GreenMethods.com
Alternative Pest Control at the Production Level 2

Alternative Pest Control at the Production Level: Biocontrols in the Real World

This installment is part two of a two part series.

Faced with the fact that the vast majority of foliage plant producers do not employ biocontrols or alternative pest control methods during the production cycle, the interiorscaper who strives to reduce the use of chemical pesticides on plants used in interior plantscapes is faced with a dilemma: how can I institute an alternative pest control program on plants that have been raised using significant quantities of chemical pesticides throughout their production?

Obviously, the issue of pesticide residues is the first hurdle to be overcome. Plants received from growers or distributors undoubtedly will contain the remains of pesticides applied from the time they were cuttings or tissue culture transplants at the nursery and continuing throughout the production phase, up to and including the shipping process. Prior to introducing living predator or parasite insects or mites onto these plants, residues must be reduced to tolerable levels, which differ for each beneficial organism. Washing foliage may remove some water-soluble residues, but there is the problem of adjuvants, chemicals added to pesticide applications to enhance the efficacy of the pesticide by making it disperse more evenly and completely on the plant’s leaf surfaces (”spreaders”, which break the surface tension of the spray droplets and cause the spray solution to coat the leaf surfaces uniformly and thoroughly), or by causing the spray solution to adhere tightly to the foliage long after it dries, so that it does not wash off when rain or overhead irrigation occurs after application (”stickers”).

These aid in the efficiency of the chemical spray application, but they also make the residues much harder to remove. In a study done by the Connecticut Agricultural Experiment Station on removal of pesticide residues from produce, rinsing with tap water for at least 30 seconds produced very mixed results in the removal of certain pesticides to a level considered safe for human consumption, while the use of commercial sprays designed to remove such residues was no better than tap water, nor was the use of detergent sprays. Human tolerances for pesticide residues are probably much higher than would be the tolerance of arthropods like insects and mites, mainly due to our vastly larger body mass, so the prospects for getting foliage plants clean enough to support populations of introduced beneficials would seem pretty dim, barring some extraordinary processes that would remove significantly more residue than rinsing with water does. Not an encouraging finding.

So if the interiorscaper does manage to get the target plants clean enough to possibly support introduced beneficials, the next problem becomes sourcing a reliable supply of the intended predator or parasite. With the rising consciousness about alternative pest control today, there are many supply sources in the marketplace, from established insectaries to mail order gardening websites to commercial greenhouse supply companies to the spinner rack at the local garden center. I can testify to the fact that the vagaries of shipping conditions (time, temperature, packaging, quality of the source) will have a lot of influence on the success of any application of living beneficials. The organisms must start out with a high percentage of living, active specimens, because survival rates in transit can only cause shrinkage of useful numbers from that level. The onus then falls on the interiorscaper to make the application in a timely manner once the (hopefully) vigorous living organisms arrive from the insectary, before the numbers of active organisms drop below the levels required to achieve control on the target plants. Next is the issue of proper application techniques; each organism has its own preferences for temperature, humidity, food sources, etc., and failure to match the beneficial to the target pest and prevailing environmental conditions will almost certainly result in failure of the application. Finally, expectations must be reasonable: a population explosion of two-spotted mites in a hot, sunny, dry interiorscape is not going to be beaten back by an application of predator mites, and disappointment will be the only result.

As an interiorscaper who has used a number of different biocontrol resources in the interiorscape over the years, I am still skeptical about the prospects of one day shunning the use of chemical pesticides. When applied in a timely manner and under conditions that are close to optimal for their survival and successful activity, these organisms can be very useful in controlling some of the most difficult and intransigent pests in the commercial interior landscape. In fact, I have given an unqualified “two thumbs up” endorsement — in person, in print and online — to the use of beneficial nematodes (Steinernema spp.) for the control of fungus gnats in the interiorscape. A single application of these tiny worms is usually sufficient to break the life cycle of this vexing pest within a couple of weeks, and recurrences of the infestations are virtually unknown to me. That’s alternative pest control at its best!

Perhaps two real-world case studies from my own experience in the industry will demonstrate the pros and cons of using beneficials in the interiorscape.

First, the bad news: two-spotted/red spider mites are two of the most dreaded pests to confront the interiorscaper. Because many of the sites where we attempt to maintain foliage plants in attractive condition tend to be dimly lit, dry places, the plants themselves are often stressed to some degree the year round. This affords opportunistic pests like mites an ideal target for colonization and reproduction, and we battle infestations of these pests on certain crops on a recurring basis. Thin-leaved plants like palms and some dracaenas are highly susceptible to mite infestation, and because of their leafy, bushy habits of growth, spraying can be difficult to accomplish successfully. Compounding this difficulty is the unpopularity with clients of people wandering into their places of business wearing nitrile gloves and Tyvek rainsuits, carrying fearsome-looking spray equipment, much less actually using it!

So it was that our company found itself in the predicament of being custodians of several very large (20-foot-tall) specimens of Wodyetia bifurcata (Foxtail Palm) at a local airport terminal some years ago. The Foxtail Palm is a beautiful specimen native to the Australian archipelago that features long, dense plumes of lush foliage on the upper third of the tree. These three-dimensional fronds, for which the species is named, can have a decided downside during the maintenance phase: mites adore the foliage of this palm, and the density of the foliage makes effective spraying a virtual impossibility. Add to this the fact that the client would not authorize traditional spraying of these large specimens during times when the surrounding terminal areas were in use (read: 24/7/365), and that the palms could not be moved off site for treatment, and you have a classic situation that called for alternative pest control methodology.

I decided to try to make an application of predator mites, with which I had no prior experience. I contacted a local supplier for more guidance and was advised to try a blend of two species, Phytoseiulus persimilis and Neoseiulus californicus, the former noted for its quick knockdown capability, the latter for its ability to survive for long periods in the absence of prey, waiting for a reinfestation to occur (the equivalent of a “sleeper cell”). We deposited the mites and their carrier material, ground corncobs, in little hanging cardboard holders [distribution boxes] at the base of each frond, from which they would presumably crawl out and about, looking for prey. Several weeks later, the pest mite population had noticeably decreased, as noted by the absence of webbing and fewer pests moving about on the foliage. However, by six months after application, a new infestation had exploded, requiring a lot of ladder-climbing and hand-wiping of the foliage to remove as many of the pests as we could without spraying. The beneficials (or at least their activity) were nowhere in evidence. Since that time, we’ve never used predator mites again in the interiorscape, although we did have very good success in knocking down an infestation of two-spotted mites in a greenhouse monoculture of Pachira aquatica (”money tree”) some years later using these organisms. Given the right combination of low pest pressure and amenable environmental conditions, these predator mites can be an economical (and politically correct) tool in the interiorscaper’s arsenal of alternative pest controls.

The good news is that fungus gnats, which are the source of the vast majority of interiorscape client complaints, can be successfully managed, if not eliminated, using a group of minuscule roundworms referred to as beneficial nematodes. Of course, these critters don’t know they’re beneficial to anybody but themselves, because they are mindless, gnat-larvae-eating machines, but this is a happy circumstance for us interiorscapers who field inquiries from clients about these annoying pests year ’round. Fungus gnats are an especially common problem on plants shipped from Florida after prolonged periods of wet weather, and as a result we have taken to routinely applying pesticide drenches to the soil prior to installing any of these new arrivals at our interior accounts. If not, I can count on making a personal appearance within a few weeks of installation when the gnats begin to fly lazily and persistently in front of people’s faces, necessitating unpopular applications of pesticide drenches on site, with the accompanying trauma of notification forms and posting of pesticide warning signs throughout the account. Not something that most clients enjoy.

The only downside to using nematodes is that they do not control the existing population of flying, adult fungus gnats. But that’s a negligible flaw, because there is no chemical pesticide that can be legally applied in an interiorscape that will, making nematodes a much more palatable solution on the job. The two-week lag time required for the nematodes to eliminate the soil-borne gnat larvae before they become winged adult reproductives, and for the existing flying adults to live out their miserable lifespans and crash to earth dead, is a small price to pay for the resulting long-term, pesticide-free control in sensitive public spaces such as offices, hospitals, shopping malls and office buildings.

So while we interiorscapers will never be the standard-bearers for pesticide-free horticulture, neither are we Neanderthals in that regard. We realize the value of good public relations (i.e., that frequent applications of chemical pesticides are neither desirable for the environment nor good for business), and we can choose to use these tools in targeted, selected situations where they have the best chance at providing effective control of pest populations economically and safely. Integrated pest management, after all, does not require complete abstinence from the use of chemical pesticides. It does require the use of appropriate pest control techniques for each individual circumstance, and when conditions permit, beneficials can be the most appropriate choice for responsible, long-term control of certain pests in the interiorscape.

Missed Part I? Be sure to check out part one of Alternative Pest Control at the Production Level.

About the Author: Clem Cirelli, Jr. is the manager of Summit Plants and Flowers, Inc. of Belle Meade, New Jersey, and he’s been at it for more than twenty-five years. Mr. Cirelli used to also be a regular writer for Interiorscape Magazine. He is quite well-known in the interiorscape industry. Also see this grower interview.

Filed under Contributors, IPM Savvy —

Bookmarking Links » del.icio.us | Digg | StumbleUpon | Technorati | Help? |

Here’s more content that might be related:

Alternative Pest Control at the Production Level »

Natural Pest Control: What to Expect »