A Few Of This Seasons Squash and Cucumber Problems

by Yvette Henson
San Miguel Basin, CSU Extension


Summer squash and cucumbers are generally two of the easiest and most productive veggies to grow in Colorado gardens, provided they get enough warmth.  Winter squash can be a bit more difficult because they need a long season to mature fruit.  Even though they are easy to grow, given the right conditions, they are not without problems.  In the last two weeks, myself, my Mom and my friend Pam, have experienced thrips on cucumbers, blossom end rot on summer squash and squash bugs on winter squash. 
    

Thrips are very small, slender insects with feathery wings.  Western flower thrips feed on hundreds of species in our area, including cucurbits (name for all squash, pumpkins, gourds, cucumbers, melons).  They have piercing, sucking mouthparts and feed on buds, flowers and leaves, weakening plants and deforming fruits.  They can transmit virus diseases.  They can also fill a beneficial role and feed on spider mites but that isn’t comforting to me right now-- It's my 2 precious cucumber plants that are infested.  

Thrips on cucumber flower

Thrips feeding damage on cucumber leaf

Thrips thrive in hot, dry conditions—just what I have been experiencing so far this summer.  Cultural controls are to spray the foliage when watering to create a more humid environment and to remove weeds in the area that may be alternate hosts for thrips.   Also, don’t apply too much nitrogen fertilizer, which encourages thrips population explosions.  (Ooops!  I was just trying to get my plants to grow fast so I could get fruit in my short-season!)  

Other control options for thrips, including organic and inorganic pesticides, can be found in this publication: http://ipm.ucanr.edu/PMG/r116302111.html  Research any and all insecticides before using to be sure that they won’t kill non-target beneficial insects and remember to always follow the label!  


Tomatoes aren’t the only ‘vegetable’ to get blossom end rot.  My Mom ended up with blossom end rot of her summer squash (see photo).  The cause of blossom end rot is insufficient calcium uptake by the plant due to inconsistent moisture levels in the soil.  This is not the same as a calcium deficiency in the soil.  It is more common on the first fruits of the season.  On rare occasions, it can be caused by insufficient pollination. 

 

Blossom end rot on summer squash

To prevent blossom end rot, water regularly and evenly to about 6-8”deep – don’t allow soil to dry out too much between watering but don’t allow soil to be waterlogged either.  Something else to try that seems to have worked for me is to apply a liquid Cal-mag fertilizer occasionally.  See this publication for more information on blossom end rot on veggies: https://www.canr.msu.edu/news/blossom_end_rot_causes_and_cures_in_garden_vegetables

I live in the mountains so my cucurbits are just starting to grow and bloom.  My friend Pam lives in Olathe, a much warmer climate, and her warm-season veggies are starting to produce.  She hasn’t been home much because of work, so she asked me if I wanted to harvest some of her garden.  Why, of course!  Thank you, Pam!  When I wasgleaning from her garden, I noticed that one of her squash plants was wilted.  At first, I thought it was squash vine borers, but I couldn’t find any larvae or frass inside the base of the wilted vine.  On second inspection, I found 4 dreaded squash bugs!

male and female squash bug (I interrupted their mating to take this photo)

2 of 5 winter squash plants showing wilt symptoms from squash bug feeding

Squash bugs can be found most commonly on winter squash and pumpkins but they sometimes feed on summer squash, gourds and melons.  They lacerate plant tissue when they feed, causing rapid wilt and eventual death of the plant.  One thing that Pam could have done to reduce squash bugs was not to use the black plastic mulch as weed control.  Mulch gives the squash bugs more places to hide.  She decided to use an insecticide she already had that was listed as a control in this fact sheet:  https://extension.colostate.edu/topic-areas/insects/squash-bug-management-in-home-gardens-5-609/  The sad thing is she will most likely lose most of the plants that are already infested.  The original affected plant I saw progressed to 5 affected plants in just a week!


More information about other problems one might experience when growing other cucurbits, not jsut squash and cucumbers can be found below.


In instances where there are not enough pollinators or plants are grown under season extension covers there may not be pollination and fruit set file:///C:/Users/YvetteH/Downloads/FruitSetProblems.pdf


Cucurbits can also be attacked by cucumber beetles, aphids, spider mites and powdery mildew and more!  https://hgic.clemson.edu/factsheet/cucumber-squash-melon-other-cucurbit-insect-pests/