the plants are blooming.
Carbaryl and some other insecticides are highly toxic to honeybees and other bees exposed to direct treatment or residues on crops or weeds in bloom. Always follow the label directions and precautions when using any pesticide, including insecticides.
Larry Williams is the Extension horticulture agent with the Okaloosa County Cooperative Extension Service, University of Florida. Contact Larry at 689-5850 or email [email protected].
