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Tuesday, May 3, 2016

Rain in the Desert Can Be A Bad Thing

You are probably thinking this rainy weather was a good thing. It is and it isn’t. Let’s talk about some of the problems this rain has created for us now and over the next month.
            Expect an explosion of disease problems. Look for diseases on tomatoes, Asian pears, some European pairs like Bartlett and even some apples.
Tomatoes sprawling on the ground frequently have a higher percentage of fruit that rot than those kept off the ground. One popular way around this is the use of tomato cages.
'Early Girl' tomato crowded in a tomato cage
Tomato cages keep tomato vines from laying on the ground and suspend fruit in the air where they are less likely to rot. The bad thing about tomato cages is they force all growth into a dense, upright tangled mess.
The center of this tangled mess, if left to grow without human intervention, is dark with very poor air movement. Tomato diseases love this environment particularly if it is wet and humid. Because of poor air movement and shade, the center of these plants tend to remain humid and dark.
The beginning of Early Blight disease on tomato
Plant diseases love moisture, shady areas and older leaves, particularly if the plants have not been fed. If tomato plants growing in cages are wet from overhead sprays or extended periods of rainy weather, diseases can be a big problem.
Tomato plants grown in cages should have suckers removed from leaf crotches as they are growing. This thins the plant and the remaining leaves get more sunlight and better air circulation. Tomato fungicides should be applied before things get really bad.

            I am predicting there will be an explosion of fireblight, a bacterial disease, on Asian pears, many European pairs and some apples. Asian pears are the most susceptible but look for it on European pairs like Bartlett and even some apples. You might see it also on pyracantha and ornamental pear.
Fireblight in May
            This virulent disease enters susceptible trees through the flowers, blown around during wet, rainy weather. Pears and apples were flowering when the first of these recent rains occurred. That was the clue that something was likely to occur this year.
Blackening and hook commonly seen with a fireblight infection
It takes time for fireblight to incubate inside the flowers and spread so signs of this disease will begin over the next couple of weeks. The first sign is the blackening and death of flowers and fruit and “hooking” of new growth. This disease spreads very rapidly and, if not controlled early, kills branches and possibly later, the entire tree.
Advanced stage of a fireblight infection
When symptoms are first seen use a sanitized pruning shears to remove the infected area 10 to 12 inches below where it is seen. Always sanitize pruning shears with alcohol, bleach or Pine-Sol after each cut. Bleach rusts steel so oil the shears soon after using it. Bag the infected plant parts and put them immediately in the trash. Do not compost it.

It is normal to see mushrooms coming from wood mulch and newly planted lawns after rains. Mushrooms are a close relative to fungal diseases and are not inherently bad. Mushrooms are signs that decomposers are at work and feeding off of decaying wood. They are generally not safe to eat so knock them over with a rake when you see them and don’t worry that these indicate plant disease.
Mushrooms popping up in wood mulch after rain

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