Sunday, August 4, 2013

Gardener's watch for plant invaders By Harrison Wood, master gardener

All this rain and warm weather that we're having has many advantages; the plants are going to begin to explode. 

And so are some of the diseases like downy and powdery mildew.  They will say thank you for such high humidity and they will also explode, attacking everything and anything, especially the squashes and the cucumbers along with their close relatives. Ignored diseases of this sort can make short life of what you've planted so as you make your morning forays watch for the first signs.

Powdery mildew, the first and most invasive, is well known to rose growers as the leaves pick up the first signs, which appear as a powdery white coating on the leaf’s surface. Those plants that have been excessively fertilized will be the first to be attacked. The disease damages the plants by attacking the leaves via their natural stomata’s through which they breathe.

Some varieties are resistant so pay attention to the ones that get assaulted first and make note of them in your garden log. To help keep the assault at bay there are a couple of things we can do. When and if we do have to water, do it during late afternoon well before dusk. The disease spreads on water so we need to allow enough time for the leaves to dry off. Another advantage that late afternoon watering has is that it also helps cool the plants off. Cool plants grow much happier as their natural resistance to disease stays intact.

If the disease does get ahead of you, a selective removal of a leaf here and there will help. Remember not to simply discard the spent leaves on the ground or into the compost. Many diseases are soil born so when competing the task, plan on discarding the infected leaves in the trash to be carried far away. Some people argue that the high temperatures in the center of an active compost is high enough to sterilize most diseases and in most cases this is true, but how many of us open our compost piles to put the culprits into natures ovens.

If disease begins or if you've had it in the past, spraying with a natural treatment like Neem oil will go a long way to help, just remember not to apply it during the heat of the day, wait until either after things cool off or as I do, apply first thing in the morning.

While checking your squash and cukes, pumpkins as well, be alert to what may look like white lines on the leaves. When you lift the leaves you may notice that the lines appear on both the top and bottom. Chances are good that what your looking at is an insect called leaf miners that tunnel between the two layers, often doing extensive damage. Once you see them there is actually not much that you can do. The important thing is to note their damage in your garden log so that next season you can get on an early application of Surround too prevent the damage. This year if the leaves are few simply pick them off and send them away with the trash.

Slugs and snails will also take advantage of weather like this so be at the ready. There's a lot we can do to stop them.

Either way it's always better to act proactively rather than when things get out of hand. So as you make your daily walk through do so with open eyes.

The leaf lettuces as well as the other cool weather crops like peas hate this weather so be ready to harvest and enjoy before they're gone.

Plain and simply; keep going.  It will be worth it!

Written by Harrison Wood
Master Gardener
Windham Community Garden

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