SCEPTREplus: Brassicas

EAMUs secured

Authorisations secured following SCEPTREplus trials for brassicas

• Serenade ASO as a fungicide on outdoor cabbage for the control of Botrytis cinerea as a post-harvest drench
• Teppeki as an insecticide on cabbage for the control of aphid and peach potato aphid

Grey Mould (Botrytis cinerea)

• Crop Group: Field vegetables – white cabbage
• Target: Grey mould
• Period: April 2017 – June 2018

Take-home message

Using post-harvest treatments significantly reduces the rate of disease and crop wastage.

Of the products tested, three currently have approval on cabbage heads, although in this study they were applied outside the current approvals.

AHDB9925 and AHDB 9924 gave good control and were comparable to Rovral WG, the withdrawn standard application.

An EAMU has now been secured for Serenade ASO for post-harvest application.

Trial summary

The loss of Rovral WG (iprodione) in June 2018 created a gap in the ability to control diseases in stored cabbage. This trial aimed to find new alternatives. We evaluated both conventional products and biopesticides for the control of grey mould.

Conclusions

Post-trimming weights

• AHDB9935, AHDB9926, AHDB9923 and Serenade all gave significantly increased yield compared with the water control

Marketable heads

• AHDB9925, AHDB9926, AHDB9923 and Serenade had significantly more marketable heads than the water control

Biologicals

• Of the three biological products tested, only Serenade appeared to give any control

Downy mildew

• Crop Group: Field vegetables – cauliflower
• Target: Downy Mildew (caused by Hyaloperonospora brassicae) in propagated brassica crops
• Period: May-July 2018

Take home message

Infinito and Proplant were the most effective approved products in the trial.

Infinito combines two modes of action and is therefore a good choice of product.

Paraat should be used with caution.

Some of the close to market alternatives tested show good potential for disease control and possible approval in the near future.

Trial summary

This trial aimed to identify the best products to control brassica downy mildew. It tested products already approved for use and some alternative products.

Hyaloperonospora brassicae can cause stunting and reduced quality of transplants of crops.

Infection in cauliflowers causes discolouration in the curds. In cabbage and Brussels sprouts lesions may penetrate into several leaf layers causing reduced crop quality.

The pathogen has a wide brassica host range and can infect quickly, as long as leaf surfaces are wet; such as in irrigated glasshouse propagation crops.

The year-round production of transplants enables the continual spread of spores to young crops.

Growers have some approved products available to them, but most of these fall into the same FRAC group which is a cause for concern.

Conclusions

• All products tested were crop-safe during the life of the trial.
• The standard product (Paraat) did not perform well in this trial, potentially due to pathogen resistance, but three other approved products (Infinito, Proplant and Previcur Energy) all significantly reduced downy mildew symptoms.
• One product (AHDB 9880) appeared to increase plant susceptibility to disease, giving higher levels of leaf spotting than the untreated.
• Two products (AHDB 9939 and AHDB 9883) are already approved on other crops in the UK and gave good control of disease symptoms, whilst two novel products (AHDB 9962 and AHDB 9879) also significantly reduced disease levels.

Band spray herbicide screening: 

• AHDB 9875 and AHDB 9999 would be useful additions pre-planting, and AHDB 9999 may bring charlock control
• AHDB 9875, AHDB 9887 and AHDB 9890 applied post-planting could improve weed control and possibilities for authorisation should be investigated
• AHDB 9898 appears safe and effective when applied by band sprayer and when combined with current commercial standards such as pendimethalin, metazachlor and clomazone
• Use of band spraying allows commercial standard products to be applied at maximum authorised rates, increasing efficacy while minimising crop damage
• This is the first time many of these products have been trialled in brassicas and therefore further evaluation would be required before a full understanding of crop safety is known

Pre-planting trials:

AHDB9999, AHDB9987, AHDB9875, AHDB9917, and AHDB9994 are promising products for weed control in cauliflower and were shown in this trial to be safe and effective as pre-planting herbicide treatments. EAMU authorisations for pre-planting use of any of these five products in cauliflower would help growers improve weed control.

Post-planting trials: 

Unfortunately due to confounding environmental factors, no conclusions or messages could be drawn from the trial and further research is required. 

• Crop group: Brassicas
• Target: Cabbage aphid and peach potato aphid
• Period: Aug – Nov 2019

Foliar aphids on leafy brassicas have been successfully controlled in the past with neonicotinoid seed treatments (imidacloprid and thiamethoxam) and a sowing-time “Phytodrip” treatment (thiamethoxam), but approval for all of these treatments has been revoked. A number of alternative treatments were identified as possible replacements for neonicotinoids in a trial on lettuce (SP36) and it is these treatments that were taken forward for testing in brassicas.

Five sowing-time treatments have been identified as possible alternatives to neonicotinoid insecticides.

 Aphid control

• Crops: Carrots, lettuce, brassicas
• Target: Myzus persicae, Brevicoryne brassicae, Cavariella aegopodii, Nasonovia ribisnigri
• Period: Dec 2017 – March 2019

Conclusions

Evaluation of a range of insecticide and bio-insecticide treatments for their efficacy against four species of aphid infesting vegetable and salad crops.

The main study showed that a number of ‘novel’ insecticides and a few bio-insecticides were effective against one or more species of aphid. Some of the insecticides showed good persistence. The study also highlighted the importance of product formulation and adjuvants in increasing levels of control.

The additional study showed that a number of products were effective as foliar sprays and that some of them may also control foliage aphids when applied as phytodrip treatments, although it would obviously be advisable to test such treatments in the field and to evaluate the persistence of such treatments.