Compost Bin Pest Troubleshooting
Pest troubleshooting in your compost bin
Sometimes, a compost bin can become an unwelcome habitat for other natural creatures in your yard. Read on for advice on troubleshooting the most common pest occurrences.
Easy Ways to Rat and Critter-Proof Your Compost Bin
A common misconception and one we are often asked about is whether composting will attract rats. Rats are quite prevalent in San Diego, particularly roof (or tree) rats. Palm tree and other dense vegetation (bougainvillea, honeysuckle) provide ideal habitats. Food is often supplied from fruit trees, vegetable gardens, and bird feeders.
It is important to note that composting will not encourage pest populations to move into your area, though a neglected pile may attract local populations and make them more visible to you. Studies have shown that pests, including rats, were the third most common composting obstacle—following lack of space and lack of knowledge. Pest problems should not be underestimated, but there are a few simple measures that can help to keep pests from getting in or being interested in your compost pile. The best solution is prevention! Pest-proofing your bin can prevent animals from tunneling up through the bottom, climbing into the bin from the sides or top, or chewing holes in the bin. Below are some tips:
Use hardware cloth to line the bottom and outside walls of your bin. For mice, 0.5 cm (1/4 in), 16 gauge should be used; 1 cm (1/2 in), 20 gauge for keeping out larger pests. (Hardware cloth is galvanized wire mesh, available at most home improvement/hardware stores. Chicken wire is not a good protection against unwanted visitors).
Get a tight-fitting lid or modify your existing lid by adding hinges and a latch. Or stretch a bungee cord or chain across the lid and fasten it to the sides of the bin. A heavy brick or rock will also keep the lid secure.
Pile rocks or bricks around the outside bottom edge of your bin as a good measure against burrowing animals.
Alternatively, you could consider purchasing a rodent-proof bin that is already fitted with such deterrents.
Covering all food scraps is your best defense! When adding food scraps, dig a hole in the center of the pile. Then, add alternating layers of nitrogen and carbon (aka Lasagna Composting), always ending with a carbon layer, which serves as a blanket and keeps flies from laying eggs on the exposed nitrogen material, and masks the odor of food waste from other animals. Placing materials that are high in carbon (i.e., dried leaves) at the bottom of the pile and along the inside walls of your compost bin will provide good airflow, drainage and odor control. It is also important to harvest finished compost at the bottom of the bin every three to six months. This will discourage pests from nesting in the warm finished compost.
It is also recommended to not add meat, cheese, or leftovers containing excessive oil or seasoning. These creatures are attracted to meats, fatty foods, and cooked foods, so it is best to exclude these from your bin or pile. These animals are also looking for other food sources (i.e., bird feeders, outdoor pet food bowls, garbage cans, and fruit trees). It is a good idea to position your compost bin away from these other food sources and nesting locations! Good compost management can deter pests while also accelerating the composting process. By being mindful of what you put in your compost bin and how you manage it, you may prevent these unwanted visitors. Every time you aerate or turn your compost pile the temperature increases, which will both speed up decomposition but also deter these animals that are looking for a dry, cool, undisturbed home and food source.
For composting projects in areas where rodent activity is high—the use of fully enclosed bin systems may be your best option. If using an open pile, it is especially important to fully cover, or cap, any active compost piles with a biolayer: at least 2 inches of finished compost, at least 6 inches of unscreened compost, or 12 inches of wood chips, to avoid attracting rodents.
Deny Habitat
Enclosure – fully enclosed bins, particularly tumblers.
Raise bin off ground (for burrowers).
Place bin on a concrete or sand base.
Hardware cloth – use to place under bin and/or line bin.
Reduce clutter.
Properly store feedstock and/or garbage.
Rats are attracted to prior rodent infestation, using urine as an attractant. You may need to power wash hard surfaces to remove signs of rat activity.
Deny Security
Rats don’t like open spaces. Keep compost bins away from a fixed wall or fence.
Don’t create harborage (safe shelter). Dense vegetation often provides rat habitat.
Rats only need a space the size of a quarter to gain access. Find and seal all external holes in garages and sheds to keep rodents from getting in. Use rodent-proof materials: ¼ inch 18-22 gauge wire hardware cloth.
Deny Food
Avoid composting meats and oils.
Bury fresh food waste 6 inches deep (open pile system).
Cover with finished compost (open pile system).
Properly store feedstock and/or garbage. Don’t leave birdseed and pet food out at night.
If your yard has fruit trees, nuts or vegetable gardens, make sure you pick food as it ripens. Don’t leave fallen fruit or vegetables lying on the ground.
Encourage predators (owls, hawks).
The use of poisonous bait is never recommended because it can endanger the lives of pets and other wildlife. The use of glue traps is just plain cruel.
For more info or questions specific to your property, call our rotline at (760) 436-7986 ex. 700.
How to Save Your Worm Bins From Aggressive Ants
How do you save your worm bins from aggressive ants? To find the answer, we asked our summer college interns, Maddie and Kelly, to investigate. The worm bins at Solana Center recently experienced an increase in ant populations, possibly due to the decomposing food source and the moisture the bins provided. Although most species of ants will not harm the worms (other than depleting the worms’ food source), the ants in our worm bins were aggressive and ended up killing some of our worms. We researched a few options for discouraging the ants from getting into our bins and decided to test the different methods. The various methods primarily revolved around reducing access, using either vaseline, diatomaceous earth, or a bait trap that was safe for humans.
One way to protect the worms is to create a barrier that the ants won’t cross. Diatomaceous earth is a repellent capable of killing ants which can be easily spread around your bins. The white chalk-like powder is derived from fossilized shells of diatom, an ancient marine algae. The diatom’s exoskeleton is made from silica which, as a powder, is a useful insecticide. When in contact with an insect, the diatomaceous earth will stick to their exoskeletons, leaching out and absorbing any moisture which will dehydrate and eventually kill the ants. Although chemical-free, this substance serves as an effective treatment for insect infestations. Due to our aggressive ant problem, our bins were overrun and the worms were under attack. By outlining the perimeter of the bin area with the diatomaceous earth, the ants were unable to enter the bins.
You can also apply a sticky coating, like petroleum jelly or Tanglefoot, to the base sides of the worm bins to keep ants out. The layer of petroleum jelly will prevent the ants from traveling up and into the bins. The petroleum jelly protection will wear off, so periodic applications are necessary.
Like many pests, ants are attracted to sugary substances. Ants are specifically known to swarm sugary foods because sugar is extremely lightweight and high in calories. We decided to devise an ant extermination trap using the attraction of peanut butter and jelly-filled bottles. We filled plastic recycled water bottles ¼ full with a mix of peanut butter, jelly, and water, and drilled small holes halfway up so the ants could access the mixture. We placed these bottles a few feet away from the worm bins. The concoction is designed to distract the ants away from the worm bins by offering the ant colony a new food source. When the ants increase in numbers after a couple of days, we added boric acid into the water bottles to kill the ants. Boric acid is a natural mineral, also known as sodium borate, sodium tetraborate, or disodium tetraborate. The mineral is found in sediment known as evaporite deposits, concentrated after lakes undergo repeated evaporation. Boric acid is safe for humans and animals in small doses, however, the mineral fatally interferes with an ant’s digestive system.
If ants are attacking your bins, hopefully, some of these convenient, safe, and affordable methods.
How to Manage Bee Swarms in Your Compost Bin
What Should You Do First?
Many of us know that bees serve a vital role in the environment as pollinators, and that their populations have seen a concerning decline in recent years. However, it can still be alarming when a swarm of honeybees chooses to land around our home– including the inside of a compost bin! This happened recently in one of our backyard bins here at Solana Center, so we’d like to help you understand why swarming occurs, and what how to humanely deal with a swarm.
Why do bees swarm in the first place?
Honeybees are social insects that live in colonies of up to 60,000 individuals. However, each hive can only house so many bees, so when space gets tight enough the colony decides to split. Swarming is therefore a good thing: it means that the population is growing! The queen, who is the only egg-laying member of the colony, lays an egg for another queen. Once the new queen is ready to lay eggs herself, one of the queens heads off with about half of the colony to start up a new hive. This is what is referred to as “swarming”: a large group of bees with a queen, searching for a new home.
Are swarming bees aggressive?
As intimidating as a large cloud of energetic bees can be, please note that swarming bees are not aggressive. Bees’ instinct to sting comes from a desire to protect the hive from danger. However, when swarming, the bees have no hive to defend and will not sting.
What can I do about bee swarms in my compost pile or around my home?
Call a beekeeper or bee removal company, NOT an exterminator! Since bees are both vital and threatened, please do not call an exterminator, which will kill the bees. Choose a resource that offers humane relocation of bees so that the colony can find a safe new home. One option serving San Diego County is AA Beekeeper.
If you’re feeling brave, remove the lid of the compost bin at night. Especially if the colony has just moved into a bin and hasn’t settled in yet, exposing the colony may encourage them to seek out a safer home. You can do this at night when the bees are less active, then you can head inside to leave them to sort it out. However, note this may only be a temporary solution, as they could seek out an equally-incompatible location around your home.
Prevent bees from entering the bin. You can bee-proof your compost bin by covering any bee-sized or larger openings with mesh; just make sure you aren’t limiting airflow to the pile. Or, consider leaving the lid off the compost bin during spring and summer when swarming is most common. If you choose to do this, ensure you have a thick, moist topper covering the compost so it won’t dry out.
Too many slugs in my compost bin!
Do you have too many slugs in your compost bin? In a spray bottle, mix in 1 cup ammonia to one quart water. Go out at night and spray slugs wherever you find them. Ammonia will have no affect whatsoever on your compost. It will only kill slugs and snails. If you go slug hunting in daylight, check under rocks, pots and lids, any dark moist hiding place. You can somewhat trap them by placing said hiding places in proximity to the bin.
Even though slugs contribute to decomposition, they tend to stray from the bin into the garden. Many people find this unsavory, so if you have too many slugs, fill up your ammonia sprayer and take it to ’em.
What are all those different grubs in my compost heap and should I be worried?
Many people are alarmed to find grubs taking up residence in their compost heaps, and the large population can worry some. Don’t worry, these guys are probably nothing to fret about. Most likely, they’re doing exactly what you want them do, which is EAT! They consume your organic matter and in turn leave you an abundance of nutrients. The grubs are beetle larvae and there are several types that can inhabit your compost heap.
Large grubs like you describe are most likely the larvae of the big iridescent green Figeater beetle, Cotinis mutabilis, a noisy, bumbling aviator. The larvae feed on decaying matter so there is no worry that they will eat your plants. The mature beetle feeds on sweets such as sap, flowers and over-ripe fruit. The larvae can be up to two inches long with rows of bristles on their back. They use the bristles for walking on their backs and are sometimes referred to as ‘Crawly backs’. They are harmless to the garden with the adult green fruit beetle eating only rotting fruit, so you don’t usually have to worry about them being pests in your garden. More information about Figeaters can be found on the UC Pest Management website.
The Figeater beetle is frequently confused with the Green June Beetle as well as the Japanese Beetle. The Green June Beetle, Cotinas nitida, is the Figeater’s East Coast Cousin and looks very similar as both an adult and larvae, but can damage the garden. Fortunately, this guy only lives in the Eastern half of the USA. The Japanese beetle, Popillia japonica, is an exotic pest that has caused a lot of damage on the east coast. The San Diego County Pest Detection Program places traps for them around the county in the fall as a part of a nationwide monitoring program.
Fortunately, these nasty hitchhikers haven’t largely established themselves in San Diego County. The larvae of The Japanese Beetle can be distinguished from the aforementioned beetles because it possesses a set of legs near the front of the grub. If you do come across them you should be careful to screen them from your compost. You can also pick them out and feed to the birds (chickens love them!). The larvae of the green fruit beetle (aka the figeater) are large C-shaped white larvae about 2 inches long with gray rear ends. The larvae are nicknamed “crawly backs” because they wiggle on their backs with their legs in the air.
If you still prefer to limit the larvae population in your compost, try burying your “Nitrogens” under a few inches of “Carbons” so the adult beetles and flies won’t be attracted to your heap. This will also help manage house flies and fruit flies.
Another common grub in a compost heap is the larvae of the black soldier fly, and it is also beneficial in consuming nitrogen-rich organic material such as your food scraps. You will find the larvae inhabiting the top couple inches in your compost. Young soldier fly larvae are a gray-white color, segmented, about an inch in length and very active. As they mature they turn a dark brown color. They are torpedo-shaped and flattened, with tough-looking skin covered in hairs and spines. The larval body bears no legs. The adults are also harmless. They live only a couple days, feed on your food scraps and lay their eggs in the compost.
