nematodes are pretty tough and can survive the 

 pressures encountered in normal hydraulic sprayers. 

 (Note that they do NOT survive the very high pres- 

 sures - 2,000 psi which are being used in some turf 

 applications!) 



The nematodes have looked quite promising 

 against black vine weevils in nursery settings, par- 

 ticularly in the Pacific Northwest. Other researchers 

 have looked at their effectiveness against fungus 

 gnats, but these trials have been inconclusive. In 

 some cases they appeared to work very well, while 

 in other cases they have been much less effective. 

 There appears to be some evidence that potting 

 mixes or field conditions which contain relatively 

 high amounts of pine bark may interfere with the 

 effectiveness of the nematodes. In any case the 

 application procedure would be similar to that for 

 BT (i.e., three applications at five to seven day 

 intervals). 



One other kind of biological control which de- 

 serves mentioning is the use of insect growth regu- 

 lators. Insects go through a series of molts as they 

 mature from eggs to adults. Each molt is governed 

 by a series of hormones. One of these hormones is 

 a "juvenile hormone". As long as this juvenile hor- 

 mone is present, the insect will not molt to the 

 adult stage. In many insects this hormone is quite 

 specific. Scientists have identified the chemical 

 structure of this hormone for some insects. As it 

 turns out, if the hormone is then produced in the 

 laboratory and sprayed on plants, the insect believes 

 that the hormone is present in its own system and 

 will not molt to the adult stage. As a result it will 

 not mate and lay eggs to start another generation. 



Some of these juvenile hormones have been de- 

 veloped commercially. Enstar™ is a mimic of a ju- 

 venile hormone which affects the development of 

 whiteflies and some closely related insects. The 

 beauty of this approach is that Enstar™ is specific 

 to whiteflies and will not harm any beneficial in- 

 sects (such as parasites or predators) which might 

 be in the greenhouse. Equally importantly, materials 

 like Enstar™ are much less toxic to the applicator 

 and to employees who might have to work in a 

 treated area shortly after application than are most 

 traditional insecticides. 



Another kind of insect growth regulator interferes 

 with the molting process by blocking the produc- 

 tion of necessary proteins and other products 

 needed during the process. Azadirachtin is an ex- 

 tract from the neem tree, which grows primarily in 

 India. This material interferes with the molting pro- 

 cess of several kinds of insects, including whiteflies 

 and leafminers. Neem also appears to have some 

 "anti-feedant" characteristics to it. In other words, 

 it makes treated plants unattractive to some in- 

 sects. 



Neem is available commercially as Margosan- 

 OIM and as BioNeem™, and is labelled for use on a 

 variety of crops against several kinds of insects. 

 While it will affect more kinds of insects than will 

 IGRs like Enstar™, it is still much less toxic to hu- 

 mans and other vertebrates than most traditional 



insecticides. Current laboratory studies are looking 

 at combining neem with a "synergist - a chemical 

 which is not insect-active by itself, but makes 

 neem much more active when mixed together. 

 However, some of these combinations are very phy- 

 totoxic, and so are not appropriate for use in any 

 market, particularly the ornamentals market. 



Meanwhile some companies are working on de- 

 veloping fungi which attack insects. Some of these 

 fungi have been released commercially in past 

 years. For example, Veiticillium lecanii was devel- 

 oped for use against aphids and whiteflies, particu- 

 larly in Europe, and was marketed in the United 

 States briefly as Vertilec™. The main drawback was 

 that the fungus was only effective when relative 

 humidity remained quite high, and under these con- 

 ditions Botrytis and similar fungal diseases tended 

 to thrive. 



Current research is centered on fungi which are a 

 little less sensitive to humidity. Commercial re- 

 leases are still a few years away, but some of the 

 fungi show considerable potential for controlling 

 pest insects. 



The use of biological control agents is increasing in 

 many crop settings. In some cases these agents are 

 a bit trickier to use than traditional insecticides, 

 because storage or handling of the biological agents 

 might be a bit more complicated or because timing 

 of application has to be more precise. However, sev- 

 eral such agents are showing considerable potential 

 to control pest populations and reduce the overall 

 pesticide load. 



Greenhouse and nursery managers should experi- 

 ment with some of these agents and become famil- 

 iar with the best way to use them. If they are used 

 properly (applied at proper intervals and directed 

 against the right stage of insect), they can become 

 valuable partners in an insect management program. 



Dr. Patrician J. Vittum is a memhei of the 

 Depaitment of Entomology, University of 

 Massachusetts, Amherst. Her address is Fernald 

 Hall, Amherst, MA 01003. The phone numbers at 

 the Department of Entomology are (413) 545-2283 

 and 545-2004. >* 



Garden Center 



TEL 625-8298 / fax 622-4073 



Greenhouses Nursery Craft & Christmas Shop 

 656 So. Mammonth Rd. (Rte.28A) 

 Manchester, NH 03103 



We wish all of you a prosperous 1993 



THE PlANTSMAN 



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