Fruit crop protection: Filling the gaps

 
The past couple of years have been bad for fruit growers in terms of crop protection product withdrawals. Big losses for the industry included stalwarts for bush and cane fruit, with tree fruit also taking a hit.

Casoron, for example, may have made short work of perennial and annual weeds on strawberries and blackberries, but the granuals were no match for safety chiefs. It was blitzed around springtime from the ever-dwindling armoury of crop-protection products for growers. Ramrod, a trusty friend of strawberry growers struggling with annual weeds, was also banished.

Turn back the clock a bit further, and you will find a crucial herbicide for fruit crops taking its final bow. Simazine, insists ADAS herbicide specialist John Atwood, was one of the main products used for fruit crops and the basis of most weed-control programmes. He is no less insistent that the continual loss of chemicals is leaving frightening, ever-widening gaps in fruit protection.

"There is nothing to replace Casoron and its loss has made control of perennial weeds very tough," he explains. "They used to be well contained with only one application in spring, but now the only control is the use of glyphosate from a hooded spray into the bush, which is hard during the growing season."

Bayer horticultural account manager Peter Newman agrees that fruit, especially top fruit, has had a tough year, with supermarkets increasingly demanding spotless produce. But then growers have been known to skimp - two thirds of production costs for Cox and Gala apples coming out of cold store this year were spent after harvest.

"Costings suggest only one third of the total production cost per kilo went into fruit before picking," he explains. "On average, 12 per cent of costs go on growing and only four per cent of costs go on crop protection. There is too much attention on making savings with crop protection against costly labour, grading and storage. But protection has a direct bearing on the quality of the fruit.

 "Anything less than class 1 fruit loses money for growers, who won't cover costs for picking, storing and grading imperfect, blemished fruit. Yet crop protection is a relatively low cost and it's a false economy to trim, leaving you with a quality control chink in the programme through using cheaper alternatives or stretching spray intervals."

He says a "sound, robust" crop-protection programme is a minor investment against the positive impact on financial performance. Bayer, he adds, is screening and bringing new products to the fruit market and this "exciting pipeline" will include three or four fungicides and insecticides over the next few years. But there is no magic solution.

"There is definitely no silver bullet out there - the nearest we've had were the old broad-spectrum chemicals like DDT, which were so wide in their reach, scope and persistence. As safety and environmental registration becomes more demanding, new products tend to be less broad-spectrum. Without silver bullets we will need accurate but more specific products."

This puts a double bind on growers, he points out. As the older, broader-spectrum chemicals vanish, the industry is seeing the return of pests such as apple sawfly, weevils such as Rhynchites and flat scarlet mite. Fortunately, chemicals such as Bayer's Calypso and Envidor have a big enough spectrum of actives to fight pests such as mussel scale.

"Historically, pests such as mites have developed resistance to widely-used insecticides. Red spider mite, for example, developed resistance on young fruit trees in nurseries in Holland and Belgium - a main source of trees for England. This change in problem pests and tightening of rules on actives means new chemistry is very important."

Meanwhile, flat scarlet mite has another for in the shape of Syngenta's insecticide Agrimec, for which the Horticultural Development Company has gained a specific off-label approval (see p30).

Spider mites also have another foe. The insecticide Majestik won on-label approval last month for use on all edible crops, including soft and top fruit. Certis technical officer Alan Horgan says the approval allows growers to use the product in the field as well as on protected crops, while the impact on beneficial species is "short lived".

"The label permits use on all crops, indoor and outdoor, making Majestik a flexible product," he explains. "This is a particular benefit for minor crop categories. Majestik can also be used with a zero harvest interval, a feature of its short persistence, and has no restrictions regarding operator safety. It's also permitted for use in organic growing systems."

According to Horgan, Majestik achieves 98 per cent control. His Certis colleague Morley Benson says such high performance is a must, given the tough market and the need to adapt crop protection to meet retailer and consumer trends while still producing class 1 fruit.

"The definition of 'conventional' production methods, and what is classed as a 'plant protection product', is changing," he says. "Retailers are becoming more stringent, placing increasing importance on environmental practices, encouraging use of biological controls with strong emphasis on alleviating and preventing resistance issues.

"But at the same time the list of approved pesticides becomes ever more limited. For top fruit we focus more on the cropping stage, with conventional treatments favoured from post harvest. This allows targeting of overwintering pest stages with minimal impact on beneficial insects. From post-blossom to harvest, organic and integrated pest management solutions are favoured."

Embracing such an approach and preserving beneficial predators enables growers to tackle codling moth, arguably the most important issue in top fruit worldwide. Certis product Cyd-X is the UK's first "granulovirus" pesticide and "can be used standalone in organic systems, or alongside traditional pesticide treatments," says Benson.

"Timing is everything - monitoring through the use of pheromone or sticky traps is vital, supplementing control and indicating pest presence. Monitoring has also moved on and computer modelling systems specific to codling, scab, light-brown apple moth and rosy apple aphids are helping give the best chance at effective control."

All is not lost, thanks to reinforcements from products, newly minted with specific off-label approvals (SOLAs). ADAS herbicide specialist John Atwood says more good news stories are likely in the coming months as he and colleagues work on new products.

Recent launches include Artist for the full range of bush fruits. BASF fungicide Scala can also be applied to some fruit crops, including blackberries, thanks to a SOLA released earlier this year - while soft fruit has an extra guardian in the form of Syngenta fungicide Fubol Gold after a SOLA issued last year.

"The situation isn't completely bleak," says Atwood. "The Horticultural Development Company (HDC) has done a good job on getting SOLAs and there are still some residual herbicides. But it will get harder because there aren't as many active ingredients being developed, and another issue is meeting the Water Framework Directive.

"We are looking at utilising herbicides from other sectors such as vegetables and maize. But we will probably have to use more applications because these products don't last as long. Fortunately, there has been more cooperation with other European countries in exchanging data for SOLAs."

Sceptre, a project for looking into products including bio-herbicides, is a joint HDC/ADAS initiative involving growers and chemical companies. Atwood says it is early days in terms of major breakthroughs. But will bio-treamtents ever compete with chemicals? "We will wait and see," he hedges.

Growers have other weapons in their armoury to improve targeting of chemicals, says Agrovista agronomist Paul Bennett. More soft and top fruit growers are using so-called forecasting models to help combat pests and avoid wasting chemicals. The web-based prediction model, Agrovista Growers Choice Interactive, forecasts codling moth mating and egg hatching.

"There's growing pressure from many of the major retailers for reduced residue or even residue-free fruit," he says, adding that such systems enable growers to hone the timing of their insect treatments to trim costs. "With residue-detection measures improving, there is a real drive towards the use of alternative non-chemical options."

So a flexible and open-minded approach to crop protection is important, says Angela Berrie, a research leader in plant pathology at East Malling Research. "An integrated pest management programme is essential. You need to monitor crops to identify what to spray and for how long, and you need to look at application of products near to harvest to ensure you meet the requirements of your customers.

"The days of spraying on certain calendar days are gone and the younger generation of growers have to be - and are - very knowledgeable. Fruit growing has become so professional because it is all about producing high-quality produce with minimal residues. If you don't have a professional approach to crop protection these days, you won't achieve the end product."