Compensation is the ability of the plant or crop to offset damage caused by pests or other factors such as hail. Compensation can act at the plant or crop levels. Plant compensation refers to the ability of individual plants to regrow after damage. Crop compensation may arise when damage is not uniform, i.e. crops compensate when insect attack on one individual allows its undamaged neighbour to grow faster. In this paper we present results of an experiment that shows that a plant next to a damaged plant yields more than it would otherwise.

Two years ago, the computer program entomoLOGIC 1 was first made widely available to cotton growers and consultants. It was designed to assist in management of insect pests on cotton through the use of models of crop and pest development and other technology including a valuable record keeping capability. These functions serve a common purpose; better decisions can be made with the experience and understanding gained by good records of what has occurred in the past, and good reporting of what is currently happening on the farm. The models and other new technology can then assist in analysing the immediate crop and pest situation

Pix is now in common use to manage vegetative growth of cotton in Australia. I presented a paper at the 1992 ACGRA Conference detailing how to evaluate potential responses to Pix. That procedure utilises regular measurements of plant height and node numbers. Plant growth is assessed on recent development, rather than using average node lengths. Since it is usually too late to obtain yield responses to Pix once a crop is already too tall, this procedure allows problem situations to be diagnosed before excessive vegetative growth occurs. The results of that study are summarised in Figure 1. They show that internode increases of less than 5.5 cm lead to no response or even negative yield responses to Pix.

A great proportion of the Helicoverpa eggs laid onto cotton never hatch. They are either eaten by predators, dislodged from the plant by wind and rain, killed by climatic extremes, or are infertile. If we could accurately predict the level of natural mortality of eggs, growers would be better placed to make control decisions. Utilising the natural mortality of these pests would allow growers the option of sometimes reducing or avoiding insecticidal controls when natural mortality rates are high. A reduction in pesticide application holds many benefits, especially early in the season, when sprays can disrupt the establishment of beneficial insects which are important for the integrated control of both Helicoverpa and mites in cotton. Over the past three seasons, research has been carried out to determine the levels of natural mortality in Helicoverpa eggs, the primary factors causing this mortality and changes in rates of mortality throughout the season. In addition to this, preliminary studies on the establishment and behaviour of newly hatched Helicoverpa larvae on cotton have also been conducted

The residual action of nine insecticides commonly used in cotton were assessed on the survival of the native egg parasitoid Trichogramma funiculatum by exposing adult wasps to sprayed cotton leaves 1, 3, 5, 7, 1 O and 14 days after treatment (DAT). Es-fenvelerate (.025% a.i.), betacyfluthrin (.02% a.i), methomyl (.045% a.i.) and thiodicarb (.075% a.i.) were highly toxic to the wasps, while endosulfan (.07% a.i) and profenofos (.075% a.i.) were not significantly toxic from DAT 3 onwards. Bacillus thuringiensis (30 ml/L), chlorfluazuron (.02% a.i.) and omethoate (.02% a.i.) had no significant adverse affects on wasp survival

Having previously identified poor N recovery as largely a denitrification problem, research began to investigate means of reducing N loss. In theory, denitrification Joss can be reduced by controlling the concentration of nitrate in the soil using nitrification inhibitors (which retard the oxidation of ammonium to nitrate), thus reducing the amount of nitrate available to the denitrification organisms. A recently-completed 3-year project evaluated the ability of nitrification inhibitors to improve N fertilizer recovery.

Various parasitoids of heliothis have been considered in integrated pest management programs throughout the world. Despite the rhetoric that parasitoids have an important role in heliothis management, their niche in Australian cotton fields has yet to be fully evaluated. In this paper we present information from Darling Downs trials where egg and larval parasitoids were released as components of an integrated approach tO pest management.

The aim of the project outlined here is to try and develop the SOLICON techniques that are already being used by soil researchers in order to find a practical technique available to cotton consultants or agronomists (SOLICON 2) that gives an accurate analysis of soil compaction. Here a new, cheaper field technique for acquiring images of soil structure using paint is compared to the existing resin method. The existing method of impregnation (6 & 7) is labour intensive; it talces at least two days of field work followed by at least 2 hrs per sample of laboratory work (reimpregnation, grinding and photography) before the images can be analysed

Management of insect and mite pests attacking cotton crops relies heavily on the use of insecticides. In raingrown crops on the Darling Downs, an average of 8 to 12 insecticide sprays are applied to control the major pests - thrips, mirids and heliothis. In order to reduce the dependence on insecticides in cotton production, alternative management tactics are being evaluated as part of a program towards the development of an integrated pest management package. One of the key elements of our approach was to evaluate parasitoids.

Larvae of one Helicoverpa punctigera and three Helicoverpa annigera strains were stressed by feeding early 3rd instars on artificial diet containing 0.015 mg DiPel 2X (32,000 IU/mg) per ml of diet. The percentage of larvae reaching testing size (that is early 4th instars weighing 30-40 mg) by 10 days from the early 3rd instar (weighing< 5 mg) was 65-75% & 90% for H. armigera & H. punctigera respectively, compared to 99% for the control diet. In addition, those larvae that did survive were about twice as slow to develop from the early 3rd instar to testing size (2.9 & 5.7 days for control and Bt diet, respectively). When larvae reached testing size, they were placed on fresh untreated diet and bioassayed with either fenvalerate, endosulfan or profenofos representing the three major classes of conventional insecticides used against Helicoverpa spp. in Australia