applied to the uninjured bark of the tree at the proper 

 time. It shows possibilities for providing a control 

 measure for the midge Oligotrophus sp., a troublesome 

 pest of ornamental junipers or red cedars, for which 

 there has been no satisfactory control. Experiments 

 indicate that SD-3562 is toxic to the bagworm and 

 mimosa webworm at lower dosages and over a much 

 longer period of time than it is to the European elm 

 bark beetle. 



One of the problems in the use of a systemic 

 insecticide is the selection of the proper method of 

 application. There are three general methods: the 

 chemical can be sprayed on the leaves of the plant, 

 it can be placed in the soil, or it can be placed in or 

 on the trunk of the plant. The first method, foliar 

 spraying, seems to offer the least advantage over 

 methods that use nonsystemic insecticides. Soil appli- 

 cations offer practical possibilities but, with such 

 variables as soil type and moisture, effective dosage 

 levels are difficult to establish. Then, too, a great 

 deal of the chemical is wasted in soil applications. 

 At this time, the introduction of the chemical through 

 the trunk into the sap stream of a tree commands a 

 great deal of interest because of the possibility of 

 obtaining quick, positive results with a small quantity 

 of chemical. 



Methods of treating trees with SD-3562 by means 

 of holes drilled into the trunk, or by other means that 

 make wounds in the trees, appear to be fundamentally 

 unsound. Small, thin-barked trees, such as honey 

 locust, react rather violently to wounds, especially 

 when the wounds are laved with the chemical, figs. 8 

 and 9. Accidental wounds or wounds made in the bark 

 by insects may be the foci of chemical injury. Such 

 injury is unacceptable if yearly treatments are neces- 

 sary, as, no doubt, they would be for control of most 

 tree pests. 



Although the method involving chemical appli- 

 cation to uninjured bark may not be effective on all 

 kinds of trees, such applications seem to be on a 

 sounder footing than methods requiring damage to the 

 bark. 



Coupled with its advantages, SD-3562 has some 

 drawbacks. Since the chemical is very poisonous and 

 since it is phytotoxic at some dosage levels, details 

 of handling, usage, and application, as well as dosage 

 levels for both pests and plants, must be worked out. 

 On the basis of our work, it appears that further re- 

 search is needed before we can recommend SD-3562 

 for use by the public. 



ABSTRACT 



Tests with technical grade SD-3562 injected into 

 elm trees in a nursery showed that this systemic 

 chemical, although effective at some dosages against 

 the smaller European elm bark beetle, the principal 

 vector of Dutch elm disease, presented the problem of 

 little margin between effective dosage to control 

 beetle penetrations and chemical injury to the trees. 



Field tests with SD-3562 injected into elms to 

 control Dutch elm disease, although encouraging, were 

 inconclusive and should be continued. Small elm trees 

 seemed more vulnerable to injury by the chemical than 

 large ones. 



Experiments with honey locust trees showed that, 

 after application of the chemical to the uninjured bark, 

 the trees were toxic to the bagworm, the mimosa web- 

 worm, the honey locust mite, and the fall webworm. 



SD-3562 was effective against the fall webworm 

 on oaks only when applied to injured bark or through 

 holes in the trunk; injury to the bark resulted. The 

 chemical apparently did not penetrate uninjured cak 

 bark as readily as uninjured honey locust bark. 



Diluted SD-3562 injected into soil around arborvitae 

 and Canaert red cedars provided excellent control of 

 bagworms and midges, respectively. Injected into the 

 soil around honey locusts, it failed to control mimosa 

 webworms on the trees. 



The basic problems in using a systemic insecti- 

 cide were found to be (a) development of methods of 

 application and dosages that will not injure plants but 

 will provide control of pests and (b) development of 

 safe methods for handling a highly poisonous chemical. 



LITERATURE CITED 



Jeppson. L. R., M. J. Jesser, and J. O. Complin 



1952. Tree trunk application as a possible method of using systemic insecticides on citrus. Jour. Econ. Ent. 

 45(4):669-71. 

 Norris, Dale M., Jr. 



1959. Potentialities for systemic control of the insect vectors of Dutch elm disease. N. Cent. Branch Ent. Soc. 

 Am. Proc. 14:59-60. 



Norris, Dale M., Jr. 



1960. Systemic insecticidal action in the cortical tissues of elm twigs. Jour. Econ. Ent. 53(6):1034-6. 



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