Ornamental Plant Production Using IPM
By: Frank Melton and Sylvia Shives, Manatee County Extension
Introduction
Healthy plant growth on a normal schedule to meet quality standards is the basis for making money in the nursery business or having satisfied landscape customers. Integrated Pest Management (IPM) is a method of growing plants with minimum pesticide use and to delay pest resistance to pesticides. Some call it Plant Health Care or a similar term. Field demonstrations show some of the effective ways to implement an IPM program.
Some nursery owners tend to apply a pesticide at the first sign of a problem with their plants. Plants can be stunted or grow slower than they should because of environmental factors such as being planted too deep, over watering, media pH being too high, or over-fertilization. They may not necessarily have an insect or disease.
Healthy plants usually are resistant to pest damage, so first be sure to use proper growing practices. Some tests should be made of media pH and salts and irrigation water salts, pH, and alkalinity to be sure they are in the correct ranges for your plants, based on ABMP's for Container Woody Ornamental Production." High pH of spray water also destroys the usefulness of some pesticides.
The cornerstone of an IPM program is scouting or monitoring plants for insects, diseases, and other problems. When a problem is found, the question is whether the problem should be treated. That depends on how soon the plant will be sold, and how your customers accept the presence of beneficial insects on their plants. Normally, when plants are not to be sold for a month or more, beneficials can be used. Some nurserymen who have landscape contractors as customers, do not mind having beneficials on their plants. Beneficial mites are hard to see, and most people don't know they are present. Refer to this site's references on which pesticides are less toxic to beneficial insects that are naturally occurring or bought. Stronger pesticides vary in the time their residuals are harmful to beneficials. They may last one week or up to six months.
It is important when using beneficials to start using them at low pest populations (2-10%), so you may need to first spray a pesticide to bring a large population of pests under control. If you are having a hard time controlling a pest with pesticides, you may want to release a large number of beneficial organisms about a week after the last application of a compatible pesticide. Another alternative is to use pesticides that are more compatible with beneficials for a week or two before releasing beneficials. The next step is to try to control as many pests as possible with beneficials.
Control of spider mites, with which we have the most experience, works best when releases are made when populations are increasing but below 5%. At that time biological controls are our first option. Do not irrigate for 12-24 hours after beneficials are released. At the 2-10% level, biological controls have a good chance of succeeding, but a least toxic pesticide application may be necessary at above the 10% level. This depends on how patient you can afford to be with that crop. What is your threshold of tolerance? If you cannot afford much damage, you may want to apply a pesticide with less toxicity to beneficials at the 10% level to avoid applying a stronger pesticide later. Always use spot sprays if possible rather than full coverage sprays. When you must use pesticides, rotate them among various groups of common pesticides. Rotating chemicals among groups delays the buildup of resistance to pesticides. Sometimes pesticides do not control pests, and beneficial organisms work better.
It is important for growers to work with the scout and extension agent to follow any recommendation in a timely manner (within a day or two), because a higher pest population changes the recommendation that would be given. Also, the timing of pesticide recommendations needs to be done with the scout in mind. Remember that the scout needs to know what has been sprayed for their safety and to comply with the WPS laws. A scout should take the WPS Pesticide Handler Training just in case they have to scout before a re-entry time has passed. They are then required to wear a handler's personal protective equipment. It is best to coordinate sprays, so that the scout does not have to enter before a re-entry time has passed.
Also, be sure you learn what beneficials may be in your area so you don't spray primarily to control a beneficial. Anything you can do to reduce pesticide use and make the ones you do use most effective will be best for an IPM program.
Grower Experiences
We had six nurseries cooperating with us on this program. These experiences have worked, but they are not replicated experiments. Use of brand names does not mean it is a recommendation. One cooperating nursery had a problem with Florida red scale on Kentia palms. He sprayed Dimethoate once in the fall of 1997. He was using predator mites for twospotted mites nearby, and did not want to kill the predators every time he sprayed. S-kinoprene was the only chemical for scale that has been tested as relatively safe on beneficial insects and mites. S-kinoprene is an insect growth regulator that works slowly and best on crawlers, and it is recommended for several applications starting at a higher rate then reducing the rate. S-kinoprene was applied about a month after Dimethoate, and then five times after that. The adult population increased at the end of March. Aphytis holoxanthus is a wasp that lays its eggs in the Florida red scale, and the young develop inside the scale as they eat the live part of the scale under the armor. This parasite has been used on Florida red scale on citrus, so we obtained a few from Dr. Lance Osborne on a Dracaena marginata which had red scale and set it among the Kentia palms about April 15, 1998. About the same time, some twicestabbed lady beetles appeared from the surrounding area. It seemed that the wasps were killing the scale and the lady beetles were cleaning them off the leaves. The population was kept low for at least a year after that time with no pesticide application. I have seen a different wasp, that naturally occurred at another nursery, laying eggs in a Florida red scale.
Another nursery used minute pirate bugs on thrips on marigold flowers. Thrips were a problem on twenty-five percent of the marigolds when minute pirate bugs were released April 14, 1998. Within three weeks, thrips were a problem on less than five percent of the marigolds, and have stayed at that level or less for ten weeks.
The same grower had some pentas with spider mites. He made a release of predator mites when the population was low, but it was made a little late. Sometimes the grower delays and sometimes the problem might be with coordinating the shipment of predators. S-kinoprene was applied later for aphids. Population of mites later increased and predator mites were released. This grower has been a cooperator for three to four years, so he seems to have some predator mites around the nursery and various beneficials in the area surrounding his nursery. The scout is also a contract scout on four other nurseries which have been successful with an IPM program.
Another grower was unable to kill Florida wax scale on Indian Hawthorns with pesticides. We tried Metaphycus helvolus, which worked, Cryptolaemus montrouzieri (mealybug destroyer), and Rhyzobius (= Lindorus), a lady beetle. This is an example of a beneficial organism controlling a pest when a pesticide could not. The Cryptolaemus montrouzieri traveled 100 yards from where they were released to coontie, which had hemispherical scale. Also Cryptolaemus montrouzieri can be used on mealybug. Many other beneficials are naturally occurring. Several of the released insects and mites have reproduced and been available when another group of pests appeared later. The scout is also a contract scout on four other nurseries which have been successful with an IPM program.
Attracting Beneficials
Use a variety of flower types: Composite, umbels, cups, spikes, and have a variety of plants. Podocarpus is very good for attracting lady beetles to feed on podocarpus aphids. Crepe myrtle has a high number of beneficial species. One nursery has woods and citrus around it. Beneficials reproduce in the nursery or the woods and return to feed on pests.
Feeding (artificial diets): Some companies sell food mixes, pollen, proteins, and sugars. They can be sprayed on plants or boards mounted on a post. See the book Common Sense Pest Control by Olkowski, Darr and Olkowski.
Conclusions
The purpose of this information is to let people know about some IPM programs that have worked, but it is not replicated research. The pest management program that includes: proper basic horticultural practices, scouting, coordination between grower, scout and extension agent, use of pesticides less toxic to beneficial organisms and the release of beneficials has saved two growers about $5,000 per year on these crops. Another nurseryman has saved about $20,000 per year on their whole nursery.