(continued from previous page) 

 were heavy and contained impurities 

 which caused plant injury. Modem oils 

 are lighter, purer, can be used all year 

 long and are much less likely to injure 

 plants. Still, horticultural oils like any 

 pesticide should be tested on a few 

 plants first, especially in hot weather. 

 Oils tend to kill insects predominately 

 by suffocation and are most effective 

 against eggs and juveniles of mites, 

 aphids, scales, and mealybugs. Neem 

 (Margsan) is a seed extract which is 

 new to the marketplace and not yet 

 registered in New Hampshire. It has 

 been effective against greenhouse 

 leafminers and further uses are being 

 developed. Abamectin (Avid) is a 

 macrocyclic lactone that is labelled for 

 mite control but also effective on many 

 other insects. 



Resistant Plants: 

 Many varieties of plants are natu- 

 rally resistant to certain insects. Grow- 



ers and landscapers should encourage 

 the consumer to buy resistant varieties. 

 Unfortunately this is easier said than 

 done asconsumer preferences are often 

 dictated by physiological traits and 

 cosmetic appearances. As long as pes- 

 ticides are still relatively cheap and 

 easy to apply, there is little incentive to 

 change. However, as environmental 

 concern increases, consumers will 

 demand low maintenance plants. 



Monitoring and Mechanical Control: 



Not enough use of yellow sticky 

 boards occurs in New Hampshire. The 

 insect is attracted to the yellow board 

 and is trapped by a sticky substance. 

 You must determine ifits worth making 

 the boards yourself or buying them. 

 The boards will attract aphids, 

 whiteflies, thrips, and fungus gnats. The 

 boards don't have to be large, but should 

 be 2-4 inches above the plant height. 

 One trap placed every 30 square feet 



will reduce insect populations consid- 

 erably. If traps are used just to monitor 

 insect populations, fewer are needed. 

 Traps should be checked at least once a 

 week. Chemical controls should be 

 applied when damaging insects first 

 appear as it is far easier to control in- 

 sects when populations are low. The 

 most common error growers make is to 

 wait too long to initiate control . Once an 

 insectpopulationhaserupted,conU-oIis 

 difficult even with chemical pesticides. 



Dr. Swier is an Extension Specialist in 

 Entomology, for further information on 

 IPM, you can write Dr. Stanley Swier, 

 Nesmith Hall, UNH, Durham, NH 

 03824, or call him at (603-862-1159. 



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