A Generalized Integrated Pest Management Program for Aphids in Public Rose Gardens.
By William Olkowski Phd.
Outline:
INTRODUCTION
Some Biological Facts to Start With
Figure A. The Rose Aphid Life Cycle (make one up with the wingless females indicated from the overwintering egg).
What No Mating? So Sad.
Asexual Reproduction Speeds Up Reproduction
A Secret Entomological World
Natural Controls on Rose Aphids
Designing Your Own IPM Program
Rose Aphids are Not that Important for Plant Health
The IPM Algorithm
Honeydew, the Manna from Heaven
Insects Present
Plant Damage Present
Monitoring, the Most Important IPM Component
Figure x: the Natural Enemy Lag Problem
My First Rose Garden IPM Experience
Ants Can Interfere with Natural Controls
Carnivores Effective?
Pictures of Orius, larvae or life cycle of lacewings and ladybeetles see CSPC
The Most Important Organism on the Earth are Not Humans
Figure Z. Pic of mummy
Control Feasible?
The Treatment Sieve
Table 1. Strategies and Tactics Useful inPestControl. See CSPC.
Biological Control (BC) Feasible?
Classical BC
Plant Replacement
Tell Conclusions to the Manager and Clientele
end
A Generalized Integrated Pest Management Program (IPM) for the Rose Aphid
in Public Rose Gardens
By William Olkowski, PhD.
INTRODUCTION
IPM can stand for Intelligent Pest Management or as it is more commonly known, Integrated Pest Management. It takes little brain power to buy a powerful insecticide and kill animals. Plus, insecticide use is fast and convenient if one disregards the need for spray-safety equipment, and the contamination of the environment. Intelligence is required if one wants to avoid the toxic products which have now contaminated the soils, air, water and food chains of the planet, as well as most human bodies. But insecticides can be useful if placed properly within a least toxic program. This article describes how to design a least toxic IPM program for the rose aphid in public rose gardens. As such it can be taken as an example for the development of similar programs for other pests of roses and for other pests in urban settings.
IPM is an Intelligent Approach to Pest Control
Intelligence is not a product but a sign of a good thinking process at work. With thought, experimentation and work, a least toxic pest management program can be developed for all pests. An attitude and knowledge is required, however. The attitude part of the process is based on the desire to learn and be gentle with the natural world that this aphid species represents. Knowledge of life cycles, natural controls and the proper interpretation of observations make the job a bit more complicated than reaching for the poison, but much more satisfying. Living with the natural world is the idea, not domination of it. We are part of the natural world and it was not created for us alone. That goes against a whole body of history, but it is rational. Maybe IPM could be called RPM, Rational Pest Management.
Some Biological Facts with Which to Start
In different parts of the country the near universally distributed rose aphid, Macrosiphum rosae, lays eggs on the overwintering canes which give rise to wingless young in the spring, and after a short time these grow into wingless or still later in the fall, winged adults. Before the so called modern era which brought us the DDT’s of the world, this fact was used by intelligent managers to cut the canes down just before the winter. This reduced the spring aphid populations. The practice, however, is only temporary, of course, as aphids are evolutionary smart little critters with some critical tricks for survival. See Figure A for a complete generational life cycle for this particular aphid.
Figure A. The Rose Aphid Life Cycle (make one up with the wingless females indicated from the overwintering egg).
Rose aphid adults then continue laying wingless young without the need to mate. In characteristic fashion entomologists have special terms for these life stages. Young are called nymphs, which has always engendered in me a vision very different from these wingless sap suckers. Adults and eggs have no special terms, yet. But winged aphids have the adjective alate attached to designate wing forms. So with most aphids we have alternating morphologies, winged and wingless. Things in the natural world are not simple.
What No Mating?
These first generation animals have an unusual life cycle even for most insects. The wingless young develop into wingless adults during the hot summer months. These give birth to more living aphids without the need to mate. Then winged male and female adults appear in the fall, but these mate and the females lay an overwintering egg. So most of their life they reproduce asexually which means they are genetically identical to their mothers. Thus all populations are made up of mixes of clones. This feature occurs here and there in the animal kingdom, some lizards do not mate, for example. And some critters are hermaphrodites, a characteristic claimed for mythical beings in some belief systems.
Nature experimented with different types of reproduction a long time before we humans arrived. I wish we humans knew what these dumb little animals learned during their evolution. Hopes could drive knowledge acquisition, maybe.
Asexual Reproduction Speeds Up Reproduction
In cases where no eggs are laid, adults fly into the rose garden from other areas and start to lay living young. The ability to reproduce without the need to mate speeds up population growth and accounts for very high numbers early in the season. Then the cloning process continues through the summer months until the fall. When you see a single winged adult you are really looking at 3 generations. These winged “alate” adults have babies inside which also have babies inside them, all ready to go out the door, so to speak. This characteristic is called telescoping generations.
The newly born young can develop rather quickly into fully mature adults at optimum temperatures. Aphids in general can reproduce at lower temperatures than many other insects and consequently get a head start in the cool early spring mornings.
Thus, most of the year the aphids are reproducing asexually and can do so rapidly that one can be surprised by excessively high early populations. In places where eggs occur they are the result of mated females who lay eggs in the fall. At these times, in response to changes in sunlight, sexually mature wingled females and males develop, mate and the females deposit overwintering eggs. Such eggs are thought to be the reason why so many exotic aphids have invaded from foreign lands as they can sneak in with plant materials when the plants are imported, for example.
We are the main invaders toNorth Americaas any living American Indians must know. And we brought our plants with us. But back then, nobody was looking for these tough little overwintering eggs. Even today new aphids invade. The rose aphid may have arisen inEurasiaas that is where roses are thought to have been domesticated. (Need refs, see wiki first).
This egg fact has two consequences for the pest manager: 1) overwintering eggs can be a target for control efforts with cane removal and oil applications in the fall; 2) as most overpopulated pest species are exotic, they can be controlled by reintroducing the biological controls present in their native areas.
A Secret Entomological World
The process of importing the original natural enemies from the native area of the pest is called classical biological control (BC). It is probably the most hidden secret in pest control. Many entomologists are only now discovering this secret and most entomologist can’t yet use this process, particularly the classical tactic. This is understandable as to participate in such biological control projects requires special quarantine laboratories and accurate identification. Other BC tactics, however are generally useful (see further below) and are sold through commercial companies.
Unfortunately, few scientists work on such natural enemies. In a curious twist of fate, most of the natural enemies, particularly of aphids, are among the most common creatures on earth. They remain unexplored mostly, while we continue using vast sums of money and resources looking for life on other planets, and how to kill things. Most of the life on this planet is still unlisted and if listed the list is too short and most of the species are biologically unknown. But this listing process is now being explored with NSF funds and is part of a process called Encyclopedia of Life (eol.org) stimulated by the great E.O. Wilson, so well known for his work with ants and the field of sociobiology (See Ants, Sociobiology, and Superorganism). His latest book explores the development and evolution of social species by comparison between social insects and primates, particularly humans (The Social Conquest of Earth).
Natural Controls on Rose Aphids
Natural controls regulate population sizes. Natural controls on rose aphids arise from the environment, the plants themselves and from natural enemies. These controls can be used by the intelligent garden manager. Plant resistance is evident from an examination of population sizes on different plant varieties. Old rose varieties (frequently those with open yellow flowers) are less susceptible to aphids and plant pathogens. But rose garden managers need to do their own observations on the varieties under their care to select those for emphasis in their displays. The more susceptible varieties need to be discouraged where possible, but for those special varieties you can’t cull, they can be placed in less conspicuous places where their pest problems are not so visible.
Seeing large numbers of aphids on stems, rose buds and leaves so soon after your first look in the spring can lead to an immediate concern for the rose bush and pesticides are rushed into the battle. In most cases, this is not the least toxic way to manage the problem. There are better ways but within a more inclusive IPM mental framework as termed above.
Keep commercial pesticides to a minimum if they are needed at all. That’s the least toxic way. Too many pest control people think IPM means mixing pesticides, in the same tank, in combinations or sequentially on the plant. That’s not the right stuff. Insecticide resistance is widespread and leads to the pesticide treadmill my old teacher, Robert van den Bosch, describes so aptly in “The Pesticide Conspiracy”.
Designing Your Own IPM Program
Every rose garden is different and every situation is different so I think it is better to teach people to design their own IPM programs. My logic is based on the Fishing Paradigm. I call it this because the idea is held in the commonly repeated reframe about teaching how to fish is better than giving someone a fish. So, with the right stuff, each manager can design a program for their own ecosystems because a process for designing such programs is more generalizable to more situations since every place, every ecosystem, certainly every garden, is different. Learning how to fish can feed a person for a lifetime, but a gift fish is only good for one or two meals at best.
A recipe based approach fails in the long term and leads to pesticide resistance, but an IPM approach can be redesigned at every turn with learning from previous experiences. The IPM learning process is not complicated but requires a reorientation from the simple see-bug –kill-bug idea which the commercially purchased insecticide sellers teach.
More money can be made by servicing the problem than solving it. One of the worst practices taught by these sellers is the use of combination products like fertilizers and various “cides”, be they herbicides, insecticides, or fungicides. Combination products lead to waste and resistance as they are commonly used when one of the combination is not needed. Such mixed products are common, unfortunately.
Rose Aphids are Not that Important for Plant Health
Aphids on roses are not big killers, they are nuisances. The IPM garden manager is not greatly disturbed by aphids on roses because simple non toxic and least toxic solutions are available. Water washes can be used right away and this can buy time for further analysis and observation. One must learn how much water pressure to use however and must chose the right nozzle and its adjustment to wash off the aphids but not damage the plants.
With water washes there is time to learn how best to manage the problem if it persist as intolerable. The rose aphid is more an aesthetic consideration than a plant health issue. Public rose gardens are usually considered as exemplars where no bugs are tolerated as they reflect on the manager. Changing this sort of thinking is not easy and is a major barrier to a more ecologically sane approach. But frequently the job description and performance expectations need adjustment. These are a human construct, and when changed, can provide new incentives for capable managers to make the necessary changes in the pest program management. If the boss wants immaculate roses there is no room to use IPM. When we were implementing pilot IPM programs we went around this problem by going to the top of the bureaucracy in question and instituted an IPM policy. Usually there was no previous policy and decision-making was left to field personnel.
This can be a disaster or even a benefit depending upon the bureaucracy. Public pressure can influence these upper levels, while field personnel are insulated from such pressures, for the most part. But field personnel do think about their health and exposure to toxic materials which require safety equipment and procedures can be disincentives and, as such, make their jobs vastly more complicated.
The IPM Algorithm
The algorithm in Figure x (from Shade Tree chapter in CSPC) encapsulates a whole systems view of what IPM can be. I and my associates tested this system for over 30 years in a wide variety of ecosystems, including at first in the City of Berkeley California, on Shade Trees, Parks and the City Rose Garden. There are a series of features for this algorithm which make it particularly fitting for urban pest systems. These features are 1) the type of triggers for monitoring, 2) the involvement of ants and 3) the idea of plant replacement. These features differ considerably from those advocated for agricultural IPM, the main research focus for most economic entomologists. I suspect, however, that aesthetic considerations also operate in agricultural settings.
The monitoring component for this algorithm is triggered by three questions which are all aesthetic concerns: honeydew present, insects, and plant damage visible.
Honeydew, the Manna from Heaven
Honey dew is an essential feature of aphid colonies and this sweet pertinacious excretory product is food for beneficial insects including many aphid natural enemies. By watching for this shiny sticky substance on leaves one can detect early small aphid colonies. Without honeydew falling on leaves in the forest biological controls cannot function properly. Lacewings, ladybeetles, and many parasitoids need protein to lay eggs, for example. Honeydew supplies protein for building tissues and sugars for supplying fuel for metabolism. Now this fact creates a quandary.
Aphid presence means honeydew and honeydew brings natural enemies. Having both is the ideal, but not too much of either honeydew nor aphids. Tolerance of some bugs is vital, however. Just when does tolerance meet intolerance is a management decision. That’s the key question, dear Hamlet.
Insects Present
Insect presence alone cannot be harmful. Seeing an insect or even a colony of bugs anywhere is not necessarily a bad thing. It’s us who make this judgment. What comes first to my mind in making such a judgment is a Chinese classical painting of a grasshopper sitting on a leaf with a few holes in the leaf and a bamboo stalk. It’s a beautiful vision. Grasshoppers are part of the natural world. One grasshopper is not a calamity. Vast numbers of them could be, however. The pestiferous nature is decided by whether we have so many that life becomes impossible. Even loss of an entire rose bush does not challenge the free world, however. Like Woody Allen’s heroine says in Whatever Works: “Relax, there’s nothing faster than the speed of light.”
Plant Damage Present
Plant damage alone is only a possible indicator of a pest problem. Alone, at a low level plant damage is not a threat, particularly if natural enemies are already eating on the colony. A little plant damage is actually stimulatory to the plant.
Insect presence, like honeydew and plant damage are only triggers for more attention, so once detected further monitoring is needed.
Monitoring, the Most Important IPM Component
Monitoring and the answers derived determine whether the particular pest is or will become intolerable. This is the key to most pest control situations. I am at a party and someone comes up knowing I am a pest control specialist, asks: “What can I do about my African violets?” I ask “What appears to be the problem?” She/he says there are these white specs on the leaves. Maybe I probe a little further but finally get to the key question: “How bad is it?”
In many cases they say: “It’s not so bad but I am worried”. So my answer in many more words is: “Call me when you can’t take it any longer”.
So by peeling away a great many minor problems, much less pesticide can be used, sometimes 100% less. It’s amazing to think that many, many people are spraying unnecessarily. Fear of insects maybe in part the blame, and this is engendered by unscrupulous business people but also by knowledgeable people who go for the quick fix. This 100% reduction can be achieved is given the knowledge that natural enemies always lag behind the pest population. With a little more tolerance they will do all the work necessary to control the problem, but one must be able to recognize these species and judge how much impact can be expected from their feeding.
When some aphids survive a water washing, for example, many predators will eat the remaining aphid colony and move over to other pest problems and prevent outbreaks there. Many pesticide applications can be prevented with a little insect tolerance and careful monitoring. Plus, this is a window into the natural world, something we all need in our education, maybe in our lives, judging by how common pets are for living the good life. Insects as pets are part of many cultures, crickets, for example are pets inChina(see Box Q).
Box Q. Crickets as pets
From Wikipedia, the free encyclopedia
A pet cricket and his container made of agourd. Watercolor by Qi Baishi (1864–1957).
Keeping crickets as pets emerged in China in early antiquity. Initially, crickets were kept for their “songs” (stridulation). In the early 12th century the Chinese people began holdingcricket fights.[note 1] Throughout the Imperial era the Chinese also kept pet cicadas andgrasshoppers, but crickets were the favorites in the Forbidden City and with the commoners alike. The art of selecting and breeding the finest fighting crickets was perfected during the Qing dynasty and remained a monopoly of the imperial court until the beginning of the 19th century.
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Figure x: the Natural Enemy Lag Problem.
The natural enemy lag problem is a most important aspect of garden pest control, but it is frequently never considered. If one only treats the most severe pest problems, already showing or those anticipated to will show intolerable plant damage the percentage reduction in unnecessary pesticide use can go up to over 90%, and even higher. That is why spot treatment, even with conventional pest control tools, can be a major way to reduce pesticide use.
My First Rose Garden IPM Experience
On my first visit to the Berkeley Rose garden many years ago the smell from the routine insecticide and fungicide applications over the whole collection of plants was overwhelming and most disturbing. I don’t make a habit of smelling pesticides as that means I am getting a lung dose of some unknown poison. Roses were considered in that particular garden as sort of sacred beings, untouchable, static, virtually icons, that is, even before icons became internet features.
This icon idea about horticultural creations is a bad idea. Nature is not static and to make a collection of plants like a fixed photograph is unnatural, most ignorant of how natural things work, stupid even. This attitude arises from the idea of dominating nature, our task as humans, much like the White Mans Burden of 18th centuryEngland. The upper class gardens, particularly public display gardens, for example, say in Versailles in France are not the best we can do. To mimic this ideal is foolish for it leads to having to support the unsupportable with the pesticide crutch.
I did not tell the rose garden manager all this at first but it was rattling around my mind. I needed this guy as an ally so I suggested some useful practical things, first spot treatment with water, second pulling some highly susceptible plants out, moving some others to poorly visible places where they could sustain more damage without hampering the visibility of the rose blossoms. And I said to him: “those pesticides can damage one’s health, some people can tolerate exposures better than others but we don’t know why”. I am sure he heard that part. Older people worry more about health than youngsters. The manager was not a youngster, so I tried this gambit.
Ants Can Interfere with Natural Controls
The ant association with honeydew producers can be a most difficult complication which is overlooked by many garden managers. That’s because ants can be sneaky. Here inCaliforniathe Argentine ant (AA) has spread north along the coast and riparian corridors into theCentral Valley. It likes living under warm and protected side walks from where they forage into the nearby shade trees so conveniently planted by city forestry departments. In my early surveys inBerkeleyevery tree species inBerkeleyhad trails of this ant going up the trunks, and that’s over 100 species.
This ant species is an invader to North America, having spread from its initial port of entry, New Orleansin 1871, arriving from South Americain coffee shipments. It’s present in most Southern states from the West coast to the eastern Atlantic states. I first viewed this ant as a pest and made a pilgrimage to visit and present my thesis work at the Tall Timbers Research Station in Floridaback in 1970s. The pilgrimage was to simultaneously meet the great entomologist, “Willy” Whitcomb, then an entomological rebel. Anybody who can remain a rebel in Academia is worth respect. My old teacher, Robert van den Bosch called him Willy and I am continuing the tradition out of respect. Willy’s specialty was spiders and ants, particularly fire ants (see http://gap.entclub.org/taxonomists/Whitcomb/ index.html).
My first conference lecture was about the algorithm described herein and it was received without criticism, and a polite applause as is customary. I got some comments and questions privately, always a good indicator. Later, Willy assured me that there was a natural enemy for the Argentine ant: “Ants are ant’s worst enemies.” This was his cryptic remark to my quiz. With some further discussions I learned about an army ant that he saw tunneling under the soil surface to native Argentine ant colonies in South American jungles. This army ant killed by bursting out and swarming over the AA colony chewing up any resistance and carrying away the carcasses to feed their colony.
This underground army would kill and carry off the whole AA colony rather quickly. Great, I visualized a classical biological control project which would involve a personal 30 year effort. Such a project would require an impossibly big budget, a big quarantined warehouse holding colonies of the Argentine ant as a food supply for an army ant colony. Then the army ant would require assurances that it would be specific to the argentine ant, another unrealistic assumption. These sort of things are part of the necessary testing for a quarantine process to bring any natural enemy to theUS. This concept would require an enormous effort, almost impossible, so I staggered back to think.
Later after further cogitation I realized the AA was a beneficial species as it turned great volumes of soil providing aeration, and preyed on numerous pests (and beneficials alike), including subterranean termites and native fire ants. So it was a mixed bag, a good and a bad bug. They come that way at times. So it pays to learn something in depth and not classify everything as a pest because someone else calls it a pest. Plus there may be other more logical and less risky natural enemies to consider. Thus consequently I worked on exclusion methods so people could keep the ant out of the jelly jar but keep them patrolling the house perimeter to eat termites, for example.
Carnivores Effective?
This question is critical in evaluating existing natural enemies found during monitoring. But if you can’t identify these organisms you may not realize they are being helpful. A classic case occurs with ladybeetle larvae which most people can’t identify so they only see the large aphid colony and treat it when the larval predator may be enough to suppress the aphid population below tolerance levels. The same goes for larval lacewings and the small Hemipteran predator in the genus Orius. These are generalist predators widely distributed across theU.S. with homologous species throughout the planetary terrestrial ecosystems.
Pictures of Orius, larvae or life cycle of lacewings and ladybeetles see CSPC
Orius Life Cycle
Enlarged Adult Orius (line drawings), photographs of nymphs and adult.
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The Most Important Organism on the Earth are Not Humans
But the real prize goes for “crypticity” goes to the parasitoids. These are tiny “miniwasps” in the hymenopteran family Aphidiidae which look like winged ants to the lay person. These mostly selective species lay eggs in aphids with the ovipositor at the end of the abdomen.
Figure xx. An Ovipositing Miniwasp Attacking an Aphid Colony.
The egg laying behavior looks like a fencer dashing about thrusting a sword into the aphids. It’s fast and rather furious and can be most effective if the host and the parasitoid are well matched. I distinguish parasitoids from parasites even though specialists call these miniwasps by both terms. The proper term is “parasitoid”. To make matters worst there are similar species which attack the primary parasitoids which are called hyperparasitoids. See Figure z.
Figure z. A Primary Parasitology Emerged from this Dead Aphid.
(Primaries have even round emergence holes, secondaries have irregular edges on their emergence holes.
A parasitoid is really a highly specialized predator, but does not work like a ladybeetle, for example. Common predators, like the domestic cat, kill and eat a wide range of organism, mice, birds, lizards, insects, bats, snakes and others. Parasitoids are like parasites living inside the pest, but kill the host which many parasites only weaken over a life time. Their restricted host ranges make them very different from most predators which consume their prey in one meal, usually (see Figure x.)
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Figure x. Life Stages of an Aphid Parasitoid.
From UC,Daviswebsite.
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The parasitoid egg hatches inside the aphid and kills the aphid by eating the insides out, then forms the remaining aphid skin into a shell like aphid with color changes ranging from black and tan. It looks like a swollen aphid and is frequently found off the leaf, which makes it even harder to evaluate the effects of predation. Aphid dissections are needed but even these are subject to error as the eggs are difficult to see.
To really determine if this sort of natural enemy group will be enough to reduce a developing aphid population requires experience and some detailed examination, frequently calculating percentages, e.g.,2 lady beetle larvae/30 aphids/leaf, and 5 mummies/25 aphids/leaf. With this sort of measurement and a few monitoring visits one can guess at what levels of natural enemies can be effective. Looking one time and spraying is rarely a good idea.
A good rule of thumb is to count the number of ladybeetle egg masses while also counting the aphids. This is simple because adult ladybeetles need the protein from the aphids to make their eggs. And the adult ladybeetle needs to eat many aphids to generate an egg mass, so their presence and their eggs means many aphids have already died. And then one can expect both adults and the hatched larvae to continue eating aphids with the combination being even more effective. When the adults are no longer seen they have eaten all they can, water washing will not kill the larvae, nor the adults but many aphids will die from broken bodies. Larvae and adult predators washed from plants are not killed and those aphids washed to the ground will be eaten by ants and other ground predators.
The next level up in human induced mortality is the use of soap solutions, or alternately alcohol or even ammonia solutions. The context for moving up in “Cide intensity” deserves further discussion. Higher intensity sprays will kill more aphids than water washing and even soap solutions but also natural enemies present in and around the colony. More conventional insecticides have greater residual lives and will kill for longer periods. This may be convenient but leads to resistance, and further outbreaks of aphids. Before long one joins the pesticide treadmill, something “cide sellers” love. You then become hooked like an addict to methamphetamines.
Control Feasible?
So let’s assume for argument that the carnivores are not effective because the leaves are lost from the roses, or the numbers of aphids on the buds prevent normal flowering.
A selective mortality agent like water washing is best for most situations, particularly as a first response. This tactic can leave enough prey to sustain the predator community which in the long run can keep the aphids under control. That’s the goal.
But something important should be added here for emphasis. If, for example, it takes 3 water washings to manage this aphid over a season, compared to the use of a single toxic insecticide like an organophosphate, carbamate, pyrethroid or the newer systemics, I would rather use the water. Water does not hurt anything else and is even vital for plant growth. How many water washings it will take to manage the situation then remains the unknown assessment. Each manager then needs to make a decision about what to do next.
The Treatment Sieve
I like to line up my potential treatment strategies and tactics in the form of a series of mental sieves. Table 1 lists the strategies and tactics from a rather broad range of possibilities which can be assembled into this mental sieve system. This compilation is regularly re-conceptualize to keep a mental listing as large as possible. For example, I just started evaluating the use of vinegar solutions for killing weeds in pavement cracks. This looks like a great, cheap, weed control tool analogous to water washing aphids. Hot water may also be useful.
Conceptualize this sorting device as a stacked series of sieves each with a decreasing sized mesh screen, each representing a treatment. The top sieve has a large mesh and each subsequent screen below the other has a mesh of decreasing sizes. Think about pouring the pest problem into the top sieve and if that treatment doesn’t solve the problem completely the problem drops down to the next screen. Ideally this series of treatment sieves can solve all pest problems.
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Table 1. A Summary of the Strategies and Tactics Useful in UrbanRoseGardens.
Strategy Tactic
Chemical Control Soap solution
Pyrethrin Insecticide
Biological Control Importation of Natural Enemies (NE)
Augmentation of Existing NEs
Innoculation of Lab Reared Native NE
Conservation of NEs
Physical Control Habitat Destruction: Cut Overwintering Canes
Pruning or hand picking
Water washing
Traping
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This sieve idea mimics the way mortality agents work on a pest problem. (SeeHagen’s survivorship curve with its natural enemy notations.) Consider as a first example in the first sieve water washing, the next sieve could be soap solutions. Commercial soap products are better than homemade solutions for they have a standard dose while home solutions must be rigorously formulated, chemistry students could easily do it, however. Homemade solutions, unless carefully prepared can vary and make observations confused. The next sieve could be alcohol solutions, next ammonia solutions (homemade), and last pyrethrin insecticide applications (commercial products).
The more toxic soaps, alcohol, ammonia and pyrethrin solutions will kill all natural enemies by contact, with the last being the most toxic. I recommend the pyrethrin solution as a last resort because it is highly effective but has a short residual life, maybe a few hours or one day, so it will not continue to kill everything that comes in contact with the plant surfaces. Ultraviolet light degrades this insecticide rapidly.
Figure y. Generalizable Survivorshop Curve Illustrating how and where various Mortality Agents Operate. (fromHagen, source unknown, in fact the drawing is temporitly lost and I may have to create a new one).
Biological Control (BC) Feasible?
I placed this strategy last because it is the most powerful means for pest control if it is the classical form. But it is the most complex. The classical form means importation of natural enemies from native areas from which the pest originated. Other types of BC, are augmentation efforts to inoculate or inundate natural occurring enemies. A whole range of these generalist predators and parasites are available from insectaries who raise them for purchase (see Rincon.com, for example.
Classical BC: Importation of Natural Enemies.
This tactic is the most powerful pest control method because it can lead to permanent pest control. Hundreds of examples proving this practice have been documented since the first major success which saved the citrus industry in California around the turn of the 20 century. The scale ladybeetle predator, Crytolaemus montrouzeri, was introduced from Australia to California stopped the scale from killing citrus trees, and that’s why we still have oranges for sale in North America. And it is also why California leads the nation in doing this sort of work.
Crytolaemus montrouzeri, the Mealybug Destroyer that saved the California Citrus Industry from the invaded Cottony Cushion Scale.
The classical approach however, needs very specific support systems, particularly people trained in this special science. It is however, still an art as the science remains poorly developed, practiced by few entomologists mostly under the tight control of the federal government and underfunded compared to the threats posed by introduced pests. Such specialists travel the world, make international agreements with colleagues in many countries and collect organisms for passage to quantine labs managed by University or USDA workers, under permits and tight controls to eliminate hyperparasites and other foreign treats. In addition, such collections must be precisely identified by taxonomists who are familiar with these organisms backed up by adequate museum specimens.
Figure Z. Trioxys curvicaudus attacking the Linden Aphid, Euceraphis tiliae, introduced successfully inBerkeley,CA.
My knowledge comes from successful projects against a series of shade tree aphids in the San Francisco Bay Area. These occurred on Linden, Elm and Tulip Tree aphids, each aphid specific to those tree species, and each involving highly specific parasitoids (see Table 2), imported from Europe and the East coast of North America. This work was done under the supervision of my old boss, a colorful advocate and anti-pesticide pundit of worldwide importance, Robert van den Bosch. Van, as he was called would travel the world each year and send back species he knew were going to be effective. So his decades of experience was what I relied on for our projects.
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Table 2. Successfully Established Shade Tree Parasitoids in theSan FranciscoBayArea.
Parasitoid Aphid Tree
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Trioxys curvicaudus Eucallipterus tiliae Tilia spp.
Aphidius hortorum Tinocallis platani Ulmus spp.
Aphidius liriodendron Illinoia (Macrosiphum) Liriodendron
liriodendron
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He used the unique identification aphid specialist, Hille Ris Lambers, a Dutch scientist funded by that government. Peter Stary, a Czeck, and MacKauer, a Canadian, both identified the parasitoids, the former for the parasitoids in the family Aphidiidae which only were known from aphids, and the later for Aphelinidae, which are narrow range scale and aphid parasitoids already well known as important natural enemies from many successful colonization’s in North America and elsewhere. The 2-3,000 specimens derived from my aphid/parasitoid studies were recently deposited at the California Academy of Sciences in San Francisco,CA.
I believe the loss of van, Lambers, by human life cycle limits and by now MacKauer, along with the other members of the Division of Biologcial Control, Ken Hagen, Huffaker, and Messenger, all deceased, and now the actual laboratories they used at the Gill Tract, in Albany, CA means those days and the successful projects they conducted will not be replaced. Maybe the dissolution of their laboratories and the lack of substitute scientists means the pesticide forces have won another victory in their projects to contaminate the earth.
It was always an uphill battle for funds, recognition and repulsion of numerous attacks from the pro-pesticide forces, so obvious even earlier against Rachel Carson, that the idea of biological control survived the pesticide era. Now Biological control appears greatly diminished when the planet needs this approach even more than in those days when we were active.
The rose pest managers, especially those who become IPM specialists will no doubt learn how important the classical approach is needed. This is because to manage an invaded pest requires considerable work. Successful classical BC projects do not require further efforts. It’s what a lay person would call magic, but the specialist knows it takes special knowledge and repeated work.
Table 3. List of Known Natural Enemies of the Rose Aphid.
Back in the 1970s I was interested in taking what we learned with our few successes with parasitoid reestablishment and organize a nation wide effort to set up IPM programs, particularly classical BC for the Shade Tree Pests of theUS. To do this one needs to know the full range of species which are known to attack the known herbivores which attack the shade trees. With funding from the EPA we compiled over a six year period a searchable database of 5,000 species. This was based on over 900 catalogues, papers, and indexes. Three to four people labored for about 6 years to compile this source.
The data from this source provides the list in Table 3 for the rose aphid. This was a demonstration project stimulated by our project officer at EPA at that time, Darwin Wright. A summary of the structure of this database is presented in Diagram x, below.
Diagram X. The Structure of The Database of the Natural Enemies of The Shade Tree Pests of theUS.
Table 3. A listing of the Natural Enemies of the Rose Aphid, Macrosiphum rosae from Olkowski et al. 1976?. Database printouts available on www.WHO1615.com.
Carnivore One (means a primary carnivore), abbreviated CARN1.
Parasitoids, abbreviated PARA1
Aphelinus asychis
Aphelinus gossypii
Aphelinus howardii
Aphelinus sp.
Aphidius alius
Aphidius chilensis
Aphidius confuses
Aphidius ervi
Aphidius nigripes
Aphidius rosae
Charips luteicornis
Chrysolampus thenae
Ephedrus californicus
Ephedrus incompletus
Ephedrus lacertosus
Ephedurs plagiator
Ephedrus sp.
Euaphidius cingulatus
Lysiphlebus sp.
Lysiphlebus testaceipes
Praon aguti
Praon occidentale
Praon rosaecolum
Praon simulans
Praon unicus
Praon volucre
Predators
Pribremia aphidophaga
Adalia biopunctata
Adalia decempunctata
Adalia revelieri
Adonia variegate
Allograpta exotica
Allothrombium fuliginosus
Anthocoris pilosus
Aphidoletes aphidimyza
Aphidoletes aphidovora
Austromicromus tasmaniae
Calvia decimguttata
Calvia guatuordecimguttata
Carposcalis
Chrysopa abbreviate
Chrysopa carnea
Chrysopa perla
Chrysopa septempunctata
Cocconella ancoralis
Coccinella conglobata
Coccinella quadripunctata
Coccinella quatuordecimpustulata
Coccinella repanda
Coccinella septempunctata
Coelophora inaequalis
Cycloneda sanguinea
Eriopis connexa
Eumicromus angulatus
Hippodamia convergens
Hyperaspis festiva
Isobremia keifferi
Leis conformis
Melangyna viridicesps
Mesograpta watsoni
Nabis pseudoferus
Pemphredon lethifer
Pemphredon lugubris
Phaenobremia
Platychirus
Propylaea sp.
Psenulus pallipes
Scaeva melanostoma
Scaeva pyrastri
Scymnus subvillosus
Scymnus (Stethorus) sp.
Semiadalia undecimnotata
Simosyrphus grandicornis
Sphaerophoria javan
Spaerophoria ruppelli
Sphaerophoria scripta
Syrphus balteaus
Syrphus corollae
Syrphus latifasciatus
Syrphus nitens
Syrphus ribesii
Syrphus serarius
Syrphus citripennis
Thea vigintiduopunctata
Evaluation of Potential Importation Species
I tackle this subject last, because it is by default, or sometimes deliberately the last tactic when nothing works to prevent intolerable damage. It is certainly the most complex. This tactic is something to explore when the water washes fail and even those methods along the gradient to insecticides fail, and the plant still suffers intolerable damage and maybe dies from pest attack. Some of the exotic plants should die, because the damage done by them and their pests to our native ecosystems will persist forever. That approach is used against weeds, for example. Alternately, while water washes and other insecticides may provide temporary relief the possibility of importing certain natural enemies can be evaluated while holding the aphid at bay, so to speak.
But invaded pests like Cryphonectria parasitica, the causal fungal pathogen of Chestnut Blight (see Box ZZ below), which killed off our most beautiful native chestnut trees and now other examples of invaded pathogens, tell such stories. Although there are possible solutions for these type projects they remain relatively unexplored, certainly as potential classic BC cases, even thought natural enemies are known from native areas. For plant pathogens viruses and other fungi are known to attack many bacterial and fungal pathogens of plants, but this area remains poorly explored as are those for many other animals, including many crustaceans, fishes, mollusks, and birds for example.
Chestnut blight
From Wikipedia, the free encyclopedia
|
Chestnut blight fungus |
|
|
Cankers caused by the fungal infection cause the bark to split. |
|
| Kingdom: | Fungi |
| Phylum: | Ascomycota |
| Subphylum: | Pezizomycotina |
| Class: | Sordariomycetes |
| Order: | Diaporthales |
| Family: | Cryphonectriaceae |
| Genus: | Cryphonectria |
| Species: | C. parasitica |
The pathogenic fungus Cryphonectria parasitica (formerly Endothia parasitica) is a member of the ascomycota (sac fungus) category, and is the main cause of chestnut blight, a devastating disease of the American chestnut tree that caused a mass extinction in the early 1900s of this once plentiful tree from its historic range in the eastern United States.
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One way to simplify the evaluation process is to first exclude predators, because they may if established interfere with the natural enemies of other stable ecosystems. This is a general assumption borne from cases where vertebrates were introduced like the mongoose, who were deliberately introduced to many islands in the Pacific. The mongoose was introduced to control rats which were brought to the islands by traders and military personnel ignorant of the consequences.
The consequences included destruction of many native, rare and special highly specific species which had evolved to survive on these isolated places directly by rat predation, but also by the rat destroying many native predators, like snakes, and other wildlife, like native birds. Importing predators is a secondary possibility in some cases but in this case it is not necessary as there are parasitoid possibilities which promise more specificity.
The list of natural enemies of the rose aphid above once predators are excluded needs to viewed further in two ways: 1) Possible Native Importations: this involves potential targets for importation from areas wherever they occur in the US. This is because it is possible that a natural enemy inside the US could be useful in another area of the US where it does not now occur. This is what we did with the tulip tree aphid importation project mentioned in Table 3. We found specific miniwasps on the east coast and introduced it to the San Francisco Bay Area with good results.
But the best targets are foreign areas where the aphid is under better control than here in theUSwhere the aphid is exotic. This fits most pest problems faced by agriculture and horticulture.
So the other option needs to be considered in reviewing the literature: 2) Classical Importation. This type project is more complicated because it involves searches in foreign countries where the cultures are different as are the languages and travel considerations may become paramount. Shipments to the US must be brought to an airfield for transport to a quarantine lab in the US, which at that time were only four, two in CA, another in New York, another was in Hawaii. There might have been others but those were the only ones I knew about then. The lab in northern California was in the laboratories at the Gill Tract in Albany,CA, the city next to Berkeley near my laboratory.
Assuming one has the right permits the real job of finding the potential species for importation is tricky because one must search at a time in the season when the natural enemy occurs in sufficient numbers to be worth the labor of collecting and preparing the specimens and then getting to the airport quickly. That scenario is best for matching the seasonal patterns between the foreign area and the importation area. Then the potential colonization areas need to be protected against insecticide applications. This is also tricky as unsprayed colonization areas are needed.
If the pest was being regularly treated with insecticides for decades as was our experience with our shade tree pests listed above the pest population will soar well beyond the toleration zone. We may have been successful largely because we controlled the pest management programs in the cities we worked in. See our website for further detailed reports (www.WHO1615, under Science, then under IPM, then selectBerkeley,Palo Alto andSan Jose). There are over 50 annual reports for the 6 cities we worked with before Proposition 13 cut off funds to the cities which resulted in drastic cutting of shade tree programs, and incidentally but fortunately the pesticide treatment programs.
Quarantine Labs are Not Common
The quarantine laboratory takes out any hyperparasites attacking the primary parasites. Ideally the new species should be passed through one generation of the target pest. This requires a colony which either is being raised in the laboratory behind closed doors and isolated from the environment to prevent accidental escapes, or raised outside the lab in another lab with regular passage of living material into the laboratory. By raising the new species on its target pest one gets a first test to see if the new natural enemy will attack the pest.
Our early experiences with the silver maple aphid parasitoid, which is also a widespread pest of shade trees in the Central Valley of California showed that the parasitoid did attack the aphid but did not develop further and no adult emergence occurred. This meant that the match between the pest aphid and the new potential natural enemy was off someway. It could be due to misidentifications of the aphid, or the natural enemy. And then there is an incompatibility due to unknown factors generally called ecotype mismatch.
This assessment refers to a sort of ecological effect which has selected the natural enemy from an aphid variety very different from that which is occurring in the pest area. This was the end of the efforts we made to import against this pest inCalifornia. Someone else could pick this project up at some future time now that new genetic methods can assure precise identifications. The ecotype question then could also be surmounted as ecological fit can be assured.
Next in the evaluation process is host specificity. This requires research and should first be approached by examination of the literature. The ideal is a host specific parasitoid as these will ride the pest population down and not switch to another aphid as is the case with the polyphagous predators. Parasitoids come in three flavors: mono-, oligo- and polyphagous. The term polyphagous applied to a parasitoid is slightly different from the same term applied to a predator. Lacewings, for example, will feed on mites, Lepidoptera eggs, caterpillars of many species, aphids, mealy bugs and almost anything that moves, and they may even bite people.
A polyphagous parasitoid like Aphidius nigripes attacks many aphid species. Aphidius rosae looks like a good prospect as Stary (1970, p. 200) lists it as only attacking two species, the rose aphid, and Macrosiphum funestrum. Since both hosts are in the same genus this parasitoid may be a good candidate. Monophagous parasitoids are rare but have the greatest potential for complete biological control. Trioxys curvicaudus cited above is a good example. There are many species of oligophagous parasitoids and these may be good candidates but may require more than one species to be most effective.
Tell Conclusions to the Manager and Clientele
I mention this tactic as a final thought as part of the algorithm because it is the responsibility of the scientist, especially the specialist who can get lost in his/her own world to remember to keep the surrounding personnel acquainted with the status of any project, be it research, or applied biological control because many people are usually involved in these programs and their activities must be coordinated. We have been surprised at times by people who assume they know what is happening and want to help out by controlling a pest problem when no such control was needed nor warranted. Prevention is worth more than a pound of cure.
DIAGRAM OF SOCIO-POLITICAL BODY
Our seemingly endless efforts to educate the public and plant managers in many areas of North America and elsewhere through our publications, must be repeated by the minority of entomologists interested in bringing about a less toxic world. The public does not know of these options, nor their complexity and wants fast, simple solutions. Alas, there are no such things in managing parts of the natural world. Further, by demanding spotless plants and by continuing to buy toxic materials the status quo continues and that has been unsuccessful.
Bibliography
Beales, P. 1992. Roses, An Illustrated Encyclopaedia and Grower’s Handbook of Species Roses, Old Roses and Modern Roses, Shrub Roses and Climbers. Henry Holt and Company, NY.472 pp.
Minks, A.K. and P. Harrewijn. 1988. Aphids, Their Biology, Natural Enemies and Control, Volume B. Elsevier,Amsterdam. 364 pp.
Palmer, M. 1952. Aphids of the Rocky Mountain Region. Thomas Say Foundation, Volume 5. 452 pp.
Essig, E. O. 1929. Insects ofWestern North America. MacMillan Co., N.Y., 1035 pp.
Hill, D.S. and J.D. Hill. 1994. Timber Press,Portland,OR. 635 pp.
Stary. P. 1970. Biology of Aphid Parasites (Hymenoptera: Aphidiidae, with Respect to Integrated Control. Dr. W. Junk, N.V., TheHague. 643 pp.
Olkowski et al
Olkowski, W., L. Laub, A. Fedanzo, and ?
Zuparko, R. 1982.
Olkowski, W. Unpublished (see website for articles).
Quezada, J.R. and P. DeBach. 1973. Bioecological and Population Studies of the Cottony-cushion Scale, Icerya purchase Mask., and Its Natural Enemies, Rodolia cardinalis Mul. And Cryptochaetum iceryae Will., inSouthern California. Hilgardia 41 (10): 631-688.
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