Tuesday, May 30, 2017

Summer Garden Pests: Cabbage Worms, Corn Earworms, & Squash Bugs

Cabbage worm damage

Warm summer days mean you need to be on the look out for summer garden pest. People seem to approach pest control with two attitudes:  the chemical warfare approach or the homemade remedy approach.  What is lacking in both of these approaches is an understanding of insects life cycles and insect feeding habits and how the approach kills insects and how the pesticide is intended to manage your problem

. You have to know your enemy to be successful. Different sprays whether synthetic, organic, or homemade are effective at certain stages of the insect's life cycle and their mode of killing matters.  Does it have to be ingested or does the insect have to have physical contact with the pesticide?  Also important to consider is does it leave toxic residue?  And finally is it a broad spectrum spray killing beneficial and predatory insects as well as the pest or is it safe for beneficial insects?  Some homemade remedies kill pollinators, lady beetles, and predatory insects as well as the pest.

While I don't agree with with chemical warfare especially for the backyard and small scale grower I also do not think a homemade remedy will be any more effective you don't understand the feeding methods, killing mode, and the stage at which each is most effective.  With the increase in organic food there has been an increase in the development of organic pest management methods.  Armed with only a couple of controls and a little knowledge you can literally take care of most pests in your garden. Organic gardening is science based.  We work with the knowledge we have of plant biology to manage both pests and disease.

Planting at the right time is an important IPM strategy.  Brussel sprouts do best and have fewer pest issues if planted as a fall crop.

Integrated Pest Management or IPM is the currant term used to manage pests.  Basically it is a fancy way of saying that you will prevent and control pests by various methods.  Overall it means you are practicing good gardening habits, monitoring for pests, and only treating when necessary. Sprays whether organic or synthetic are a last resort in most cases.

Organic IPM's involve first and most importantly building a healthy soil including both good soil structure and a healthy soil food web.  This is done by incorporating organic matter into the soil. Organic matter provides the food for healthy microbes.The microbes in turn create a bio slime that binds soil particles together allowing for oxygen and water to penetrate and root paths to develop. 

Organic fertilizers such as bone meal and blood meal actually feed the microbe population and in turn plants excrete exudates that attract just the right microbes to the root zone.  These microbes become the fertilizer for your plant.  Bacteria are mini fertilizer bags and fungi are mineral miners that bring nutrients to the root zone of the plant.

Mulching around plants is part of a good IPM plan.

Cultural Methods:  Minimal tilling to maintain soil structure, mulching, good sanitation practices, crop rotation, companion planting, proper plant spacing, planting at the proper times, proper fertilizing, and water.  Many pests we inviting into our garden because of our poor garden habits.  For example water stressed plants are vulnerable to attack by pests.

Biological Methods:  planting nectar producing flowers and herbs among your garden crops provides shelter and food for pollinators and predatory insects such as lace wings, lady beetles, predatory wasps, beetles, and pirate bugs etc. Providing a water source and not using any spray synthetic or organic that kills the good guys.

Releasing beneficial insects and using predatory nematodes is an important biological control.

Planting resistant varieties is also a good practice.

Monitoring for pests:  Spend a little time in the garden each day.  Check the underside of leaves for eggs and larvae.  Look for sucking damage and chewing damage.  Sticky traps are good for monitoring what insects are in your garden.

Strategies for controlling pests:  handpicking pests off, spraying off with water (aphids), crushing eggs, covering with a light weight row cover, trapping, and using soft organic sprays that selectively kill the pests with little or no damage to the "good bug" population are all apart of organic IPM.

So lets look at a few summer garden pests and see how you would implement an IPM.

Cabbage worm on underside of cauliflower.

Cabbage Worms

That pretty little white butterfly you see flitting about your garden early spring is searching for your cabbage, broccoli, kale, cauliflower, and brussel sprouts.  It lays it's eggs on the underside of leaves and the larvae, a little green caterpillar, has a voracious appetite and is responsible for all the holes in your leaves.

There are 3  common caterpillars active right now: the imported cabbageworm, cabbage lopper, and diamondback moth.  

The imported cabbageworm is the larvae of the white butterfly you see so often enjoying your garden.  It is a lime green to dull green caterpillar feeding on the underside of leaves.  

The cabbage lopper adult is a brown moth.  The larvae is a light green with white stripes down it's back.  It moves like an inchworm.

The diamondback moth larvae is a light green caterpillar with two hind prolegs that stick out the back.  This worm only grows 1/2 inch long.

All three green demons chew holes in the leaves of the Brassica family and leave frass (excrement) on your produce.
A healthy cabbage forming a head with no pest damage.

IPM Strategy:

Monitor daily.  Look for holes and check the underside of leaves for the worm.  Hand pick them off which is all you need to do if you have a small garden.  Cover with row covers in early spring to prevent egg laying.  Kaolin Clay (Surround) is what it says, a clay that is sprayed on to deter feeding  Spinosad is a fermented bacteria product that is ideally designed to kill caterpillars.  It is safe for beneficials but until dry can kill bees.  Normally bees are not hovering around cabbage but to be safe spray early morning or evening when bees aren't flying.  Spinosad leaves no toxic residue and can be repeated if needed every 10 days. Neem oil is also effect and safe for all beneficials. It must be ingested to kill an insect.  Neither of these sprays instantly kill they disrupt feeding, molting, and disrupt the nervous system so you see results in a day or two.  

An example of interplanting cauliflower with onions and celery.

Cabbage Aphids

These pesky insects live in colonies and are easy to dentify. They have a white waxy coat.  The female gives birth to many live offspring both winged and wingless.  They are fast growing colonies. They like cabbage, kale, broccoli, cauliflower, and Brussels sprouts.

Feeding and Damage

Yellowing foilage, stunted growth, and cupping leaves are caused by the aphids feeding.  They suck the juices of the leaves.  

Monitor daily around the cauliflower leaf wrappers for cabbage aphids.

IPM Strategy:

Look for the start of aphid colonies on the youngest, highest, and innermost leaves of plants.  You need to check the flowing parts of broccoli and cauliflower and pull back the wrapper leaves of cabbage.

It is important to plant those crops of the cabbage family in early spring.  Much of your harvesting can be done before aphids appear.  Monitor daily and spray off with a stream of water colonies that start.  If it gets out of control you can spray with Neem oil or pyrethrin.  Insecticidal soap which can be homemade or purchased works on aphids but is photo-toxic if applied in high temperatures. Be cautious in using  insecticide soap.  Test it first.

 Interplanting members of the cabbage family with onions and among other crops seems to also help.

Squash Bugs

Squash bugs are active now laying eggs with nymphs hataching 10-14 days later.  A nymph is juvenille squash bug.  It is a small gray black bug that does not resemble the adult.  Squash bugs overwinter as adults and in June find your plants in the curcurbit family and lay a cluster of copper colored eggs on the underside of leaves between the veins. They continue to mate and lay eggs through September. Eggs and nymphs are easy to manage.  The adults are more difficult to manage.

Feeding and Damage

The nymphs feed on plant juices causing yellow speckling and browning.  The adults feed on the vines damaging the xylem which allows for water transport to the leaves.  This causes wilting of individual leaves or an entire section of the plant.  

IPM Strategy

Monitoring when your plants are young and producing flowers is critical.  Check the underside of leaves between the V of the veins.  Squish egg clusters or cut them out. Insecticides can be used to kill nymphs. Handpick any adults or nymphs daily when inspecting your plants.  I use a combination of sprays when I see adults or nymphs.  In one sprayer I put neem oil, pyrethrin (pyola), and kaolin clay.  The pyrthrin kills on contact and is the only thing that seems to work on the adults.  The neem works on the nymphs and is systemic meaning it is taken up by the leaves.  The kaolin clay is a feeding deterrent.  

After and during bloom spray only in early morning or late evening before pollinators are out.  This can be repeated every 5 days.  You need to keep monitoring for eggs.  Another very successful option is to use ducks.  Once the plants are mature enough ducks love to eat squash bugs.  When picking them off plants I put them in a bucket and feed them to the ducks. 

This might sound labor intensive so if you truly do not have time do not plant squash.  Allowing squash bugs to take over ensures that the following season your problem will be worse. 

You might be thinking why not use a synthetic spray such as Sevin?  The people who use Sevin are the people who most often ask me how to get rid of squash bugs. Sevin is a broad spectrum insecticide that really has no place in the backyard garden. It is not more effective than the methods I suggest and is NOT a one time squash bug killer. There is no way to exterminate all pests that's why it is call a Integrated Pest Management system requiring management on the part of the gardener.

Corn Earworms

The corn earworm (Helicoverpa zea) is one of the most destructive insect pests attacking corn.  The adults are a brownish grey moth that can travel long distances.

Damage usually begins in the corn’s silk, where the moth deposits its eggs. The caterpillars (larvae) follow the silk down to the ear, eating as they go. Extensive damage is often found at the ear’s tips, where the worms devour kernels and leave their excrement. 

The larvae can often destroy the silks before pollination is complete. The result is deformed ears often then susceptible to mold and disease. Worm damage is usually confined to the tip of corn ears and can easily be cut away. 

Each year, massive amounts of pesticides are sprayed on commercial corn fields in attempts to kill larvae. Genetically engineered corn, each kernel producing its own pesticide, was developed with corn earworms in mind. Fortunately corn earworms a relatively easy pest  for the backyard grower to control.

No damage from corn earworms.  This is Jubilee sweet corn.

IPM Stategy

In the fall, tilling will expose the pupae or chickens and ducks can be turned loose to dig for pupae. Corn which requires block or a large planting for complete pollination is one crop I plant in a field in deep wide rows.  I rotate it every year. If I till I do so in early spring.  In the fall the chickens and ducks clean up the remaining pests. 

Im not sure if this is actually beneficial but I have a bug zapper that is near my orchard and corn field.

Begin spraying Spinosad (Captain Jack's Dead Bug Drew) when the silks are developed and spray until they dry every 10 days.  Bt or Neem will also work but I prepfer Spinosad when dealing with caterpillars.

If you have only a small patch of corn, then you can add  vegetable or mineral oil to the ears tips to suffocate feeding larvae.  To make that more effective add a little Neem Oil. This is very labor intensive and not as effective as using Spinosad.

Dried silks mean you no longer can treat for corn earworms.

Knowledge truly empowers the gardener to come out conqueror in battling summer pests.  Don't give up!  Enjoying organic fresh produce you grow yourself is so rewarding and worthwhile. I did not include many pictures of the pests because I don't have very many pictures  Also I wanted to show you that organic methods work very successfully for the backyard grower.  Your garden will feed your family and not your frustrations of summer pests.  


  1. Great post! I've had trouble with squash bugs and cabbage worms. I had no idea that the pretty white butterflies were the parents though. I'll have to watch that more closely. As for squash bugs, I plant my squash plants pretty early and and by the time the bugs come out, my plants are finished producing squash anyway. I'm intrigued by the neem oil though, I've never tried it. Thanks for the tips!

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