Survey and Assessment of the Natural Enemies of Water Hyacinth,Eichhornia crassipes

Abstract

In northern Queensland, the addition of 2,4,5‐T butyl ester was found to be unnecessary to maintain the control of Echinochloa colona (L.) Link and Cyperus Iria L. In dry seeded rice when propanil rates were reduced below the registered rate of 4 kg a.i. ha^?1. Adequate weed control was obtained with 1.3 kg a.i. ha^?1 propanil alone. No adverse effects on rice yield were found with any of the propanil × 2,4,5‐T treatments. Low rates of propanil, 1.3 and 0.72 kg a.i. ha^?1, compared favourably with pre‐emergence treatments of thiobencarb, butachlor, oxyfluorfen and pretilachlor (plus a safener) when weed yields were low. Where water management was poor and Ischaemum rugosum Salisb. was the dominant weed, oxyfluorfen applied pre‐emergence at 0.96 kg a.i. ha^?1 produced a higher rice and a lower weed yield than the low rates of propanil. In three of the five experiments, weed growth was insufficient to depress rice yields significantly.