Blog Post

Pickleworms?

By Caleb J Malcom, ’23 • May 20, 2023

In 2023 I joined the ranks of the Norfolk Master Gardeners. Now, I’m no stranger to answering plant questions of all kinds. It’s been a lifelong passion. A week does not go by where my phone or email isn’t being hit with a plant or insect question from a friend or family member somewhere in the world. I always enjoy answering the question and if it’s not something, I know, I love hunting down the answer. So I was happy to volunteer at the information table at the spring plant sale at the Hermitage. I was able to help with many curiosities and anxieties but then came the question of the pickleworm.


 Pickleworm? I had never heard of such a thing before. Comical images of pickle shaped worms danced through my head. I had to know more. What did it look like? What was it eating? And, of course, I'm sorry I didn’t know much about this pest but I knew I soon would. The lady with questions about pickleworms told me each year they ravaged her cucumbers. Cucumbers you say? I must know more about these pesky creatures. And VCE is one of several Extension websites with informative material, Pickleworm (vt.edu)


The pickleworm (Diaphania nitidalis), sometimes pickle worm, is a rather lovely night flying moth species (lovely until it’s in your garden that is). This interesting little creature is actually native to tropical areas of the Americas but does overwinter in southern Florida and southern Texas. They then spread out throughout North America and are a pest to the cucurbits family ranging from Florida, to Canada, and west to Oklahoma and the rest of the Great Plains. They seem to have an affinity for squashes, watermelons, and cantaloupes as well. I’ll admit I groaned at this, “Oh no, another pest to squash!”

So what do they do? The adult female lays her eggs on the fruiting bodies or the plants of cucurbits. Sometimes even on the flowers. She can lay 300 to 400 eggs in her life. These tiny eggs will hatch in approximately 4 days. The larva hatches then greedily begins to chow down on whatever it is on. They will also bore into the fruits that we so desperately want for ourselves. These tiny green little larvae will even eat the flowers of our beloved plants. Now these little larvae go through five different instars. The total process takes 14 days before it turns into a pupa. In its pupa stage it likes to wrap up in dead leaf litter. Pupation lasts 8 to 9 days and then a new adult emerges into the world.

Okay wonderful. Another insect that loves our squash and cucumbers. But what do I do about it? Well there are some predators that will munch on them. It seems Ground Beetles (Calosoma and Harpalus) like to eat them. As well as Soldier beetles (Chauliognathus pennsylvanicus) have been seen predating them. A handful of parasitoids may also aid you in the fight against the pickleworm they include but may not be limited to Apanteles sp., Hypomicrogaster diaphaniae, Pristomerus spinator, Casinaria infesta, Temelucha sp. (both Ichneumonidae). So creating safe environments for these predators just may help in the battle against the pickleworm. But all of these wonderful predators do not show a great result in keeping the pickleworm at bay. So what are some other options we have?

 

What about insecticides? Due to the high importance of pollinators to cucurbit production, insecticides are not generally recommended. Personally I try to avoid insecticides in general. The application of insecticides that kill these hungry little larva has the potential of killing off the bees that are so important to giving us the delicious foods we hope for each season. It is suggested that if you use an insecticide that you use one with a low residual activity.


Nematodes might also be our friends in the battle against pickleworms. Steinernema carpocapsae is a nematode that helps with pickleworms on our squash. It is mentioned that it may not help in pickleworm infestations on cucumbers due to the smaller flowers. Further research may be needed to be done on the topic of pickleworms and nematodes.


Another method of prevention are screens and row covers. The pickleworm moth is a night flying moth so covering your plants at night and then removing them in the morning may just be the trick in saving your plants. This will allow our wonderful pollinators to get to them in the daytime and keep those eggs off our plants in the midnight hours.


There are also some squash varieties resistant to them, but I could not find any cucumber, watermelon, or cantaloupe varieties that are resistant to them. Maybe cucumbers will have varieties of those that are resistant to them. The squash varieties include Butternut 23, Summer Crookneck, Early Prolific Straightneck and Early Yellow Summer Crookneck.


Planting the crops earlier in the year may be another option for some gardeners. This will allow the gardener to pick some of the delicious crop before the invading pickleworm moth arrives in the night. Maybe combining row covers at night will get you a lot more?


Then there is something I have been told my whole life about growing vegetables. Sometimes we just have to accept that nature does what it will. We harvest what we can and enjoy that harvest. Then we appreciate, even in our frustrations, the amazement of such creatures. Hopefully your battles against pickleworms are fruitful.

           

 

References:

https://edis.ifas.ufl.edu/publication/IN321

https://extension.tennessee.edu/publications/Documents/W206.pdf

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