PGRO Crop Update 1 - 4th March 2015

Sowing rate of spring beans and peas

The optimum plant density for spring beans is 45-55 plants per sq. m established. Use the following to calculate seed rate (Allow for a 5 - 10% seed bed loss).


Seed rate kg/ha =
thousand seed weight x target
populations plants/m²


x

100
  % germination   100 – (field loss)

The calculation is also used for peas and optimum plant populations are as follows:
Marrowfats – 65-70 plants per square m
Large blues and whites – 70 plants per square m
Small blues – 70 plants per square m
Zero 4 (small blue) – 110 plants per square m

Don’t rush planting – it’s better to wait for good soil conditions rather than try to stick to calendar dates.

If possible, choose varieties with good downy mildew resistance or apply a seed treatment for control of primary downy mildew. This will also give control of seed-borne diseases such as Ascochyta pisi and Mycosphaerella pinodes. Downy mildew is a soil-borne disease that can affect yield and quality. Details of the relative resistance to downy mildew can be found in the PGRO Pulse Agronomy Guide, which includes the PGRO Recommended List of peas. This is available on our website at www.pgro.org

Pre-emergence herbicides

Cost effective pre-emergence herbicide options are dependent on moisture availability. Additional factors such as cloddy seed beds can influence whether adequate weed control is achieved. Rolling helps conserve moisture and break up clods, and application with appropriate angled nozzles may help if the surface is cloddy.

Several pre-emergence products and tank mixes are available for combining peas and spring beans. In addition to Nirvana, Centium, various pendimethalin products (approved for peas, EAMU beans) and Defy (EAMU beans only), Afalon (linuron) and Linzone/Lingo (linuron + clomazone) are also approved for use in combining peas and spring beans. Dual Gold (S-metolachlor) has an EAMU in beans. Stallion Syn tec (pendimethalin + clomazone) has approval in both spring peas and beans.

Pea and bean weevil

Pea and bean weevils are likely to become active at the weekend as temperature increases. Spring peas and beans that will emerge in the next two to three weeks will be at most risk of damage as they emerge. Although foliar damage doesn’t generally cause a problem, crop growth may be delayed 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 in spring peas or beans, 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. Winter beans may suffer less damage as they are generally well established by the time weevils are active.

Field thrips

Field thrips may be present in peas and beans, and 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 most 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 rust colour on the under-surface of leaves. Thrips can be found within the developing growing point and 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.