PGRO Crop Update (20.03.14)

Sowing rate of spring beans and peas
The optimum plant density for spring beans is 40 plants per sq m established.  Use the following to calculate seed rate (allow for a 5 - 10% seedbed loss).

Required population x 1000 seed weight     x             100
% germination                                     100 – seedbed loss

The calculation is also used for peas, and optimum plant populations are as follows:

Marrowfats: 65 plants per square m / Large blues and whites: 70 plants per square m / Small blues: 70 plants per square m /  Zero4 (small blue): 110 plants per square m

It is important to ensure that soil conditions are right for drilling. Peas and beans should not be forced in under difficult conditions.

Pre-emergence herbicides
Some crops of spring beans are not rolled following drilling and may not need it. Rolling helps conserve moisture and break up clods, giving a level surface to ensure that best ground coverage is achieved with residual herbicides.

If the surface is cloddy, then application of pre-emergence herbicides with appropriate angled nozzles may help. Following recent waterlogging in some areas, it is worth considering whether rolling will adversely affect below ground soil conditions.

Several pre-emergence products and tank mix options are available for combining peas, spring beans and vining peas.

In addition to Nirvana (imazamox + pendimethalin), Centium (clomazone) and Linzone/Lingo (linuron + clomazone) which have full approval in all three crops, there are pendimethalin formulations approved for combining peas but only available on EAMUs in spring beans and vining peas, Dual Gold (S-metolachlor) has an EAMU for use in spring beans and vining peas, Defy (prosulfocarb) use is via an EAMU in spring beans and Afalon (linuron) has approval in combining peas and spring beans.

Pea and bean weevil
Pea and bean weevil is very active due to mild weather. Recently-sown spring beans, and those sown in the next few weeks, may be at risk of damage as they emerge. Although foliar damage doesn't generally cause a problem, crops can be held back if damage is severe at very early emergence.

Spraying will prevent egg laying and larval damage to root nodules. If you have a history of severe damage, particularly in drier areas, a pyrethroid spray should be applied at first signs of leaf-notching, and a second spray ten to fourteen days later where damage is persistent.

Be aware that there is a limited range of products available for use later in the season for bruchid control. It is advisable to use different products for weevil control. Winter beans may suffer less damage as they are generally well established by the time weevils are active.

Peas are susceptible and should be sprayed when first notching is seen, followed by a second spray ten to fourteen days later.

Field thrips
Field thrips may also cause problems in peas and beans, although damage is generally more severe in dry, cold springs.

Early-sown spring peas and beans, growing on calcareous soils with a high proportion of stones, are susceptible to damage. Shoots of newly emerged seedlings are pale and distorted and growth can be retarded. Leaflets may be puckered and leathery with small translucent spots on the leaf surface.

Beans may develop a rusty-coloured under-surface. Thrips can be found within the developing growing point. If cold weather persists, peas can remain stunted and not recover. Prompt treatment of newly emerging seedlings is essential where there is a history of severe thrips damage.