Dr Becky Howard discusses the best ways of dealing with pests in bean crops via the PGRO’s online roadshow. Wendy Short reports.

THE Processors and Growers Research Organisation (PGRO), which represents pulse growers, took its annual roadshow online for 2021. Dr Becky Howard focused on tackling pests in the face of the ever-dwindling range of chemical treatments available to farmers.

Integrated pest management (IPM) has become an increasing element of pest control for pulse crops and the PGRO has for some years been working alongside makers of monitoring and forecasting systems. It is vital that growers identify the number of crop pests present, before any preventative action is taken, said Dr Howard.

Webinar viewers were told about the launch of a new project in January 2021. It will test the efficacy of trap-cropping systems for the management of bruchid beetle and pea and bean weevil within field bean crops.

“We are collaborating with farmers to establish sites where legume-based trap crops can be grown,” explained Dr Howard in the January webinar. “These are planted as marginal blocks or strips within the primary crop, with the aim of reducing the level of damage.

“Among the species that will be sown are vetches and lucerne. These have been chosen because they are also host plants for bruchid beetles and weevils. Our project, which has been co-funded by the Swedish Ekhaga Foundation, will take these ideas to another stage as the trap crops will be used in combination with pheromone lures.”

Trial data has already shown that an area of early-sown field beans, grown as a trap crop next to the primary crop, also has the potential to act as an alternative pest control method, she said. It has been established that when beans are sown at varying times, the earlier-sown crop will be subject to a higher level of damage, compared with later-sown plants.

“Vetches are also reported to be a host for the bruchid beetle. The PGRO will test whether they can be used to attract bruchids, leaving the main crop less vulnerable to attack. Trap-cropping will also be tested in conjunction with insect pheromone traps in this trial.”

A pea and bean weevil monitoring system will be available again commercially from this month, added Dr Howard.

“The pea and bean weevil has become particularly problematic in early-sown crops, due to the development of resistance to pyrethroid insecticides. There is no other chemical treatment available, so monitoring has become even more important. Nevertheless, the recommended threshold number for the traps is fairly high and therefore many growers may not necessarily need to take any action.”

Meanwhile, the bean seed fly has a wide range of hosts, including peas and beans. The larvae have the potential to cause serious crop damage by eating the seed, as well as the emerging seedlings.

“There is no longer any chemical control on the market for either the bean seed fly larvae or the adults,” she said. “Pest numbers have risen significantly over the past few years and some vining pea growers have suffered high losses at the crop establishment stage.

“Early trial data suggests that the period between cultivation and drilling is critical. It is believed to have a greater effect on damage from bean seed fly than the choice of drill, or whether the pulse seedbed has been rolled.

“The maximum level of damage occurred within the plots that were drilled on the same day as cultivation, with the lowest levels recorded on areas that were cultivated 21 and 28 days ahead of drilling.

“A survey of trial fields at 20 sites in Yorkshire and Lincolnshire underlined this theory, by confirming that cultivating the land a few weeks before drilling, rather than on the day of drilling, reduced bean seed fly damage by as much as 20 per cent.

"It is thought that the flies are greatly attracted to newly-cultivated soils, particularly when they contain large quantities of weed or crop debris, or farmyard manure.”

Dr Howard reminded growers that bean seed fly presence can be reported in any crop using the PGRO app. The tool monitors pest activity in various crops across the country and pinpoints areas that may be at high risk. It can be downloaded from Apple and Google stores.

She added that significantly fewer chemical treatment products are being brought to market.

“We are aiming to build management systems that make full use of cultural techniques to give enhanced control of pests” she said. “It is unrealistic to expect that cultural methods will completely solve the problem of insect damage in pulses, but they will reduce or remove the need to apply insecticides and should be fully utilised before chemical treatment is implemented.”

Monitoring systems: Pea and bean weevil; pea moth; silver Y moth; bean seed fly – monitoring systems are available from Koppert UK. Pea moth and bean seed fly – monitoring systems are available from Andermatt Biocontrol UK. Pea moth – monitoring systems are available from Dragonfli Ltd.