Resistance management, Part 1: the differences and similarities between resistance of arthropod pests and plant pathogens.

Pesticides (insecticides, miticides, bactericides and fungicides) are still widely used in greenhouse production systems to alleviate problems with insect and mite pests, and diseases. However, continual reliance on pesticides can promote the development of pesticide resistance. Pesticide resistance is a very important factor that greenhouse producers must take into consideration when dealing with pests (insects, mites and diseases) in greenhouse production systems.

This article is the first in a series of six articles we plan to develop in 2019 and 2020 focusing on pesticide resistance and resistance management for insect and mite pests, and diseases. The first article of the series describes pesticide resistance as it relates to arthropod (insect and mite) pests and plant pathogens, highlighting the differences and similarities.

Resistance is the genetic ability of some individuals in an arthropod (insect or mite) pest population to survive an application or applications of pesticides (insecticides or miticides). In other words, the pesticide(s) no longer effectively kills a “high” number or percent (>90%) of individuals in the insect and/or mite pest population. Resistance develops at the population level and is an inherited trait. Surviving insect or mite pests can pass traits (genetically) to their offspring (young) or next generation, thus enriching the gene pool with resistant genes. In addition, resistance indicates a change in the genetic composition of an insect or mite pest population in response to selection by a pesticide (insecticide or miticide) over time. “Selection pressure” for resistance increases as application frequency increases, especially when insecticides and miticides with the same mode of action are applied in succession. Moreover, the frequency in which resistant genes occur in a pest population determines the rate that resistance can develop.

So, every time a pesticide (insecticide or miticide) is applied, this places “selection pressure” on insect and/or mite pest populations, which consequently alters the frequency of resistant and susceptible individuals in the population. Insect and mite pest populations can develop resistance to pesticides using different resistance mechanisms. The two most common mechanisms are based on metabolic and physiological resistance. Metabolic resistance involves degradation of the active ingredient by an insect or mite pest. For instance, when a pesticide enters the body, specific enzymes detoxify or convert the active ingredient into a non-toxic form. The active ingredient is then excreted out with other waste products. Physiological resistance occurs when an insect or mite pest modifies or alters the target site of the pesticide, which decreases sensitivity to the active ingredient at the physical point of attachment (lock and key scenario). One form of resistance that can occur among resistant insect and mite pest populations is referred to as “cross resistance.” Cross resistance is based on a single resistance mechanism conferring resistance to pesticides in the same chemical class and/or having similar modes of action. Cross resistance is common among aphid and spider mite populations.

The biological factors responsible for promoting resistance in insect and mite pest populations are listed below:

The primary way to alleviate insect and mite pest populations from developing resistance is to rotate pesticides with different modes of action. The mode of action is how a given pesticide (in this case, insecticide or miticide) affects the metabolic and physiological processes of an insect or mite pest. There are two mode of action types affiliated with insecticides and miticides: narrow and broad spectrum. Narrow spectrum or site-specific mode of action pesticides are active on specific target sites in the central nervous system or enzymes associated with metabolism. Broad spectrum mode of action pesticides are active on a variety of target sites or possess multiple modes of action. The modes of action of insecticides and miticides used in greenhouse production systems are available on the Insecticide Resistance Action Committee (IRAC) website (irac-online.org). In addition, the mode of action of a product is listed on the package as a number (e.g., 5, 6 or 28) or combination number and letter designation (e.g., 4A, 7A or 21A).

Dr. Cloyd’s description of why arthropod pests can become resistant to a product are about the same as the reasons for plant pathogens becoming resistant. Bacteria can have a generation time of merely 20 minutes. Fungal generation times range dramatically with some fungi-making spores (reproducing) in a few days to weeks. In addition, some fungi have both asexual and sexual reproduction — like some insects. In this case of sexual reproduction, the genes are essentially recombined, making the possibility of resistance much more likely.

Some plant pathogens also have a very broad host range, which makes it easier for resistance to develop: Botrytis, some bacteria like Erwinia, some powdery mildews and Rhizoctonia and Pythium causing root rot. Others are narrow, like some leaf spots and Fusarium wilt.

The spread of disease is largely passive for plant pathogens, unlike insects, which can move from site to site. Wind (or fans), handling by workers and water are the most common way some plant pathogens get around our growing areas. Examples of plant pathogens moved by water are Pythium and Phytopthora. Those easily moved by wind or fans are Botrytis, downy mildew, rust and powdery mildew. This method of dispersal means that somebody else’s resistance can become yours.

For plant pathogens the keys to resistance management involve a series of issues. First and foremost, the cause of symptoms must be determined. Using the wrong product for a disease results in no control, which can be confused with resistance. Use of the correct product at the correct rate and interval are the best ways to make sure you do not provide pressure on the fungus or bacterium, resulting in the development of resistance. It is well-known that using lower than a lethal dose of a product targets the weakest or most sensitive individuals and builds the proportion of the population with a high level of resistance until it is the only thing present.

Application of a product too often in a program exposes the fungal or bacterial pathogen to a single mode of action, resulting in resistance development the same as insects and mites.

This is especially true if you are using a narrow mode of action product, which does the same thing to plant pathogens as arthropod pests. Tank-mixing or alternating products with the same mode of action does the same thing. It is always necessary to know the FRAC number to avoid this mistake by alternating numbers in successive applications. Using a product with multiple modes of action, which can come from a single active ingredient or a pre-mix of two or more ai’s, is a good way to avoid resistance development.

The next article in the series will address the history of pesticides in regard to the development of resistance to older and newer pesticides.

Raymond is a professor and extension specialist in horticultural entomology/plant protection in the Department of Entomology at Kansas State University. His research and extension program involves plant protection in greenhouses, nurseries, landscapes, conservatories and vegetables and fruits. rcloyd@ksu.edu or 785-532-4750

Dr. A.R. Chase is president of Chase Agricultural Consulting. She has more than 35 years’ experience in research, diagnostics and practical consulting in plant pathology. She has been retired from the University of Florida – Mid Florida Research and Education Center in Apopka since 1994, but remains on staff as a professor emeritus. archase@chaseresearch.net or 928-649-0400

MasterTag understands that it is important to offer flexible options on custom-printed tags. That’s why they offer a program called Group Run. It enables growers to order custom tags in lower, more manageable volume requirements.

Growers often need custom tags with unique or regional content as well as branding. But they also might need more variable data such as bar codes and pricing applied to their tags, says Gerry Giorgio, creative director at MasterTag. That is where Group Run comes in.

“You can order custom tags, taking advantage of many pre-scheduled print runs of our most popular shapes. This allows you to apply unique content or variable information such as bar codes and pricing,” Giorgio says. “And you don’t have to purchase a high volume to get this flexibility.”

Group Run is based on a series of scheduled print runs on some of MasterTag’s most popular shapes. There are many advantages to this program.

With Group Run, MasterTag assumes the responsibility to assemble an efficient print run across a group of growers. This means a lower unit cost, and growers don’t have to purchase tags they don’t need. The program reduces cost and minimizes unneeded tags.

“Everyone can take advantage of the high-volume efficiency, yet get the custom tag suited for your business,” Giorgio says.

Group Runs are frequent throughout the busy production season. Growers can order tags close to the date they need them and better manage their production inputs.

Group Run offers flexibility. Growers can take as many or as few positions as they need on a given Group Run. It’s even possible to combine different varieties and designs on a single Group Run for maximum options in ordering custom tags.

Here is how Group Run works:

Unfortunately, even the best growers can accidentally over-apply their PGRs. Maybe it’s a miscommunication among the production team; perhaps it’s a miscalculation by an inexperienced applicator. Too much of a growth regulator like uniconazole or paclobutrazol stalls out plants, resulting in missed sales windows or in the worst case, discarding an entire crop. But now, growers have a tool to help address the issue.

Fine Americas has revealed that in addition to functioning as a plant growth regulator, its Fresco product also works great in crop rescue situations. For example, if a grower overapplies paclobutrazol, uniconazole or other PGRs, a Fresco drench can help snap plants out of the delayed flowering and growth that follows.

As little as a single drench can save a crop. If you don’t see expanding leaves and stem elongation after five days, consider a second application.

The bottom line: Fresco, a combination PGR — with both the active ingredients BA (benzyladenine) and GA (gibberellic acid) — can kickstart stalled young plants, along with its known ability to encourage plants to grow and form structure.

That means that rather than sacrificing a whole production cycle, growers could be able to save their crops.

Fresco is registered for most ornamentals, such as chrysanthemums, gardenias, azaleas, hydrangeas, poinsettias, petunias, marigolds and others.

For 90 years, Lambert Peat Moss Inc. as been offering a wide range of peat-based products from various grades of Canadian Sphagnum Peat moss to one of our assorted ready to use professional mixes. The company has been dedicated to meeting the special needs of professional horticulturists, greenhouse growers, vegetable producers and amateurs.

Because we want to meet and exceed the expectations of our customers, we make sure we choose only high-quality ingredients after a rigorous selection on the bench test by our quality control department. By selecting the best available components, it’s a good start to produce “no worries” products for our customers!

With our special way of screening and then blending our professional peat grade with those selected components, we can achieve a unique consistency for the professional growers. Lambert wants to make sure that your mix is exactly the same, batch after batch, year after year. That way to proceed allows you to keep the same formula on site so you can produce a successful crop. The best way to solve a problem is to make sure it will not appear!

That’s why quality is our top priority. Our quality control department performs continuous sampling and analysis during the production of your mix. Each sample is analyzed for pH at three different incubation stages, and the same goes for the electrical conductivity. Particle size distribution, moisture content and yield complete the criteria we constantly evaluate. We make sure that each cubic foot of your mix is in total conformity with all our specifications. If one of these points is not completely encountered, it will not be released for delivery by the laboratory staff. Only top-quality product will leave our yard!

However, as each greenhouse experiences a different environment, some “problem” or specific conditions can occur. Again, you can rely on Lambert’s team to help you resolve your issues. By customizing your mix for a specific rate of nutrients or components, incorporating a biofungicide or producing a specific pH order, to name a few, it makes your production easier. We own a complete on-site lab so we can perform soil analysis for you at different stages of your crop to see the evolution of the situation and target what’s going on.

Wherever you are located, one of our sales representative team isn’t far away. With most of them experienced previous growers or greenhouses owners themselves, they will be able to listen about what you’ve been experiencing and help you gather information to find the perfect solution and resolve any issue.

Moreover, Lambert Peat Moss Inc. has developed a large efficient and versatile distribution network ready to make the impossible to deliver the product at your door in an incomparable timeframe. The constant commitment to improve and optimize its customer service allows Lambert Peat Moss Inc. to adapt quickly to the requirements of its customers. The skill and dedication of its staff ensure that it remains competitive, at the cutting edge of the technology and at the forefront of markets by offering incomparable quality products.

The Haifa Group, a leading supplier of specialized fertilizers, makes products that simplify growers’ lives. 

“When growers come to us, if there’s a product that matches up with the problem we are dealing with, we’ll point them in that direction,” says Haifa grower specialist Scott Todd. “We’ll help them figure out what rates to apply it at and give them a good general rate to start out with.” 

One such product is the Multicote controlled release fertilizers (CRFs). According to Todd, Multicote products offer the following benefits for greenhouse growers: 

As for the CRFs, Todd says that they can include one single nutrient source, such as potassium nitrate, or a combination of nutrients. He adds that they also reduce labor needs because they require a single application. Growers can also purchase custom blends to fit their specific needs. Additionally, information about CRFs, including video demonstrating how they work, can be found at haifa-group.com/controlled-release-fertilizers-crf

Other Haifa products that help growers succeed are its water-soluble fertilizers, which Todd says have the ability to correct nutritional deficiencies in plants. All of Haifa’s water-soluble fertilizers are: 

“Our water-soluble fertilizers are highly versatile,” Todd says. “They allow you to pick and choose based on the issues you have with your crops. Let’s say you need to raise your levels of phosphorus and potassium, or correct a deficiency of these elements. You can achieve this with our MKP product which allows you to apply just the P and K by themselves to help fix the problem.”