Topic: Garlic Questions

[busy_lizzie]

One of our plotholders is growing garlic in her plot, that was planted in October, and has noticed that the tops of the leaves have gone yellow.  I wondered if this shows some sort of deficiency in her soil, but I said I would ask you guys, knowing what experts you all are. Thanks if anybody can give some advice.  :-* busy_lizzie     

[debster]

there was a post about this really recently and i seem to remember that it was quite normal that everyones is doing it

[Thegoodlife]

could be many things the minor one being a nitrogen difficency or it could be a little mildew which i would say it is with the weather the way it is ,have a read below of other problems.

Garlic Rot
Rot is probably the most common garlic disease. There are two frequently encountered rots:
Basal Rot (Fusarium Oxysporum)
Basal rot is a slow developing condition. Affected garlic plants show gradual yellowing and leaf dieback. There is sometimes a white fungal growth visible at the base of an infected bulb leading to the bulb rotting. Symptoms continue to get worse even after harvesting. Basal rot is favoured by higher temperatures and hence more common in warmer climates.

Downy Mildew (Peronospora Destructor)
Downy mildew can be recognised by an off-white, sometimes slightly purple, furry growth on the leaves of the garlic plant. The leaves go on to yellow then collapse. Since downy mildew is airborne, patterns of yellowing often follow prevailing wind directions in a large crop. Downy mildew can kill young plants and causes stunting in older ones.


Nematodes
The primary nematode of concern for garlic growers is the stem and bulb nematode. Invasion of the stem tissue occurs first, causing stunting, twisted, and pale leaves, usually followed by rotting of the lower stem and base of the bulb. In severely infested fields, young plants become enlarged and deformed and frequently die. The nematodes are primarily located in infected tissue, so to control this pest, infected plants should be removed by digging and then burned. Other control measures include planting clean seed stock, elimination of volunteer garlic and onions, and proper rotation. Do not plant garlic following any member of the onion family, or alternate hosts such as pea, parsley, celery, and salsify.

 

Diseases
Most garlic diseases are either soil- or seed-borne and usually can be controlled with proper rotation and planting disease-free seed. The most common diseases include:

White rot (Fig. 23)

A major disease of commercial garlic grown in California and other areas of allium production. The organism is most active when the temperature is cool (less than 75 °F). In northern climates it usually attacks in the spring. Symptoms include premature yellowing and dying of older leaves, stunting, and leaf tipburn, followed by destruction of the root system, shoot dieback, and rotting of the bulb. Control by rotating out of allium crops for many years (white rot has been know to persist in soil for ten years), destroying infected tissue, and planting disease-free seed stock.

 



Fig 21. Foliar symptoms of Fusarium

The fungus is present in all soils and is usually considered a secondary invader because it attacks plants already weakened by insects, mechanical damage, or other diseases. Fusarium is most active at high temperatures. Symptoms are similar to white rot, except disease progression is much slower and death of the plant may not occur. Bulbs infected with Fusarium may decay further in storage.(Fig 21). This disease is controlled by proper crop rotation with non-susceptible crops for four years, removal of infected plants, and planting disease-free seed.  is a disease which attacks the basal plate region and the roots. The soil-borne pathogen invades the roots, resulting in empty, tan-colored, non-functional roots. The basal plate region may develop a pinkish growth of mycelium. First visual symptoms are often the yellowing of the tip and dieback of the shoot during the spring. Warm soil temperatures and high soil moisture promote disease development. Since the Fusarium inoculum remains as dormant spores in the soil or on plant residue, crop rotation with crops not belonging to the Allium genus (e.g., garlic, onions, shallots, leeks, chives) is recommended ( Bodnar et al., 1998

 

Pink root

Symptoms of this disease occur primarily in warm weather (>75 °F). The fungus infects the roots, causing them to turn pink, followed by root dieback. New roots are formed which also become infected. Aboveground symptoms include leaf tipburn. Control of this disease is by using at least a three- to four-year rotation without allium.

Botrytis

This fungus attacks garlic leaves following periods of warm, wet weather and bulbs in storage. Symptoms include water-soaked stems, which is why the disease is often called "neckrot." In severe infections, the bulbs may rot. In mild infections, the disease may not be noticed during the season, but may attack the bulb during storage. Control this disease by promoting air movement through the field so that foliage does not remain wet. Rapid drying during harvest, followed by good aeration during storage, will also minimize the problem. Use planting stock free of the disease.

Penicillin mould is a main cause of decay of garlic in storage. The disease appears as masses of blue-green spores usually first seen at the base of the bulb. The primary source of inoculum is diseased bulbs used for planting material. When diseased bulbs are cracked the air-borne spores readily come in contact with healthy cloves. Wounded cloves are particularly susceptible to the disease. Often cloves infected with Penicillin become infected with secondary organisms such as bacteria and other fungi, masking the original pathogen. Clove rot and reduced plant stands are often the result of planting infected cloves. Surviving plants which emerge appear weak and yellow. Warm temperatures of 22-25 °C are optimum for spore germination and disease development. Planting garlic too early in late summer when soil temperatures are high may increase the severity of clove rot. Irrigation may be beneficial, as high soil moisture appears to suppress clove decay ( Bodnar et al., 1998).

Penicillium is both a field and storage disease. Plants from infected cloves planted in the fall will often emerge in the spring, turn yellow, and then die. A blue-green color is observed on cloves in soil and in storage. When conditions are optimum for rapid emergence, the plant may outgrow the disease. Air-borne spores spread the disease. If a bulb is infected, do not use the cloves for planting stock. Wash hands after touching the bulb and avoid bruising or wounding stored bulbs. Prevent the disease by planting clean stock.

Rust (Fig. 24)

Until recently, this fungus was considered to be of minor importance in garlic production. However, recent outbreaks in California have reduced crop yields by up to 75 percent in some fields. Initial symptoms occur on the foliage and stem as small, white flecks that develop into orange spots (spores) or pustules. The bulbs become shrunken and deformed. Heavily infected plants may turn yellow and die. Conditions favorable for disease development include high humidity and low rainfall and a temperature between 45 and 55 °F. Disease incidence is highest in stressed plants. To reduce infection potential, use healthy seed in well-drained soil. Rotate with non-allium crops. Registered preventive fungicides may be the only method of control in situations where the disease potential/incidence is high. Varietal resistance has not been reported.

Viruses

Because garlic is clonally propagated, almost all planting stock is infected with some type of virus. The viruses are usually mild and do not seriously affect yield, and may even impart desirable characteristics in some varieties. One exception is onion yellow dwarf virus, which can cause severe mosaic in combination with other viruses. Any plants exhibiting severe mosaic symptoms should be rouged out. Tissue culture has been shown to be effective in producing "virus-free" garlic and is now used extensively for commercial plantings in California. Most of the garlic purchased from seed catalogs and other garlic growers contains some virus.

Virtually all sources of garlic contain viruses. Fortunately, most of these viruses in garlic are latent. Latent garlic viruses may not become visible or reduce yields until the garlic plant is stressed or growth interrupted. The most common symptoms of virus infection are colour changes of the leaves. These include mosaics, flecking, streaking and mottling. Leaf shape distortion may also occur. Aphids are one vector capable of transmitting some viruses from infected to healthy plants. Control of virus diseases is achieved through a combination of planting healthy cloves, reducing aphid populations, proper fertility and water management during the growing season ( Bodnar et al., 1998).

 

Pests : All pests that attack onions will affect garlic crops. The most significant pest is likely to be nematodes (eelworms) which attack the roots and bulbs. Bulbs should be inspected before planting to ensure cloves are nematode-free and if possible dusted with nematicidal powder immediately prior to planting. Thrips and onion maggot are two other potentially serious pests



my garlic is ok at present as im one a sandy soil wich dries out very quick, but last june when all that weather hit us my garlic did show signs of yellow leafs & then tips of the leaf dying of still got a great crop, this year i have autumn sown & this weekend i will be trying spring sown garlic to see how it goes ;D
 



 

[tim]

Not saying it's right, but mine always tends to do this at this time. No problem with result.

[busy_lizzie]

Wow!! Thanks everyone, that is a brilliant response. TGL, what a lot of research -  thanks so much! Tim, thanks, they actually look a bit like yours so hopefully not too much of a problem. I will let her know. Proud of you all!  :-* busy_lizzie

[goodlife]

You will find that after giving the garlic a feed of chicken manure pellets they will perk up and start throwing new green growth without yellow tips...it is just winter growth that has it..

[cambourne7]

ah must try that myself.

My garlic has started to yellow i felt down and there is not much of a bulb yet more like spring onion ;( not sure if i wend down long enough of if thats what they should be like.

[goodlife]

My garlic has started to yellow i felt down and there is not much of a bulb yet more like spring onion ;( not sure if i wend down long enough of if thats what they should be like.

I'm sure your garlic is fine..they do not need to be in deep..but as they start to grow now they do need extra feed..handfull of "chicken" pellets per square metre once a month untill early summer..and then leave them to harden off for few weeks before lifting them up....thats all..and you'll end up with good size garlic bulbs...that's if you planted big enough cloves to start with..

[cambourne7]

yippie  :D

I will head down with the chicken poop next week when i am back up on the site.

Is it worth putting some on my spud bed ?

[goodlife]

I would not use fresh stuff..too strong..If you have composted droppings fine but I use chicken manure pellets as it is easier to handle and you know how much to give..over feeding is not good neither..
Yes you can give pellets to potatoes too, but I would wait a bit longer untill any danger of frost is passed...too much lush growth too early..and you are asking for the trouble..

[cambourne7]

sorry yes these are the pellets you buy in the diy shops.

Spuds only went in yesterday so they should be ok from the last of the frosts.

[Ant]

when we asked this question a few weeks back, it was suggested it was a nitrogen deficiency.

Stuck some chicken pellets down last week and the garlic has really perked up.  :) Haven't noticed anything else untoward with the foliage but don't know whats going on beneath the surface  :-\

[goodlife]

Stuck some chicken pellets down last week and the garlic has really perked up.  :) Haven't noticed anything else untoward with the foliage but don't know whats going on beneath the surface  :-\

Trust me..your garlic is fine ..even beneath the surface..
Your garlic needs to make more top growth before the bulb itself start to develop. It is pretty much the last 8 weeks before they are ready that the bulb really swell and start to divide into cloves...
Growth is only starting to happen..soon you notice some changes...

[Ant]

thanks Goodlife  :D

This is our first year growing garlic so not sure what to expect/

[Deb P]

My garlic today, the Marco (foreground) seems to be doing the best. All fed with pelleted chicken manure a week or so ago. Seem to be on course for the time of year so far.... ;D

[manicscousers]

ours a week ago, just fed so will see what happens  ;D

[Robert_Brenchley]

Mine look very much the same.

[goodlife]

Garlic in both pics look fine..
Dep..yours look like you are going to get really good size bulbs.
Manics..yours fine too..little behind but they will catch..remember to feed again in 3 weeks time....
 ;D ;D ;D