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BEACON Senior News

Biological pest solutions for a healthy, diverse garden

May 29, 2024 03:25PM ● By Bryan Reed

Beauveria bassiana is a fungus that that attaches to the surface of insects secreting enzymes that break down the exoskeleton.

A diverse garden is key to growing healthy plants that can effectively resist pests and diseases. By growing a variety of crops, we ensure that plants flower throughout the growing season, attracting beneficial insects. This requires us to nourish the soil, relying on organisms big and small to naturally safeguard the health of the crops.

Biological pest control is a great option. Introducing natural predators to manage pest populations is non-chemical, supports the local ecosystem and can be rewarding as these beneficial species can self-perpetuate.


The most popular form of biological control involves purchasing beneficial insects to eat or eliminate harmful beetles and aphids that cause problems for plants. Sales of beneficial insects have exploded as more gardeners and farmers integrate them into their pest management strategies. 

Ladybugs are perhaps the most well-known beneficial insect. One adult can eat up to 50 aphids per day. 

Parasitic wasps are another popular option. Their stingers can’t penetrate human skin due to their small size, but they have a unique method for dealing with pests: they lay eggs inside problematic insects. As the eggs develop, they feed on the host’s intestines, eventually hatching and emerging from the host, turning it into the wasp’s first meal. The newly hatched wasps then seek out more insects to parasitize, continuing the cycle.

Sound Horticulture is a fantastic U.S.-based source for beneficial insects and has a great website full of useful information.


Beyond buying insects, there are other safe and effective biological controls. 

One of the most widely used is a bacteria called Bacillus thuringiensis (Bt). It can be easily applied using a spray bottle and is highly effective against caterpillars, flying insects and mosquitoes, without harming pollinators. Bt is also the main ingredient in mosquito dunks used in irrigation ponds and livestock water troughs. When pests ingest Bt, it creates crystalized proteins that wreak havoc on the intestines, causing the insects to stop eating and die within days.


A lesser-known but potent control method involves entomopathogenic fungi. The most popular species, Beauveria bassiana, is found in products like BioCeres and Botanigard. It is safe for humans and pollinators but harmful to aphids, whiteflies, thrips, corn borers and beetles. 

While dormant, it forms a thick-walled spore that can be stored refrigerated and shipped. Once mixed with water to activate (using irrigation or distilled water), it can be sprayed onto infested crops. The fungus attaches to the surface of the pest insect and secretes enzymes that break down the exoskeleton. The fungi then infiltrate the intestines, growing mycelial webs that kill the host within days due to nutrient depletion and mycotoxic effects.

In some cases, the fungi target the host’s muscular system, causing paralysis or dysfunction (zombie insects) that lose control of their movements before death. The fungi usually preserve the host’s form after death, then sprout modified mushrooms that release spores to infect new hosts. 

They are most effective in temperatures between 70-90°F and need humidity to hatch. They should be sprayed at dusk when pests are still active but sunlight is fading, as UV rays can damage them. Stressed or densely populated pest populations are especially vulnerable, making this a powerful solution for severely infested areas.


Entomopathogenic nematodes (EPNs) are becoming more popular. Originally soil-dwelling, these worms are effective at managing thrips, leaf miners, whiteflies and fungus gnats in houseplants, as well as grubs, cutworms and webworms. 

EPNs are safe for humans, mammals and other invertebrates. They can be applied using a watering can or hand sprayer, but high-pressure agricultural sprayers can damage them. For best results, apply them quickly so they don’t drown in the water, ideally at sunset. 

Keeping the soil moist for 2-4 weeks after application improves their efficacy. Once they locate a host insect, they release symbiotic bacteria that kill the host within 2-3 days. The nematodes then feed on the host’s remains and reproduce to increase their populations. Research is ongoing to assess their effectiveness against domestic animal fleas, cockroaches, lice, yellow jackets and houseflies. 


For June, optimal planting dates for succession crops fall between the 6th and 19th. Monitor soil temperatures carefully, as levels above 90°F can hinder seed germination. Shading the soil with cardboard a week before planting can help maintain the ideal 60-80°F required for most summer vegetables.

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