TY - JOUR AU - Wolcott, George N. PY - 1954/04/01 Y2 - 2024/03/29 TI - RESIDUAL EFFECTIVENESS OF INSECTICIDES AGAINST SOIL-INHABITING INSECTS JF - The Journal of Agriculture of the University of Puerto Rico JA - JAUPR VL - 38 IS - 2 SE - Articles DO - 10.46429/jaupr.v38i2.12712 UR - https://revistas.upr.edu/index.php/jaupr/article/view/12712 SP - 108-114 AB - Results of tests with just-hatched grubs of <em>Diaprepes abbreviatus</em> L. as biological indicators of the residual effect of insecticides mixed with soil were much more consistent and showed little loss of toxicity in 3 years as compared with the tests using field-collected white grubs. Thus tests with third- or last-instar grubs of <em>Phyllophaga</em> (or <em>Lachnosterna</em>) <em>portoricensis</em> Smyth and <em>P. vandinei</em> Smyth, as well as with first-instar white grubs of these species, although not entirely conclusive, appear to indicate that, after being mixed with soil for 3 years, Chlordan is not nearly so toxic to white grubs as when originally applied. But the latest results with weevil grubs are almost identical with those of 3 years ago. Even when freshly applied at the rate of 10 pounds per acre, the gamma isomer of benzene hexachloride did not kill just-hatched grubs of <em>Diaprepes abbreviatus</em> L., and cannot be recommended for field application to soils infested with them. This insecticide continued to be almost as effective against white grubs 3 years later as when originally applied to soil infested principally with them. Aldrin appeared to be fully as effective against the weevil grubs of <em>Diaprepes abbreviatus</em> L., as when first applied 3 years earlier, and was found to be very toxic to the grubs of <em>Ligyrus</em> (which are of very minor economic importance). Even if it is less toxic to third-instar <em>Lachnosterna</em> white grubs at the concentrations recommended for original field application (2 pounds per acre) it will kill these grubs in the first-instar. DDT appeared to be only slightly toxic to <em>Ligyrus</em> grubs as compared with Aldrin. For cucumbers and for the grubs of <em>Diaprepes abbreviatus</em> L., and the endemic species of <em>Lachnosterna</em>, DDT experienced no appreciable loss in toxicity in the soil with which it had been mixed 3 years earlier. ER -