Grubs in Compost – Good Or Bad?

Last Updated on March 18, 2022 by Grow with Bovees

If you’ve noticed unsightly grubs crawling in the organic matter, moist food waste, and other material in your compost, there’s no need to break a sweat just yet.

The good news is that the grubs in compost are going to do exactly what you want them to do, that is consume your organic matter, and provide you with nutrient-rich compost. 

What are Grubs? 

Often dubbed as brown June beetle larvae or white grubs, lawn grubs are a bunch of white, C-shaped creatures with brown heads that are notorious for their below-ground construction. 

C-shaped white grubs are the beetle larvae of the Japanese beetle, scarab beetle family, green fruit beetle, black soldier fly, green June beetle or bumble flower beetles (cream-colored grub with a dark brown head capsule), eats rotting fruit and everything from plant material including lawn roots, to organic material in the soil, and decaying organic matter.  

Grubs emerge in the early part of summer, feed on your garden plants, and lay eggs in the soil on your lawn. You can use dish soap for lawn grub control, see our post here. The eggs hatch into beetle larvae later in the summer, after which they begin to eat plant roots, turfgrass, rotting fruit, and vegetables. 

There are several species of grubs, where each slightly varies in appearance, but typically measure between 3/4 to 1-1/2 inches in length with dark brown heads. They curl up into a C-shape whenever disturbed and have relatively long life cycles in a vegetable garden, compost heap and lawn 

Common Grubs Found in Compost Piles 

The most common types of grubs in compost heaps include pepper weevil grubs, white grubs, and vine weevil grubs.

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Pepper Weevil Grubs 

Anthonomus eugenii (scientific name) or pepper weevil grubs are the single biggest enemy of the pepper plant, and identifying them is highly important owing to the difference in the damage they can do to roots of plants and other plant material. 

They measure approximately ⅕ inches when fully mature, and aren’t C-shaped like white grubs, but instead have a dark body that has a brassy luster to it and an oval shape. 

Even though pepper plants are the primary prey of pepper weevil grubs, these pests can also much on nightshade plants. 

Vine Weevil Grubs 

Vine weevil grubs feature cream-colored bodies and brownish-orange heads and hatch into 10 mm long C-shaped creatures. They are inactive during the day and are mostly found between April and early August. 

Vine weevil grubs can attack almost any plant and can be present in your compost mix, compost pile, compost tumbler, compost barrel, compost bins, and compost containers. 

Advantages and Disadvantages of Grubs in Compost

Finding grubs in your compost can be a startling sight, and though they are good for your compost pile, there are also many reasons you may want to get rid of them. 

Advantages of Grubs in Compost Pile

Grubs are one of the few types of adult beetles that do a good job at consuming rotting organic matter. Further, they break down the cellulose in plant material inside their intestinal tracts, which greatly improves the quality of your compost. 

When grubs feed on compost, they help break down the elements in the compost much faster, which accelerates the compost production time. 

Additionally, grubs produce castings, which improve the nutrient content in your compost. Black soldier fly larvae grubs process composting materials that are in various stages of decay, from fresh, right through to almost finished compost. 

Many avid gardeners buy and add compost-grade female black soldier fly larvae (using rubber gloves) to their compost system to produce a rich substance that can be added directly to garden soil. 

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When the grubs mature, they continue to lay more eggs in the compost pile, hence continuing the process indefinitely. 

As the grubs move through the compost, they also aerate the compost via the tunnels they dig as they chew away on the composting banana peels and other organic material, thereby allowing air and moisture to penetrate more deeply.

These tunnels also make room for additional waste materials supplied by grubs through their digestion process. 

Disadvantages of Grubs in Compost Pile 

While grubs are a valuable asset to your compost heap, they can become a nuisance, especially adult grubs present in large quantities. 

If your compost bin is not secured tightly, the grubs can make their way and create havoc in your lawn and garden.

White grubs can cause serious damage to your turfgrass, and their voracious feeding habits can injure your plant roots, causing the grass and plants to wilt and die. 

Adding to this, grubs also attract other pests such as moles, raccoons, skunks, and crows (looking for grubs to eat), and can cause damage to your compost pile or areas of your yard when they dig for them. 

How to Get Rid of Grubs from Compost? 

There are natural as well as chemical methods to get rid of grubs in compost.

Natural Ways of Getting Rid of Grubs 

1. Earth-Friendly Nematodes

Nematodes are beneficial microscopic worms that are a non-chemical solution to getting rid of grubs. These predatory worms work by seeking out grubs in their larvae stages in the compost, and do not pose any threat to pets, people, and plants.

Nema Globe 4003224 Fungus Gnat Nematodes can be used in compost, and all indoor houseplants and tropical plants. They are an ideal preventative measure to kill grubs in their larvae stage, and are easy to use by simply mixing the nematodes in a watering can, and drenching the compost. 

2. Neem Oil 

Neem oil is quite effective against all types of grubs, and also serves as a repellent by inhibiting egg-laying, growth, and feeding. 

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Debug neem oil is a ready-to-use product that kills grubs at all stages. It can also be used for other types of pests including clover mites, flies, and mildew, and is a great dormant spray that works throughout all seasons. 

3. Add Brown Matter to Your Compost Pile

Grubs feast on green material in the compost pile, and adding brown matter like cardboard, dried grass or hay inhibits moisture content. 

You can also alter the chemical composition of the compost by adding lime to the compost pile, which makes it a hostile environment for grubs. 

Chemical Ways of Getting Rid of Grubs 

1.Scotts GrubEx1 Grub Killer

Scotts GrubEx1 is a season long grub killer, and can be added to your compost bin as well as to your turfgrass to keep grubs at bay for up to four months. It kills grubs when they are young, and is easy to apply with a hand spreader. 

2. BioAdvanced 700740M 24-Hour Grub Plus 

BioAdvanced is also another chemical method of killing grubs in the heap, and gets the job done within 24 hours. Apart from grubs, BioAdvanced also kills ants, ticks, bill bugs, and much more. 

How to Prevent Grubs in Compost? 

The best way to prevent grubs in your compost is by adding more brown material and fewer greens, meaning more grass, leaves, and fewer vegetables.

This brown matter distributes the moisture, and makes the compost too dry for the grub’s taste buds. Another good reason to add less green material is that if the grubs get less food, fewer of them will survive after hatching. 

As mentioned earlier, adding brown matter to your compost pile changes its chemical composition by raising the pH levels of the bin and converting ammonium nitrogen into ammonia gas, which is toxic for grubs. 

And lastly, you can buy a compost bin with built-in screens to prevent grubs and other pests from getting into the heap.

Resources;

https://ag.umass.edu/landscape/fact-sheets/black-vine-weevil

https://www.cabi.org/isc/datasheet/5732