In order to make the right choice of chemical control contact the Information Service in your country. Every country has its own regulation for chemical control (insecticides and herbicides). We will only describe the diseases so that it is easier to recognize them.
CRIOCERIS DUODECIMPUNCTATA (RED) / CRIOCERIS ASPARAGI (BLUE)
These blue and red beetles lay their eggs on the fern. The larvae chew on the fern causing the stem to turn brown and reducing the yield the next year. Damage can be done especially to first and second year crops. The disease usually begins by affecting a few plants here and there but it can spread quickly.
This dark fly with light spots on its wings can be easily recognized on a field of asparagus. The flies are active from the end of April to the beginning of July. Only one generation appears per year. They lay their eggs in the tips of the young stems. The larvae eat holes into the stems just underneath ground level and pupate in the stems. The affected stem grows crooked and dies off prematurely. The aphid is most active in hot weather.
Apart from using an insecticide removing the leafage in winter will reduce the risk of infection.
Bean seed fly
Delia Platura lay their eggs inside the stems during the harvest season. The larvae eat holes into the stems, thereby making them unsuitable for consumption. Some years the crop is affected by this insect, some years it is not.
This fungal disease causes leafage to die prematurely so that the plant cannot store enough nutrients for the next season. This fungus occurs in both new and old fields. Chemical control should take place from the moment the flowers fall off the leafage, because botrytis can enter the plants through the tiny wounds.
A dense crop will demand more attention than an open crop. High temperatures, high humidity and periods in which the leaves are wet for more than six hours in a row can lead to infection.
This fungal disease starts in spring as rusty oblong orange patches on the base of the stems. In the summer these reddish-brown pustules spread all over the leafage. In autumn the foliage turns brown and drops. The affected stems and stem parts die.
This disease can be recognized by the occurrence of oval spots on the stems and leafage which makes them die prematurely.
Fusarium Root Rot
FUSARIUM OXYSPORUM ASPARAGI
Fusarium root rot is a soil-borne fungus that causes plants to wilt, turn brown and become stunted. Brown oval rotting spots can be found on fleshy roots. Infected roots have a reddish-brown colour instead of the white colour of healthy roots. The hair-roots die.
Disturbing ground layers and water in the root zone are often the cause of this disease. Especially if this situation leads to damage to the roots. The best way to avoid the disease is to start with healthy plant material
The plants can be dipped in a fungicide before they are planted. If they have been dipped it is important that the plants should not dry up before they are planted.