Supporting IPM for future cotton systems

Date Issued:2008-06-30

Abstract

1) The fit of new insecticides into integrated pest management. Selection of insecticides can have a

big influence on both control of the target pest as well as on beneficials, and the risk of secondary

pest outbreaks. We found that low rates of fipronil provided strong efficacy against mirids, with

or without salt, and were significantly more selective that the full rates of fipronil against

beneficials, though still with a risk of flaring mites. Low rates of indoxacarb alone provided poor

efficacy against mirids but the addition of salt or canopy oil boosted this to efficacy equivalent of

the full rate with low risk to beneficials or risk of flaring mites. Altacor (rynaxypyr) a new

insecticide for Helicoverpa control was highly efficacious and selective against many beneficials

indicating a good IPM fit. These results have been made available to industry via the Cotton Pest

Management Guide, to assist pest manager in spray choices, and to industry to help in

registration, thereby ensuring availability of new insecticides or uses of insecticides to industry.

2) Defining the pest status of emerging pests

a) Management of thrips on seedling cotton. Tobacco thrips, Thrips tabaci, is still the dominant

species. It was controlled moderately well at some sites but poorly at others, which could

indicate resistance. At some locations the western flower thrips, Frankliniella occidentalis, is

also abundant and poorly controlled by available options indicating insecticide resistance.

Control of thrips is problematic because damage is often cosmetic, plants will recover without

loss, and because thrips are also predators of spider mites. Nevertheless in cooler regions, where

control is justified, management of WFT may be difficult. Monitoring of thrips population

composition early in the season and determination of resistance profiles for both WFT and T.

tabaci has been initiated in conjunction with Dr Grant Herron (NSWDPI) and CSD.

b) Late season pest damage from thrips and jassids. These pests often build to levels causing

significant damage to leaves on maturing cotton. We found that late season damage to leaves is

only likely to reduce yield in crops with high yield potential and if the damage is very severe and

prolonged before cut-out. High yielding crops are likely more affected but even they show strong

compensation at yield levels up to 14 b/ha.

c) The effect of mirid sprays on secondary pests. We found that controlling mirids with the most

popular insecticide (fipronil) increases the risk of causing mite outbreaks, which would then

require additional control. Our results also suggest that in some situations Bollgard II crops are

more at risk – this deserves further investigation. Nevertheless, the results highlight the need to

have good mite sampling protocols in place in Bollgard II crops especially if OP’s, SP’s or

fipronil are used to control mirids.

3) Develop a new aphid sampling strategy and thresholds. These were developed and extended to

industry. They will provide a more rational basis for deciding when the occurrence of this pest

justifies control and when beneficials are providing adequate control. This information has been

linked with new information on the aphid borne disease cotton bunchy top, to provide pest

managers with a holistic approach to managing both the pest and the disease.

4) Sporadic pests. Information and publication to help manage the pale cotton stainer was completed

and will help industry to manage this pest in the future. In particular thresholds for lint damage

are now available. These indicate that for stained locks the threshold is >50% of bolls with all

locks damage, and for tight-locked bolls it’s > 20% of bolls with all locks damaged. We also

studied the feeding behaviour and have a better understanding of the damage symptoms.

This project has provided new information to help pest managers to make better decisions about

management of emerging pests. Outcomes have been largely delivered to industry through a range of

presentations, published resources and the WWW. Benefits to the industry are more rational decisions

on the need to control pests, and awareness of risks for different control options. This will contribute

to reduced pesticide use with flow-on economic, social and environmental benefits.

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