Biopesticides: Are They Immune To Resistance?

Western flower thrips  developed to spinosad

Pesticides used in horticultural cropping systems are generally divided into two categories: conventional and selective (alternative). However, it is often difficult to distinguish between the two categories because, depending on your perspective and bias, a selective pesticide may be considered conventional, and vice versa.

Conventional pesticides generally are those that typically belong, although they’re not limited to, the chemical classes organophosphate, carbamate, pyrethroid and neonicotinoid. But what really is a conventional pesticide, and how can it be distinguished or differ from a selective pesticide?

Additionally, what about terms like “biopesticide,” “biorational” and “reduced-risk pesticide.” Sometimes, these, as well as selective pesticides, are also referred to as “soft” pesticides. All of these terms, particularly “biopesticide,” have been used to separate certain insecticides from the more conventional types.

So what are biopesticides? They are pest control materials that are placed into several distinct classes:

The Classes

1. Microbial pesticides (or myco-insecticides). This group consists of a microorganism as the active ingredient. Bacterium, fungus, virus, protozoa or related organisms (e.g., spinosad) all qualify. These are highly selective materials with activity against specific target insect or mite pests.

2. Plant-derived pesticides or plant-derived essential oils (botanicals). These are primarily obtained by steam distillation or by other processes from plant leaves, flowers or seeds. Botanicals may include azadirachtin (derived from the neem tree, Azadirachta indica), pyrethrin (derived from the flower of Tanacetum cinerarifolium) and rotenone (derived from both Derris spp., and Lonchocarpus spp.).

Plant-derived pesticides or plant-derived essential oils act as insect growth regulators, work on the central nervous system or have activity on the mitochondria electron transport system. Many types of plant-derived essential oil pesticides exhibit a broad-spectrum activity against insect and mite pests due to multiple modes of action, such as antifeedant, molting and respiration inhibition, growth and fecundity reduction and cuticle disruption. In addition, these materials have been reported to act on the octopamine pathway within the central nervous system.

3. Biochemical pesticides. These naturally occurring substances are designed to control or regulate insect pest populations by non-toxic mechanisms, such as pheromones (e.g., sex, aggregation and alarm), mating disruption, monitoring and lure-and-kill strategies.

4. Plant-incorporated protectants. These are substances plants produce based on genetic material that is incorporated into plants to render them immune or tolerant of insect and mite pests.

Examples of materials that may be classified as biopesticides include Bacillus thuringiensis, avermectins (abamectin), spinosad, azadirachtin, pelargonic acid, salts of fatty acids and mycoinsecticides (e.g., Beauveria bassiana, Metarhizium anisopliae and Paecilomyces fumosoroseus).

Some of the beneficial characteristics of biopesticides include safety to non-target organisms and mammals; short-residual activity; safety to workers/applicators and less directly toxic to natural enemies (e.g., parasitoids and predators). There are, however, a number of issues associated with biopesticides, including short shelf-life, inconsistent field performance, limited pest spectrum, slower acting (speed of kill) and limited persistence (residual activity).

Dismissing Myths

The fact that some biopesticides are naturally derived doesn’t mean they are safe to humans. Although the short-residual activity is considered a benefit, this means multiple applications are required. This may increase selection pressure on pest populations, possibly leading to resistance.

When resistance is mentioned or stated as a potential reason for failure to control or suppress a given insect or mite pest population, it is generally directed toward conventional pesticides. There are numerous scientific-based publications and trade magazines that refer to insect and mite pests developing resistance to conventional pesticides, and that biopesticides (and even selective pesticides) are immune to insect and mite pest populations developing resistance.

This is absolutely unfounded. First, insect and mite pests are unaware of the differences between conventional and biopesticides. The primary purpose of insects and mites (and other organisms) is to develop whatever means necessary to survive and evolve in order to sustain existing populations. In addition to biopesticides, there are the selective (alternative) pesticides, which may include insect growth regulators, insecticidal soaps (e.g., potassium salts of fatty acids), horticultural oils (e.g., petroleum and neem-based), selective feeding blockers and beneficial bacteria and fungi, as well as other microorganisms. These types of pesticides are presented in the Selective Pesticides sidebar (see above).

The Truth About Biopesticides

Generally, it takes relatively longer (although this depends on the frequency of application) for an insect or mite pest population to develop resistance to a selective pesticide or biopesticide. This is because most selective pesticides and biopesticides have broad or non-specific modes of action, which means these compounds are active on either multiple target sites in or on the insect or mite pest body. Or, the active ingredient attacks a variety of enzymatic or metabolic systems.

As already mentioned, a common claim or misperception published in both trade magazines and scientific-based literature is that biopesticides and selective pesticides are “less susceptible” to resistance. This is not entirely untrue, either. The consistent use of any pesticides or pesticides with similar modes of action will likely lead the development of resistant individuals in pest populations. So, regardless of whether a pesticide is considered a conventional or a biopesticide, insect and mite pest populations may develop resistance due to selection pressure. This is associated with the frequency of applying pesticides and dosage used (rate response).

Why Pests Build Resistance

There are a variety of reasons why insect (and mite) pests may develop resistance to selective (alternative) pesticides or biopesticides. For example, buprofezin (e.g., Talus) has demonstrated to be less effective against the greenhouse whitefly, which may be associated with the “high” volatility of the active ingredient resulting in inadvertent selection pressure. Thus, there is an increased probability of resistance. Furthermore, greenhouses, and even nurseries, tend to retain or restrict insect and mite pest populations with minimal migration of susceptible individuals. This results in the population interbreeding and “passing on” traits to its next generation, which will enrich the gene pool with resistant genes. This increases the proportion of resistant individuals in the population.

Still, it is important to note that this varies depending on the time of year and openness of the greenhouses and nursery. In addition, some insect and mite pests may not disperse very far, which means that concentrated populations of resistance individuals are continually present and may be exposed to pesticide applications. And if pesticides with similar modes of action are used and applications are made on a frequent basis, this will, in all likelihood, allow for more resistant individuals in the population – regardless of whether a conventional or biopesticide is involved. 

Takeaways

It is critical to be aware of misleading information that insect and/or mite pests cannot develop resistance to certain pesticides – in this case, selective pesticides or biopesticides – because it really doesn’t matter what the pesticide is. Insect and mite pests don’t read entomological literature.

Regardless of the pesticide, always exercise proper pesticide stewardship. What is most useful to greenhouse and nursery producers is understanding the biology and lifecycle of insect and mite pests. This will help in the timing of applications and avoid exposing pest populations to pesticides with similar modes of action.

Leave a Reply

More From Insect Control...
Damage to Cannabis Buds from Hemp Russet Mite

October 22, 2017

Take Control of Mites in Cannabis Crops

Mite pests have become a problem for cannabis growers. To reduce crop losses, follow these best practices for better best management.

Read More
Whitefly adult

October 13, 2017

Researchers Continue to Keep Close Tabs on Whitefly

Dr. Lance Osborne of the University of Florida and Dr. Cindy McKenzie of USDA’s Agricultural Research Service are evaluating insecticide efficacy and the impact of product rotations on whitefly biotype populations.

Read More
Biocontrols in a Greenhouse

September 4, 2017

How to Successfully Integrate Biocontrols Into Greenhouse Floriculture Production

The widespread adoption of biocontrol in Canadian floriculture greenhouses grew out of necessity. The lessons they learned can help you incorporate these tools in your production.

Read More
Latest Stories
Damage to Cannabis Buds from Hemp Russet Mite

October 22, 2017

Take Control of Mites in Cannabis Crops

Mite pests have become a problem for cannabis growers. To reduce crop losses, follow these best practices for better best management.

Read More
Whitefly adult

October 13, 2017

Researchers Continue to Keep Close Tabs on Whitefly

Dr. Lance Osborne of the University of Florida and Dr. Cindy McKenzie of USDA’s Agricultural Research Service are evaluating insecticide efficacy and the impact of product rotations on whitefly biotype populations.

Read More
Biocontrols in a Greenhouse

September 4, 2017

How to Successfully Integrate Biocontrols Into Greenhou…

The widespread adoption of biocontrol in Canadian floriculture greenhouses grew out of necessity. The lessons they learned can help you incorporate these tools in your production.

Read More
Aphids On Older Leaves

August 8, 2017

OHP Launches New Insecticidal Soap, Gains New Registrat…

OHP is making two new crop protection tools available to greenhouse growers: Kopa, an insecticidal soap, and California registration for Ancora, a microbial insecticide.

Read More
Cannabis Crop Protection

July 27, 2017

Keep Pests Out of Your Cannabis Facilities

Prevention of pest introduction is the most critical first step in an effective pest management program.

Read More
Aphids

July 7, 2017

New Tools for Your Crop Protection Arsenal in the Green…

Over the past few months, crop protection companies have developed several new products designed to help you manage a wide range of insect and disease pests. Here’s a look at some of them.

Read More
Yellow Stick Card for thrips

July 5, 2017

Tips From a Top 100 Grower for Effective Thrips Control

A combination of conventional materials and biologicals can help provide season-long management of thrips in hanging baskets.

Read More
Scale on leaf nodes

July 2, 2017

Why Biological Control Fails: Encapsulation May be the …

If your biological control isn’t working for you, encapsulation could be to blame. Learn how this defensive response can cripple a biological control program.

Read More
Koppert Ulti-Mite Swirski sachet

June 21, 2017

New Tool from Koppert Provides More Effective Thrips Ma…

A newly patented sachet for the predatory mite Amblyseius swirskii is resistant to both low and high levels of humidity, helping growers combat thrips infestations.

Read More
Cannabis Seedling

May 20, 2017

Biocontrols: A Practical Option for Cannabis

With limited options for chemical pest control, cannabis growers are incorporating biocontrols into their integrated pest management programs. More education will cement this solution as a viable option in this emerging market.

Read More
Four Lined Plant Bug

May 8, 2017

Four-Lined Plant Bug Emerges as Troublesome Pest in Pen…

Four-lined plant bug damage is very characteristic: circular brown to black spots about one-sixteenth of an inch in diameter. The spots are easily mistaken for disease or frost damage.

Read More

May 4, 2017

Bayer Altus Update: Neonic Insect Control Alternative N…

Altus, a butenolide class insecticide with the active ingredient flupyradifurone, will be available beginning May 1, and is labeled for greenhouse and nursery use on ornamental plants, vegetable transplants, and indoor vegetable production.

Read More
Ambrosia Beetle

April 7, 2017

Tips On How to ID Ambrosia Beetle Damage, And How to Co…

Ambrosia beetles are often overlooked as being a primary cause of plant loss, but research and experience are proving otherwise.

Read More

February 28, 2017

OHP Launches New Ovicide/Miticide, Announces Partnershi…

Applause is a new miticide that targets eggs and immature stages of several mite species. Through the Vestaron partnership, OHP will market Spear-O, a toxin-derived bioinsecticide.

Read More
Remote Sensing Feature

February 12, 2017

Using Remote Sensing to Optimize IPM in Greenhouses

Researchers at the University of California Davis are developing advanced remote sensing technologies to automate detection of insect pest infestations in greenhouses, which could revolutionize integrated pest management practices.

Read More
Adult Thrips feature

January 25, 2017

Tips to Stay Ahead of Aphids, Mites, and Thrips

Control these persistent pests with innovative chemistries that will expand your rotation options with new modes of action.

Read More
Effective pest control

January 12, 2017

Prevention and Early Intervention: The Keys to Biocont…

Advance preparation and starting out right helps you implement an effective biocontrol program that reduces pest pressure.

Read More
Two-spotted spider mites, adults and eggs

January 10, 2017

Pest Management Workshop to Take Place in Virginia on J…

Battlefield Farms will host the workshop, which is being coordinated by Virginia Cooperative Extension and will focus on new techniques in disease and insect control.

Read More