Posts Tagged ‘leaves’
Powdery Mildew
Terrie Greco, B.A.; HLT Dip.
Ah yes, the ‘dog days of summer’ are here, and along with the hot humid weather comes a not so attractive disease on your plants called Powdery Mildew.
When this disease starts rearing its ugly head around mid July, it looks like Mother Nature has sprinkled icing sugar on the leaves. Small powdery white spots begin to appear randomly on the leaves of numerous hosts. As the spots become larger, and eventually merge, photosynthesis is reduced; the leaves dry out, turn brown and hang their heads down in shame on the stem of the plant.
Unfortunately, numerous plants succumb to this disease – Sunflowers , Zinnia (Zinnia spp.), Rose Bushes (Rosa spp.) Bee Balm (Monarda spp.) and Lilac (Syringa spp.) – to name just a few.
Here is a picture to help you identify Powdery Mildew:
Powdery Mildew
The fungal spores are found in the soil and spread by water droplets, so although it’s impossible to stop rainfall, you can practice a few good cultural habits to minimize the spread of Powdery Mildew throughout the garden. Here are a few suggestions to help you combat Powdery Mildew:
- See to adequate spacing between plants allows air to circulate in the garden and leaves will dry off more quickly after rainfall or watering.
- Minimize overhead watering if you can.
- Use garden mulch to reduce water splash.
- Remove leaves when the first signs of Powdery Mildew appear.
- Do not compost foliage with Powdery Mildew or this disease will be back again in full force next summer.
In her book ECOLOGICAL GARDENING, Marjorie Harris provides additional tips to deal with Powdery Mildew such as using baking soda and/or Epsom salts.
In and of itself, this disease does not kill plants, but leaves them weaker over time.
Below are a couple of useful links with some photos of Powdery Mildew.
http://www.omafra.gov.on.ca/IPM/english/tomatoes/diseases-and-disorders/powdery-mildew.html
http://www.umassvegetable.org/soil_crop_pest_mgt/disease_mgt/tomato_powdery_mildew.html
Caterpillar Pictures
Terrie Greco, B.A.; HLT Dip.
I got a lot of positive feedback on last week’s “Caterpillar Brigade” post. I also received numerous emails requesting photographs. So I put some together here for you:
Image 1 – Malacosoma americanum: Eastern Tent Caterpillar ‘tent’ Webs
Note that the Eastern Tent Caterpillar always produces a silken web in the forks of tree branches. During the day, the caterpillar leaves the nest to feed and returns at night. The nests grow larger as the caterpillars mature and need more room. Constant home renovation!
Photo courtesy of John Himmelman, childrens author, illustrator and naturalist
Image 2 – Malacosoma americanum: Eastern Tent Caterpillar Egg Bands
Note that compared to the Forest Tent Caterpillar egg bands, the edges are more rounded.
Photo courtesy of Brian Kunkel, University of Delaware, www.bugwood.org
Image 3 – Malacosoma americanum: Eastern Tent Caterpillar Mature Larva
Note that the Eastern Tent Caterpillar has a white stripe down the back, blue spots on either side and plenty of hairs (setae).
Photo courtesy of David Cappaert, Michigan State University, www.bugwood.org
Image 4 – Malacosoma americanum: Eastern Tent Caterpillar Adult Moth
Note the white forewing stripes on Estern Tent Caterpillar compared to the darkish stripes on Forest Tent Caterpillar. The adult female of the Eastern Tent lays eggs in early to mid summer in a band around twigs. The eggs over winter and hatch in early spring just before bud burst. This pest prefers apples, crabapples and cherry trees.
Photo courtesy of John Himmelman, author, illustrator and naturalist
Image 5 – Malacosoma disstria: Forest Tent Caterpillar egg band on twig. Pruning off the egg bands in spring will do much to reduce the population. Compared to Eastern Tent Caterpillar egg bands, the edges of the egg band is square rather than rounded.
Photo courtesy of Thérèse Arcand, Natural Resources Canada, Canadian Forest Service
Image 6 – Malacosoma disstria: Forest Tent Caterpillar mature larva – This caterpillar can be identified by the white ‘keyhole’ or ‘footprint’ shaped spots down the back and a blue stripe on either side of the body.
Photo courtesy of John Himmelman, author, illustrator and naturalist
Image 7 – Malacosoma disstria: Forest Tent Caterpillar Female Adult – The adult female moth lays hundreds of eggs on a small band around tree twigs in mid-summer. The eggs over winter and hatch in the spring. Note the dark beige coloured wings with the two dark downward facingbands on the forewings.
Photo courtesy of John Himmelman , author, illustrator and naturalist
Image 8 – Hyphantria cunea: Fall Webworm Tents – Compared to the webs of the Eastern Tent Caterpillar, which are produced in the forks of trees, Fall Webworm forms silken tents at the ends of branches. The larva feeds inside the tent, destroying all the foliage in the web before moving to another location on the tree.
Photo courtesy of G. Keith Douce, University of Georgia, www.bugwood.org
Image 9 – Hyphantria cunea: Fall Webworm Larva – The larva are creamy white with prominent black bumps on the body, and extremely hairy. If I were a bird – I would have trouble swallowing this caterpillar!
Photo courtesy of John Himmelman , author, illustrator and naturalist
Image 10 – Hyphantria cunea: Fall Webworm Adult Laying Eggs – The adult female lays a large mass of eggs on the underside of leaves of White Ash, Birch, Willow – to name just a few hosts. The egg masses can easily be missed by a homeowner. The adult is either pure white or has a scattering of small brownish/black markings on the white wings.
Photo courtesy of H C Ellis, University of Georgia, www.bugwood.org
Image 11 – Hyphantria cunea: Fall Webworm Adult –Portrait of a moth…you gotta love that face – and wait – is that hairstyle a mullet??? Joking aside – it’s an amazing photo of a moment in nature captured in time…
Photo courtesy of John Himmelman , author, illustrator and naturalist
We are very grateful to John Himmelman for generously offering permission for the use of his moth photographs on our website. John is a well known childrens author, illustrator and naturalist. Check out his websites below!
The Caterpillar Brigade
Terrie Greco, B.A.; HLT Dip.
When I was a child I found great pleasure in holding what I considered to be a fragile yet comical creature in my hand – the caterpillar. Over the years, I came to realize that caterpillars are programmed for plant destruction. It’s a survival strategy to which allows them to develop into the adult stage as a moth or butterfly and reproduce.
The caterpillars I find most intriguing are categorized as ‘the social caterpillars’ – (see link below for an explanation). They are the:
- Eastern Tent Caterpillar Malacosoma americanum
- Forest Tent Caterpillar Malacosoma disstria
- Fall Webworm Caterpillar Hyphantria cunea
Both Eastern and Forest Tent caterpillars emerge mid-late May from over wintering egg masses found on twigs. Eastern Tent caterpillars will attack crabapples, apples, and cherry trees. Forest Tent caterpillar prefers maples, oaks and birch as host plants. Fall Webworm larva emerge in late August from eggs laid on the undersides of leaves – this pest infests numerous fruit tree species along with elm and willow species.
Defoliation can be severe, and if repeated, can result in the death of the tree. Treatment with Bt (Bacillus thuringiensis) – a natural and safe bacterium – is the best known solution. It has proven over the years to be user-friendly, efficient and safe. One important thing: Bt is much more effective when the larva is small.
Why is Bt more effective on younger larva?
- Bt bacterium produces a crystalline protein toxin that kills the single layer of cells lining a caterpillar gut
- Cells in the younger larva are not multiplying and dividing as rapidly as in older larva – therefore the older larva can effectively ‘heal’ the gut wall and survive the effects of Bt. COOL!
- If Bt has not been effective for you in the past – you probably applied it too late!
Pruning out egg masses and opening webs to natural predators are easy ways to check an infestation before it’s too late – remember folks – effective treatment means catching things early!
This link describes the safety of the product Bt.
http://www.youtube.com/watch?v=7TTS80xyw4A
Excellent instructions and information on the use and application of Bt(Bacillus thuringiensis)
http://www.agf.gov.bc.ca/pesticides/infosheets/bt.pdf
Oh, and don’t forget to check out the following Web site for more info: http://www.bugwood.org/
That Darn Lily Leaf Beetle!
Terrie Greco, B.A.; HLT Dip.
We have an intruder in this country – a bold, brash, bright reddish orange beetle known as the Lily Leaf Beetle (Lilioceris lilii). This beetle hails from Europe and Asia, and was noticed in the Montreal area in the early 1940’s. It has been heading west ever since, leaving a trail of destruction among your favourite Lily plants.
Even if this ‘import’ had natural predators, its habits are so disgusting that even the most self respecting bird avoids it. The larva has a peculiar habit of using its own excrement as a protective cloak. Not an attractive appetizer let alone a main course for any predator. If this wasn’t bad enough, the brightly coloured adult has an uncanny sense of timing. When the adult senses danger, (such as a gardener preparing to pluck it from the leaf) it folds up its six black legs and ‘sky dives’ to the ground – with its black underside facing up. Adventure and camouflage all in one clever ploy!
The burning question – how do we control it? Using Neem oil as a repellent on the leaves shows plenty of promise. Monitoring and handpicking are very effective. Watch for the brightly coloured adults emerging from the soil in late spring and grab them before they find true love! Each female can deposit 400+ eggs – capturing and destroying a few will make a difference. If some beetles end up having a tryst – don’t call yourself gram or gramps yet! Brush off small orange rows of eggs from the underside of leaves before the larval stage emerges. Two or more generations are possible, so be diligent with these recommendations until late August.
Check out the following photographs.
Lily Leaf Beetle .Note the bright red orange body and black head and legs – capture and destroy!!!
Lily Leaf Beetle. Adult females lay small orange cylindrical shaped eggs in neat rows on the underside of Lily leaves in late spring – brush them off with a gloved hand or remove the leaf.
Lily Leaf Beetle larva covered in an ‘excrement cloak’ – gross! Some insects have no manners…
Lily Leaf Beetle. I have removed these leaves to show the eggs and different stages of the larva. Notice the severe destruction of the leaf tissue! These insects have no mercy.
Lily Leaf Beetle. It just goes to show you that this pest can destroy a plant within a few days.
Keep your eyes open in the garden – you never know what’s hiding behind that leaf! Keep reading this blog for more info.