New Weapons in the Insect Wars: Developments & Discoveries in Biocontrol
by Robert Gerard, Second of Two Parts
April 2005, Acres U.S.A.

   Last month’s installment introduced the crucial work of Dr. Joe Ellington and the Biological Control Task Force at New Mexico State University. We continue this month with more of Ellington’s research and discoveries in the realm of biologically correct insect pest control.

   A dramatic example of insect resistance to pesticides occurred in the pecan orchards of southern New Mexico. Over the course of some 30 years, local pecan growers had sprayed against aphids intensively with a vast variety of pesticides. At the time, they were raising cotton under the young pecan trees, and the honeydew produced by the aphids in the pecan trees dripped down and lowered the quality of the underlying crop. Over the years, these growers stepped up spraying regimes over large areas — a great recipe to develop a high level of insecticide resistance. About ten years ago this resistance indeed reached a crisis — no insecticide worked effectively on the aphid problem.
   About six years ago, these pecan growers approached Dr. Joe Ellington with this problem. He recalls, “We didn’t know what to do because we hadn’t worked on that problem, but we told them what we thought was logical: to quit spraying, release lacewings and lady beetles, and let the weeds grow to diversify the environment. The next year the problem was essentially gone. They have continued to do this over the years, and it has worked.”
   This experience with beneficial insects motivated these and other pecan growers to help start the Bio Control Laboratories (the Biological Control Task Force) at New Mexico State University. Their experience convinced them of the potential of beneficial insects.
   Ellington says that when he first came to the Mesilla Valley about 30 years ago, weeds were disked regularly. Now, he estimates that two-thirds of the pecans have weeds or some kind of cover crop under them. He sees the move to this way of farming and the development of individual interplanting systems in a positive light, but feels that it needs a strict scientific look.
   Ellington believes that rather the letting the weeds grow rampantly, as many growers do, it is much more effective to cut them and drive the beneficial insects up into the trees. If timed properly, this practice could have a big impact when black aphid populations are increasing in the spring and fall.
   Ellington has also worked on planting cover crops within pecan orchards. His program presently has very good data on some aspects of cover cropping in cotton and are trying to work out when to plant and cut the cover crops in pecan orchards to develop a functional relationship between the population of insects on the ground and in the trees. They believe that with this information, cover-crop cutting can be done to coincide with the inception of the pest population.
   Although alfalfa is a wonderful ground cover to attract beneficial insects, pecan growers do not favor it because its big crowns are often hard to work with. Young pecan trees, commonly planted in alfalfa fields, often have a hard time competing for nutrients and water with the big-rooted alfalfa plants.
   Small grains such as wheat and barley have worked well to attract beneficial insects to pecan orchards, as has hairy vetch. In the spring, when barley or wheat begins to leaf out, huge populations of aphids appear, and lady beetles arrive in huge numbers. These small grains don’t do as well when grown through the summer, however, because of shading. They are also susceptible to disease under flood irrigation when the weather is warm.
   These obstacles could be overcome if the right agronomic factors were combined with good entomological practices. Good pruning — to get sunshine under the canopy — will improve the outlook for cover crops. The increased light, melded with correct levels of nitrogen fertilization and prudent watering, would also have a direct effect on the black aphid populations. Small grains could be planted on ridges to reduce disease problems with flood irrigation.
   The goal of the entomologists at New Mexico State University is to identify a ground-cover regime that will inform farmers when to plant something, when to cut it, and what to expect in terms of results. In the search for ground covers, Ellington is looking for older, non-improved varieties that don’t have aphid resistance built into them. These susceptible varieties contain nectar that attracts lady beetles, lacewings and other beneficial insects. Ellington finds it ironic that these varieties, once discarded as obsolete, are now being sought out for their entomological benefits.
   Ellington mentions working with the Beneficial Blend Seed Mix, a mixture of 12 species of plants developed by Rincon-Vitova Insectaries in California. The idea is to have one plant bloom every month of the year for a constant population of beneficial insects. The blend has worked well in California, with its Mediterranean climate, but did less well in the cold winters of southern New Mexico. It also did not perform well under the fairly closed canopy of pecan orchards. Nevertheless, Ellington feels that the philosophy of “a bloom a month” has potential. He mentions that some of the California wineries have planted different ground covers, depending on their conditions. The development of this ground-cover system has allowed wineries to control insects such as the grape leafhopper without spraying. The lack of spraying has also had a significant impact on the mite population, a secondary pest that increases after insecticide use.
   Other, untested crops also show great potential as refuges and food sources for beneficial insects. Ellington wants to look at sunflowers — he has been in some sunflower fields in west Texas that are loaded with insects. Alyssum, which attracts a good population of beneficial insects, also interests him. He recalls seeing it planted every seventh row in vegetable fields near Monterrey, California.
   When introduced or migrating naturally into a cropping system, beneficial insects can have a significant impact on pest populations. They can also do the unexpected and migrate beyond the area for which they were destined, or they might react to the environment in an unusual fashion. Ellington tells of a large pecan grower who bought lady beetles in huge numbers over a number of years. One spring Ellington got a call from a farmer south of the large orchard who was wondering whether his neighbor had released any lady beetles that year. When Ellington said he didn’t think so, the farmer said that every time his neighbor to the north released them, many would migrate down to his farm — that year, he hadn’t seen any.
   Another example of unexpected results deals with the Asian lady beetle, which was very successful when introduced for pecan aphid control in orchards in the U.S. Southeast. When brought into the Southwestern United States and Northern Mexico, however, it was not nearly as effective. Ellington thinks perhaps not enough time has been allowed, as it takes about ten or 15 years to adapt and build up numbers. The low humidity of the area could also have been a problem in its establishment. Even though the Asian lady beetle has not done well in desert regions, it has spread through the more humid areas of Mexico and Central America all the way to the Panama Canal.
   Mexicans recognize the Asian lady beetle as a good aphid predator and raise huge colonies on grain moth eggs in the laboratory. The growers who buy this predator claim they are getting good results and are giving the laboratory repeat business.
   A final unexpected result is illustrated by the seven-spotted ladybeetle brought in from the Near East and released in New Jersey. One winter, a fellow entomologist found a group of these beetles languishing on a snow bank in the middle on winter. He gathered them up. Ellington accepted an offer of some of these beneficial insects. Another group was sent to Georgia.
   After Ellington released these insects, the Mesilla Valley had a particularly severe winter, and all of the seven-spotted lady beetles perished. They did survive in Georgia, however, and about five years later made their way across the country to the Southwest. Scientists in Arizona were afraid that these new immigrants would displace the native lady beetles, but Ellington was not particularly concerned about their impact on native populations. In the intervening years, they have remained in southern New Mexico in low numbers and have never caused any problems with the native lady beetle population.
   As mentioned previously, one of the biggest challenges to the success of beneficial insects is the continued spraying of insecticides. Often, farmers spray these chemicals because they want a quick fix and a feeling of security that the pest problem is being dealt with. However, the pesticide makes it difficult for releases of beneficial insects to become established and do their job properly, thus it is difficult to judge their effectiveness. Ellington mentions that he tries to get around this problem at least temporarily by releasing them in fields and areas where pesticides are not sprayed.
Ellington mentions successes with the elm leaf beetle and notes that the introduction of a parasite to control it probably worked because no insecticides are typically sprayed on elm trees. He wonders whether there would not be similar spectacular successes with the introduction of beneficial insects in cash crops if pesticides were taken out of the picture.
   The recovery of beneficial insect populations after spraying is largely dependent on migration from neighboring unsprayed areas. On the small cotton fields of the Mesilla Valley, recovery of beneficial insects is often quick. There, once a cotton crop is sprayed and the residue has worn off after a week or two, it is common to find the beneficial complex as good as before spraying. In Ellington’s mind, this shows there is a lot of beneficial insect migration back into the sprayed field from alfalfa and unsprayed areas.
   It is a different story in the large cotton fields of the San Joaquin Valley, where spraying covers huge areas and beneficial insect migration from unsprayed areas does not occur. Without the migration of beneficial insects from surrounding areas, these farms find themselves in a situation where they have little choice but to spray the pest insects for the rest of the season.
   Although Ellington says the presence of beneficial insects is a good sign that pest populations have a certain amount of control, to date there have been very few studies to quantify their effectiveness. To get an accurate count and begin to judge the effectiveness of beneficial insects is a time-consuming task. All the insects have to be vacuumed out of a section of a field, and they are hand counted. Statistical determinations then have to be made from the population to judge whether the beneficials are having a significant impact on pests. Once this is determined, a plan of action can then be formulated.
   An example of the need for such data deals lies in the tiny wasp Trichogramma, a species of which has been used to control cotton bollworm in places such as Australia, Turkmenistan and Mexico. Ellington mentions a trip he took to Turkmenistan, where the government claimed to control cotton bollworm with Trichogramma. When he landed in the cotton-growing area of this former Soviet republic, he saw about 20 spray planes on the tarmac. He asked why, if their biological control was so effective, did they have all these planes? They responded that they hadn’t used them in years. Instead of spraying, they raise Trichogramma in huge factories and regularly release massive numbers to control their bollworm problems.
   The problem that Ellington sees with these releases is a lack of evaluation to determine the level of control they are getting. The Trichogramma in the program are raised in the laboratory, and after a number of generations, they could become inbred and overly adapted to an artificial environment. Once released, there is no evaluation of whether these wasps are competing in the real world and doing their job effectively. The only way to do so is to collect data and figure percent parasitization and pest mortality from the releases.
   Another problem with the use of some beneficial insects is that it is often difficult to find the right species to control a specific pest insect. In the same host-specific Trichogramma, the taxonomy requires a great deal of expertise. In the United States, there are only a couple of people qualified to do the important work of identifying Trichgramma species.
   Ellington mentions how they once released the species Trichogramma pretiosum for control of pecan nut casebearer. Evaluations following the release showed that this species gave no control of the pest insect. Investigating the lack of pecan nut casebearer control, it was discovered that T. pretiosum was supposed to be used in field crops, not in pecan orchards.
   After this discovery, a Trichogramma species specific for pecan nut casebearer was picked up in the Dallas, Texas, area. When this species was released in the orchard, evaluations showed about 30 percent parasitization. To further increase the parasitization, a kariomone was added that excites the Trichogramma and makes them look harder for their hosts. When the kariomone was applied in the orchard, the parasitization went up to about 80 percent.
   It is easy to spray a field, but figuring out everything that affects insect populations is a lot more difficult. The lack of data about control by beneficial insects creates uncertainty among farmers and often leads them to apply “tried and true” pesticides that do little more than kill off beneficial insects and leave chemical-resistant pest insects.
   Getting appropriate data quickly to determine a plan of attack on a pest insect is not an insurmountable obstacle, however. New technologies are being developed that show great promise in expediting insect counts and determinations of beneficial insect effectiveness. Once these technologies are in place, it will be much easier for the entomologist to show the farmer quickly and exactly the effectiveness of beneficial insects.
   Dr. Jeffrey Drake, a NASA and USDA employee, is working at the Bio Control Laboratories to develop quicker ways to count and determine the species makeup of insect populations. Using a camera, he photographs insects that have been vacuumed out of sections of a field. Once the photographs are taken, they are then put in a computer, where the insects are separated into different species by analysis of their shape, size and color. When presented to the farmer, this population data will allow a better determination on whether to apply an insecticide or allow the beneficial insects to do their job.
   This technology cannot arrive quickly enough. Lack of efficacy data on the impact of beneficial insects on pest insect populations creates uncertainty among growers. Adding to this uncertainty is a biocontrol industry that Ellington feels is under-regulated and does not give enough guarantees on its products. He mentions that insectaries only guarantee the species and the number of insects that are being received. There are no regulations to guarantee the amount of control these beneficial insects will provide or that they are the correct species for the pest insect problem. There are no requirements to state that they have been grown under the right conditions of temperature and humidity or that they have not been kept for so long that they are no longer viable.
   Despite the present problems with the biocontrol industry, Ellington believes there is room for any entrepreneur who is interested in starting a well-run insectary. There is also potential for individuals or cooperatives to raise beneficial insects on their own.
   Biological control in greenhouses is another area of the beneficial insect business where there is great potential for entrepreneurs. There are huge greenhouses in Europe, and a Dutch company that has set up shop in Wilcox, Arizona, grows tomatoes with a very impressive system that has been developed over the past 50 years: insect control is basically preventative maintenance, and different areas are under control of individual workers. When a pest insect is seen by one of these workers, its presence is immediately reported to the supervisor. Beneficial insects are ordered and released in this artificial environment where everything is controlled, making it perfect for biological control methods.
   Farmers and growers worldwide are recognizing the crisis in insecticide resistance. In New Mexico, the problem became so serious that farmers donated money to fund a laboratory for beneficial insects at a public institution. The realization of the role that beneficial insects can play in the war on pest insects is once again taking wing. In the state’s coming legislative session, an appropriation will be made to fund operational expenses in biological control, putting the necessary regional aspect on the use of beneficial insects. The bill is being cosponsored by Dr. Ellington and the New Mexico Organic Commodity Commission and is backed by many conventional and organic grower groups because they know that it works.
   If the bill passes, it will put New Mexico on the cusp of a growing technology. With the help of insectaries, farmers can find new, more effective, and cheaper solutions to their pest problems. It is to be hoped that this technology will continue to grow in other parts of the country and the world. Truly, the potential of biological insects in pest insect control is limitless. All that is needed to approach this potential is a concern about the growing insecticide-resistance problem and a willingness to try the alternative of beneficial insects.

    Robert Gerard is a market gardener in Chaparral, New Mexico, and frequently writes on agricultural topics. He is the author of Gardening the Arid Land, a technical manual on dryland gardening. It is available from the author for $8.95 postpaid at 441 Paseo Real, Chaparral, New Mexico 88021.

    Bio Control Laboratories (the Biological Control Task Force) can be contacted at the Dept. of Entomology, Plant Pathology, and Weed Science, New Mexico State University, Box 30003, MSC 3BE, GW Thomas Hall, Room 221, College and Knox, Las Cruces, New Mexico 88003-8003, phone (505) 646-2037, fax (505) 646-8087, website <www.nmsu.edu/ biocontrol>.
   
    Dr. Joe Ellington can be contacted via e-mail at <joelling@ nmsu.edu>. Rincon-Vitova Insectaries can be contacted at P.O. Box 1555, Ventura, California 93002-1555, phone (805) 643-5407, toll-free 1-800-248-2847, fax (805) 643-6267, e-mail <bugnet@rinconvitova .com>, website <www.rinconvitova.com>.