STINKING MAYWEED

Anthemis cotula

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DESCRIPTION

Stinking mayweed is an erect, bushy annual weed that mainly germinates in the spring. It germinates particularly strongly when soils are cultivated in spring for pasture renewal or for cropping.

Its most distinctive recognition feature is its white and yellow daisy-like flower, and it is often confused with other species with similar flowers and/or foliage, in particular scentless chamomile. However, stinking mayweed differs in that it (unsurprisingly) has a very strong smell when crushed or rubbed.

Stinking mayweed grows to about 40cm in height.  The leaves are feathery and dark green, up to 8cm long and are divided three times into awl-shaped segments.

Distribution is throughout the North Island and the upper half of the South Island.

The weed is common in spring-sown crops and also in spring pastures of low density as well as new pasture. Once the sward thickens and strengthens, stinking mayweed will usually be naturally reduced or removed from the pasture. It also grows commonly in locations like roadsides, farmyards, holding paddocks and waste ground.

Stock will generally avoid eating stinking mayweed as well as adjacent pasture, but if lactating cows do eat it, noticeable tainting of the milk can occur.

PASTURE MANAGEMENT CONTROL 

In pastures, stinking mayweed will eventually by itself once it flowers because it is an annual species, and management of the pasture should endeavour to improve density in the following late winter to early spring period, to prevent the weed establishing again.

HERBICIDES TO CONTROL STINKING MAYWEED

Stinking mayweed is NOT well controlled by the more common broadcast selective herbicides for pasture use. Rainbow & Brown MCPA750, MCPB and WHACK – 2,4-D 800 are all largely ineffective against it, although WHACK – 2,4-D 800 can be used on seedlings in cereal crops with some success.

Spray Herbicides to Kill Stinking Mayweed in Pasture

• Decision applied at 65g/Ha via a boom sprayer, plus either 500ml BioWet Spray Oil (preferred) or 200ml SuperWetter per 100L water. This option is not damaging to pasture grasses or clover.
• Ranger Herbicide used at 20g per hectare applied by boom spray or at 1g/10L by knapsack for hand spraying.

Both Ranger Herbicide and Decision are best applied at the seedling stage of the weed and both are much less effective as the plant matures. 

• Dicamba 500 Select - 100ml plus 260ml Rainbow & Brown MCPA750 in 100L water per hectare.
• Dicamba 500 Select - 120-140ml plus 535ml WHACK – 2,4-D 800 per 100L water per hectare.
• clopyralid 300g/L  herbicide applied at 25ml per 10L water makes an excellent spot spray treatment.  Note Rainbow & Brown no longer offera clopyralid product.

Note:  clopyralid 300g/L  is damaging to clovers. Ranger will result in some temporary yellowing and check in pasture vigour, but it will quickly recover. Rainbow & Brown MCPA750 and WHACK – 2,4-D 800 will knock clover back. Dicamba 500 Select will kill clover.

Herbicide sprays to Kill Stinking Mayweed in Cereal Crops

• Dicamba 500 Select – use 140-280ml plus 1.0L of Rainbow & Brown MCPA750 in 100-200L water per hectare.
• clopyralid 300g/L  herbicide applied at 1L per hectare by boom spray to actively growing plants. Note Rainbow & Brown no longer offera clopyralid product.