Predicting Conditions to Aid Crop Control

By Beardall, Mike

Growers can benefit from new technology that warns of potential pest and disease threats. Mike Beardall reports Weather stations and micro-climate monitoring have become major weapons in the battle against pests and diseases in crops.

With the development of equipment linked to computers, accurate print-outs give growers precise models on which to base spraying programmes against pests and diseases in specific crops.

Growers can now create condition models for individual crops and locations that will indicate when they are at risk and the optimum times to spray.

Lancashire-based vegetable consultant Fred Tyler says: “Systems have never been more accurate in recording temperatures, leaf wetness and humidity the three key components in forecasting the onset of disease.

“In brassicas, particularly, we can measure conditions and put them against the model situation for diseases like ringspot, dark leaf spot, white blister and light leaf spot.

“By spraying only when it is appropriate and at the most efficient time, growers can save a great deal of money through not wasting products – and disease prevention is at its most effective.”

Tyler has been working with models developed by Warwick HRI through the Morph system and using Smaartlog weather-monitoring stations and software, developed byAardware Design of Walton-on- Thames, Surrey.

Smaartlog offers a system that can be adapted and expanded to fit an individual grower’s specific requirements, from a single-sensor standalone system to a 1 7-sensor system with remote communications. Weather data is downloaded and analysed in the software and can be exported to bespoke horticultural software.

One of the system’s designers, Graham Moss, says: “Growers have to have as much easy-to-use data as possible and be able to put it against disease and pest models. We have made this as up-to-the- minute as possible and results from growers across the country have shown it to be hitting the target.”

From 1 July, brassica growers in Lincolnshire will receive alerts direct to their mobile phones of high disease-risk conditions, as part of a free service run by Syngenta. The Brassica Disease Warning System uses spore-trapping and disease-monitoring information from the Lincolnshire-based Allium & Brassica Centre, combined with in- field weather data and a predictive model developed by Warwick HRI.

It provides a risk assessment for Alternaria, white blister and ringspot, based on field traps across Lincolnshire, the North East and South East. The forecasts are the result of extensive research and development undertaken by Warwick HRI, with funding from both Defra and the HDC. Information comes from seven monitoring sites across Eincolnshire.

Allium & Brassica Centre joint managing director Andy Richardson says: “Advance warning of disease enables better timing of protective fungicides and the opportunity to produce the highest- quality brassicas.”

In onions, susceptible to downy mildew, growers use similar condition models to those in potato blight prediction, he adds. Potato growers use the Blightwatch network, through ADAS and the Met Office, which monitors atmospheric conditions in 650 post-coded areas of the UK and texts warnings to growers’ mobile phones (see panel, p34).

“Growers can be far more in control now,” says Mark Bullen, specialist crops commercial manager at Syngenta, which has developed monitoring systems for growers that not only predict disease and pest attack but recommend the correct products to apply. He adds: “Knowledge is vital and puts the grower in a stronger position to make correct decisions about when to spray.

“General weather data from the Met Office is useful, but information from specific fields and knowing about localised weather patterns, wind, airflow and the like means you can spray at the right time.”

Bullen believes that in the past five years or so, monitoring equipment has become far more efficient, and growers now have much greater control over when to treat crops.

Agri-tech Services managing director Simon Turner agrees. “Growers should be in the driving seat with their own equipment,” he says. “The grower puts statistics into the computer and this information is put against the model for the specific crop.

“The results today are really accurate and microclimates can be monitored in small areas, rather than referring to statistics from some miles away.”

He adds: “There is a danger of relying on technology too much. Most growers are experienced enough to know their crops and local conditions. They will still use their own knowledge and observation but monitoring equipment and computer predictions are terrific management tools.”

Turner’s company has more than 200 clients using weather stations, mainly the Davis Vantage Pro.

Nottinghamshire-based Fresh Growers chief executive Martin Evans, who is also chairman of the British Carrot Growers’ Association, has used Dacon weather stations linked to computers for some years to help determine optimum times to spray against diseases and pests.

But he is not entirely convinced that new technology holds all the answers, believing that it is the skill and experience of growers – plus “getting out on the ground” – that determines final decisions on spraying.

“A 10ha field can have rainfall variations of as much as 80 per cent.” says Evans. “So a rainfall monitor in one corner will only give you the reading for that area. Weather stations are fine but it is a combination of the old skills and the new information that is used in the decision-making process.

“You cannot rely on computers entirely to tell you when to spray. There is a lot of precision equipment around but there is a risk if you put your faith in it 100 per cent. Experience tells you when the risk is greatest and I think we can be hoodwinked into assuming there is a perfect pest-and-disease model for every situation.”

The 12-member Fresh Growers group has 8,000ha across Nottinghamshire and North Lincolnshire and grows eight per cent of Britain’s carrots – along with 90 per cent of the country’s Chantenay carrots – plus asparagus, sprouts, cabbages and lettuce.

“We plan to have zero tolerance in chemical residue, and that means careful use of spraying,” says Evans. “Forecasting and predicting is vital, but we have to be realistic and use local knowledge as well as scientific information.”

Dr Richard Harrington of Hertfordshire-based Rothamsted Research says monitoring and forecasting systems are becoming crucial for growers as climate warming continues.

“The general implication is that, with climate warming, insect pests are set to be a greater problem for UK growers. Incrop inspections and pest-monitoring systems will have to be ready to cope with the threat, but can provide growers with the crucial information to take action early and effectively.”

Climate change will have a dramatic effect on vegetable and potato pest populations in the future, he adds. Mealy cabbage aphid can be expected to be much more of a problem, while the risk of cabbage root fly may increase, with each generation appearing earlier and three generations occurring in the few remaining areas and years that currently have two. Diamondback moth may also increase problems if it is able to overwinter in milder conditions, but the damage caused by turnip moth could be reduced if heavy spring rain becomes more normal, as this will kill larvae.

Harrington also warns potato growers that it may be increasingly difficult to keep out Colorado beetle if conditions continue to warm up.

“We anticipate first disease alerts for Altemaria and ringspot being triggered around the end of June or early July, but with many growers not starting fungicide programmes until August, disease can build within the crop,” warns Richardson. “Starting spray programmes earlier and timing sprays in conjunction with a disease-forecasting system is the key to control of foliar diseases, particularly with fungicides such as Amistar.”

Syngenta specialist crop manager Bruce McKenzie adds: “The more help that growers can get from modern forecasting methods, the better they will be able to treat crops before problems start. Pest and disease warnings give growers extra support in making informed decisions.”

Crop protection: monitoring systems can help growers calculate the optimum time to spray crops, leading to minimal damage and the chance to produce the highest-quality harvest

NEW PRODUCT

US-based Spectrum Technologies recently launched “affordable solutions for growers” at Plumpton Agricultural College in East Sussex.

The Watchdog 2000 atmospheric recording unit, which retails at around Pounds 1,000, uses wireless communication systems from field sensors to a computer to predict disease onset. Alerters, which can be linked to mobile phones, suggest optimum times to apply fungicides and pesticides.

“The system monitors more than a dozen important growing conditions for effective crop and pest management,” says Spectrum’s international sales director David Lau. “The LCD display reviews historical data and can show severity indicators from onboard plant- disease models. This equipment gives growers a complete picture of environment conditions.”

Distributed by Weather Front of Eastbourne – which also markets Davis weather stations under its EnviroMonitors banner-Watchdog 2000 includes a digital microscope that sends a picture of leaf and stem surfaces to a computer to be emailed for analysis. The system starts at around Pounds 250, including the software.

“Knowledge is vital and puts the grower in a stronger position to make correct decisions about when to spray”

Mark Bullen, specialist crops commercial manager, Syngenta

BLIGHTWATCH

Blightwatch, run by ADAS and the Met Office, offers potato growers a unique warning system of impending blight threat conditions.

Growers in 650 monitored areas get a text alert to their mobile phones warning of the need to spray. While most potato growers monitor their own localised conditions with weather stations, the Blightwatch system has proved a valuable extra precaution.

Danger times are “Smith periods” when at least two consecutive days have a minimum temperature of 10[degrees]C and on each day at least 11 hours have relative humidity greater than 90 per cent. Smith period conditions are conducive for sporulation of the potato blight pathogen on lesions – and leaf wetness is also necessary for infection to occur. If these periods occur at seven- to 10-day intervals, there is a greater chance of blight development.

Smith periods are only an aid to decision support and do not in themselves always indicate the need for immediate application of a fungicide.

The Met Office collects hourly weather information from a network of more than 100 stations in the UK. Traditionally. Smith periods for potato blight warnings have been calculated from these station values.

“Smith Periods are only one management tool and do not predict weather conditions on a field-by-field basis,” says an ADAS representative. “At this level, the slope, aspect and effects of the local microclimate have an influence. This must be borne in mind when deciding on spray programmes.”

Spraying potatoes: Blightwatch system tells growers when to spray against blight

Copyright Haymarket Business Publications Ltd. Jun 19, 2008

(c) 2008 Horticulture Week. Provided by ProQuest Information and Learning. All rights Reserved.