In this tip:
In this post you’ll find a description of some plant diseases and insects that I saw in my garden. I added some photos. Info from internet and my own experience.
In early summer (June) it can happen that “many onion plants in your garden are ill”. See photos and descriptions below.
A1) Onion fly
Leaves of the onion plants are yellow – brown and lie on the garden soil.
In the onions there are maggots of the onion fly. Onion plants will die.
A2) Leaf-miner fly (on onion plants)
Leaves of the onion plants are green and curled.
In the onion you see “eating grooves” and maggots or brown pupae.
The onions will grow to big ones with deviating shape as shown on the photo above.
A3) Help against onion flies and/or leaf miner flies.
- Buy more onion sets.
- Plant only few onion sets in early spring (March and April). In these months, there is big risk of attack by leaf miner flies and/or onion flies.
- But……you can plant “many” onion sets in March and April (early spring) when you put a layer of hay on the soil between and around the small onion plants. Due to the layer of hay, the soil does not dry out so fast. And there is less attack by the onion flies and miner flies. See chapter A5).
- Plant most onion sets in mid spring (May). The leaf miner flies are not active during that time. Putting hay around and between the small onion plants works well too; soil does not dry out fast.
- Harvest the onions in July to September (late summer, early fall). Onions are big enough then. Leaves get yellow and topple and the onions do not grow thicker anymore.
A4) Does it help?
The first row contains onion plants from onion sets that were planted in early spring (April). Many onion plants have been attacked by onion flies or leaf miner flies.
Two rows of onion plants from sets planted at mid spring (May 15). All onion plants look healty. At the end of August (late summer) they have grown into normal sized onions.
Conclusion: onion sets planted in May (mid spring) give a good harvest in August (late summer). And there is little attack by insects.
A5) A layer of hay around and between the onion plants:
When you have planted onion sets in early spring (March, April), you better lay some dry hay or mowed short grass between and around the little onion plants. The soil will not dry out so fast, the onion plants grow well and show less diseases and damage of onion flies or leaf miner flies.
At later planted onion sets, you can also put dry hay between and around the onion plants. That works well too. In short, hay around all onion plants is okay.
A6) Test: planting date and hay around.
To find out when onion flies or leaf miner flies lay their eggs on onion plants, the following experiment has been executed;
- At March 20, one onion set has been planted in the garden soil, in a small furrow.
- Each subsequent day, another onion set was planted in that furrow and thus forming a row. Distance between onions was about 10 cm (4 inch).
- At May 1, the 43th onion set was planted in the garden soil in that row. The row was full then.
- With this experiment, one can determine which onion plants are attacked by flies. So what planting dates are good or bad.
- From the beginning of April on, a thin layer of dry hay has been put around and between the onion plants that were visible. This is done because I have found that dry lawn grass (short hay) on the soil around sown onions shows less attack of flies. Maybe hay (= dried grass) on the soil also helps at onion sets. Hay is for sale in a pet shop and not expensive.
- One year later, the experiment was repeated with 3 rows of onion sets. From March 20 until May 1, each subsequent day 3 sets have been planted. Later on, dry hay has been put between and around small onion plants of 2 rows. In the other row, fresh mowed grass or dry straw has been put around and between the onion plants.
A6b) Results and conclusions:
- No (little) attack by the leaf miner fly or onion fly observed.
- A few plants showed curled leaves.
- Harvest: many big onions and a few small onions.
- Most onion sets grew into big onions (38 out of 43 and 115 out of 129).
- There is little weed between the onion plants. And weed plants are easy to remove (pull out).
- Under the layer of hay the soil does not dry out so fast. The onion plants grow well.
- Putting hay around the onion plants works well against attack by onion fly and leaf miner fly. Even during the “risk period” of the leaf miner fly (March and April).
- In each row with hay around the plants, more and bigger onions grew. So dry hay works better than grass or straw.
- Earlier planted onion sets brought bigger (heavier) onions than later planted ones.
- The last 6 planted onions in each row showed no attack by flies.
More and detailed info at chapter E)# of tip 5) Planting onions in a small furrow.
B1) Curled leaves
In early summer (June) some leek plants can have curled leaves. Similar to the curled leaves of the onions caused by the leaf miner fly.
There are no maggots or pupae. Only white eating grooves in the green leaves. As indicated between the 2 red arrows. This attack is caused by leaf miner flies.
Help against curled leaves:
- Do not plant out the leeks that have been attacked.
- Sow more leek seeds so you have more leeks to plant out later.
- Try out if liquid nettle manure spraying helps.
- More space between the leek plants. So a bigger distance between leek seeds or extra thinning out small leek plants.
- Grow small leeks in your garden under a tunnel greenhouse with ultra fine mesh netting at both ends of the tunnel.
B2) Purple spots on leaves
In autum, leaves of leek plants can look like this.
This disease is called purple blotch. The leaves have purple spots. The leaves have “dead ends”. After removing the coloured leaves, the plants are okay.
Info on the internet, see this site
This disease occures after a cold and wet weather period. Maybe after planting leeks too deep or too much manure added.
The disease occured in my garden (for the very first time in more than 25 years) in 2012.
- Internet: Shallow planting. Adding less manure. Putting garden earth around the plants not until the plants are big.
- My experience: Put leek plants in round holes (diameter 6 cm, 2.4 inch) in the garden soil. Keep the holes “open” for a long time. This results in no risk or little risk of this disease.
B3) Brown pupae (leaf miner fly)
Brown pupae in leeks frequently occurs. Almost every veggie gardener has seen the brown “things” on and under the leafs of a leek. There are cracks and tears in the outer white leaves of a leek. The edges of the cracks are light brown. In this chapter you find an extensive description about this attack (and how to reduce this attack).
In late autumn or early winter there can be brown pupae when harvesting leek. See photos below.
Typical for this disease (see photos above):
- Some (white) parts of the leek plant have long “cracks” or “tears” with light brown edges.
- Eating tracks are visible on leaves and white parts.
- Pupae hide in leaves or at other parts of the plant.
- Pupae are about 4 mm long (1/6 inch) and dark or light brown. On the lowest photo at the right you see a maggot (or small pupae) that is somewhat smaller.
- Sometimes there are some maggots on the leek. This maggot is still eating leek material. It is not yet ready to transform into a brown coloured pupa. The lowest photo with a wooden cocktail pick shows the size of the maggot.
These pupae and maggots are children of the “allium leaf miner flies” also called “leaf miner flies”. You can find info about this disease on the internet, for example on this site .
Leaf miner flies lay their eggs on the leaves of the leek plants in spring (early March to early May). Eggs –> white maggots –> brown puppae. The pupae “rest” until the end of summer. During this rest period, the pupae are in the leek plants (or somewhere else, such as in the garden soil or in leaves of leek or in compost).
Help against leaf miner flies
- In spring
In spring leek plants can grow in the garden soil under a greenhous tunnel. To keep miner leaf flies away, you can do as follows;
- Leek plants in the garden soil at the end of October (mid autumn), after trimming and/or laying hay on.
- On the left side photo there are leeks without hay. Most leek plants have been trimmed weekly and show short leaves. Leek plants at the far left side of the photo have been trimmed once, at the beginning of September (late summer). These leeks have long leaves now.
- At the right side photo you see weekly trimmed leeks, with or without hay on.
From November (mid fall) on, leek has been harvested.
On the photo above you see harvested leeks. There are 3 groups of leek. Under each group of leeks there is an indication; Nothing, Trimmed or Trimmed and hay on. Below an explanation of the groups. Click on the photo for wide screen.
- At the left side of the photo there are leeks that have grown “normally”; no trimming and no hay on (group “Nothing”).
- In the middle you see leeks that have been trimmed weekly (group “Trimmed”).
- At the right side there are leeks that have been trimmed weekly and that had hay on the trimmed leaves. (group “Trimmed and hay on”).
- At 6 leeks of the group “Nothing”, all pupae and maggots have been collected, see photo above. The 6 “Nothing” leeks contained 4 maggots and 10 pupae in total.
- You better crush the pupae and maggots (to prevent new flies from hatching).
Later on, more leeks of the group “Nothing” have been harvested and cleaned. See photos below.
Later on, 14 more leeks of the group “Trimmed” have been harvested and cleaned. These leeks are rather thin compared to the other leeks. See photos below.
One week later, 5 more leeks of the group “Trimmed and hay on” were harvested and cleaned. See photos below.
At some potatoes I see brown spots (warts).
After peeling the potatoe looks normal.
This can be caused by mixing (too much) agricultural lime through the garden earth. Potatoes grow well in slightly acidic soil.
Help: Do not add agricultural lime in the garden soil.
This disease is caused by larvas of the the cabbage gall midge. Info on the internet is here . This midge lays eggs on cabbage plants that grow at sheltered, calm places in the garden. My attacked cauliflowers grew next to the stake beans.
Plant the cabbages on windy places in the garden.
E1) Brown spot at lower side of tomato
Green or ripe tomatoes can have a brown spot at the lower side (opposite the crown). This is called blossom end rot and is caused by water shortage. The tomato plant is not ill, so keep the plant in the soil. You can throw the tomato in a compost container or cut away the brown material.
Add a little water to the plants dayly. Better add 1 small beaker of water each day than much water once a week.
E2) Crack in tomato
When much rain water falls on the tomato plants and/or when you water the tomatoes too much, you can get tomatoes with cracks.
Tomatoes on the plants can get cracks even before they are ripe.
When you add a little water to the tomato plant each day, there is less risk of cracks in the tomatoes. Watering goes well when using a bucket and a small beaker. You better pour 1 small beaker of water at each plant daily. That’s better than adding a big amount of water once a week.
E3) Dark spots on fruits, stems and leaves
It is possible that you get brown coloured tomatoes and brown leaves at the plants. This plant disease is called Phytophtora.
It is probably caused by rainy weather during late summer, early autumn (August, September). Cold rain water on the plants and fruits causes the plants and tomatoes to get brown (or rot).
Below some photos:
Tomatoes under a roof in my backyard garden at early autumn (September 1). As you see there are a lot of “good-looking” healthy tomatoes. I counted more than 100 tomatoes hanging on 11 plants. Only 10 tomatoes hanging under the roof have brown spots. And some plants have leaves with brown spots.
When there is no roof over the tomato plants, tomatoes can get brown spots and rot during “a rainy summer and a rainy, cold autumn”.
Tomatoes in my allotment garden. Under the roof there is plastic foil to catch dew drops, so they do not fall on the tomato plants.
At dry weather the side foil is folded down.
During heavy rain the side foil is fixed to the roof.
With side foil fixed, the roof is still airy thanks to openings above and below the side foil.
F)# Witloof (Chicory)
These witloof heads don’t look healty. There are brown, sticky, short outer leaves. On the heads you see spots.
This witloof has grown on chicory roots with non removed outer leaves. Maybe the compost in the flower pot was too moist during witloof forcing too.
The left side photo shows the chicory roots before witloof forcing. On the right side photo you see chicory roots with brown short outer leaves right after breaking off the heads.
Always cut or break away the outer leaves of chicory roots before forcing witloof heads. More info in chapter N2) of tip 24) Growing chicory .
Winter carrots can have deep cracks.
- Regularly water the garden soil around the carrots.
- Lay hay or straw around the plants on the soil; the garden soil does not dry out fast.
Preparing for a meal:
You don’t have to throw these carrots on the compost heap.
Use a kitchen knife to cut the cracked carrot in good pieces. Prepare the pieces of winter carrot in the kitchen.