A telephone survey of lettuce growers was conducted in April and May of 2006.
The aim of the survey was to ascertain the pest management strategies of lettuce growers and to determine their level of uptake and understanding of Integrated Pest Management (IPM).
The survey form was very similar to the IPM survey form used by Andrew Creek in October 2005 .
Additional questions were added which included the use of fungicides and herbicides on lettuce crops, control of sclerotinia, the presence of currant-lettuce aphid (CLA) (Nasonovia ribisnigri (Mosley)) and local barriers that inhibit the uptake of IPM.
Other lettuce growers contacted from NSW and some from SA, Vic and WA were selected randomly from a list of growers compiled by NSW DPI throughout the lettuce IPM project.
Although this survey only reflects the opinions of a small cross section of growers from the Australian lettuce industry, it does however give an indication of the pest management strategies that lettuce growers are currently using.
The survey also reveals the attitude towards and the uptake of IPM.
|| Cathy Young
Of the 79 lettuce growers who choose to take part in the survey, 59 were field growers, 15 were hydroponic growers, 2 were organic growers and there was 1 seedling, transplant and non grower.
The non grower who participated had been a consultant for many years and was very knowledgeable with the pest management trends in their area.
This survey of Australian lettuce growers (predominately NSW and Victorian) has demonstrated that the growers are genuinely interested in alternative pest management strategies.
More than 60% of growers considered themselves to be IPM growers and used a range of techniques as part of their pest management strategies for lettuce.
Crop monitoring was the most popular technique followed by monitoring beneficial numbers and the use of biological insecticides.
The non IPM growers (39%) believed they were managing their pest situations traditionally by spraying weekly with older and newer generation chemistries.
Despite this, most non IPM growers are using some techniques that are considered to be IPM strategies such as crop monitoring, the use of yellow sticky traps, only spraying when necessary, chemical rotations and ploughing in crop residues.
Regular crop monitoring was a pest management strategy used by 91% of all growers surveyed. In total 74% of the growers monitored their own lettuce crops, whilst consultants and chemical resellers did 34% of the monitoring.
Monitoring protocols and frequency varied greatly amongst the growers. This depended on whether they were IPM or non IPM growers and if the lettuces were grown in the field, hydroponically or organically.
Those growers that did not monitor their crops relied on their experience, pest pressure at the time and moth activity at night to make their spray decisions.
Most growers thought that crop monitoring was cost effective in reducing the number of chemicals sprayed. The majority of growers have used newer generation insecticides, with Success® the most popular.
However, older chemistries such as Lannate®, Fastac® and Dimethoate® were still sprayed because at times growers felt that the conditions suited them better.
Dithane®, Filan®, Ridomil® and Rovral® were the fungicides of choice for growers to control downy mildew and sclerotinia. Kerb® was by far the most popular herbicide chosen by growers to manage both grass and broadleaf weeds.
Growers’ tank mixed both newer and older generation chemicals according to their compatibilities, which decreased costs somewhat. Conventional boom sprays were used by 49 of the 79 growers surveyed to apply chemicals to their lettuce crops.
Three IPM growers modified their conventional boom spray and added short droppers to improve spray coverage.
Air assist sprayers were the second most popular method of applying chemicals. Water application rates ranged from 30L/Ha up to 1000L/Ha, depending on the lettuce growers’ situation.
However, the most commonly used rates were 400L/Ha and 600L/ha. CLA was the major insect pest concern to come out of the surveys.
Most growers believed that CLA was the biggest pest threat to the ongoing success of lettuce IPM and were very happy with the available information on this pest. CLA has been found in Tasmania, the Sydney basin in NSW and the Werribee and Cranbourne (metropolitan) areas in Victoria. Just recently CLA was found in the Bathurst region of NSW and the Northern Adelaide Plains and Adelaide Hills regions of SA.
Nearly all of the growers thought that it was only a matter of time before CLA spread to most lettuce growing areas in Australia. Confidor® and Nas resistant lettuce varieties are the growers’ choice for controlling CLA.
Several benefits of adopting IPM were identified by growers.
The main benefit was related to insecticides and the reduction in use and cost. Better pest control, a greater understanding of insect pests and the ability to recognise beneficials were other important benefits.
Along with the benefits, weaknesses were also identified with the most common being a lack of confidence in IPM when the pest pressure is high. Growers indicated that with educational workshops the fear of failure may not be as great.
Coupled with CLA being a threat to lettuce IPM is the use of Confidor® to control the aphids. Growers are worried about the implications of spraying Confidor® and resistance problems. As well as CLA being an ongoing threat to the success of lettuce IPM, Rutherglen bug and thrips were other major pest concerns.
To enhance lettuce IPM the management of Rutherglen bug and thrips is considered to be important by the growers.
This is especially the case when consumers and retailers have a “zero tolerance” for any sort of insect contamination (including beneficials) on product. Many growers cannot afford to loose markets through contamination and are therefore worried about the lack of awareness of retailers and consumers.
Local barriers limiting the adoption of IPM were very similar to the threats. More specifically, Hay lettuce growers were worried that the biological insecticides lacked efficacy in their region due to hot and dry conditions. These insecticides need humidity to work successfully which is not a feature in the Hay region.
Around the Gatton region in Qld processors are not accepting IPM lettuces due to insect contamination and have banned the use of the insecticide Bt because of perceived health risks.
Other regionally based barriers included high insect pressures from neighbouring crops through to local council legislation. The growers who were surveyed had a very high opinion of the publications that have been a part of the lettuce project.
The Lettuce Leaf Newsletter, Ute/Field Guide and Lettuce IPM Information Guide were all rated good to excellent publications. The bimonthly Lettuce Leaf Newsletter was very popular because it was brief and supplied relevant and interesting information.
The Lettuce Conferences were also rated highly by those who attended. The conference proceedings were rated lower than other publications because the growers deemed them to be too technical.
Overall it would appear that the lettuce project has proven to be very useful for the growers. Most think that the lettuce industry is heading in the right direction and continued contact between growers, researchers and industry representatives is essential for a sustainable future.
The author would like to thank the growers who willingly participated in this survey, without their support it would have been difficult to complete.
This project was funded by NSW DPI, the AUSVEG levy, Horticulture Australia Limited and a voluntary contribution from South Pacific Seeds and Convenience Foods.
A list of potential survey candidates from Tasmania and Victoria was compiled by Lionel Hill (Researcher) and Patrick Ulloa (Industry Development Officer), respectively.
John Duff an Entomologist from Qld, Sonia Broughton also an Entomologist from WA and Greg Baker a Researcher from SA, surveyed growers from their particular states.