Late blight weather predicted for August in midwest, NE

[b54red]

Originally Posted by KarenO

I think trying to prevent fungal infection is certainly worthwhile but once late blight is actually in a garden, I think home gardeners spraying this and that ineffective treatment and trying to salvage doomed and dying plants contributes to spread most certainly. If everyone pulled and properly disposed of late blight infected plants at first sight the disease would not be as rampant and fast spreading. It will likely never happen but if it did, the problem would diminish significantly.
I think home gardeners like my self should try to help by being vigilant and learning what it looks like from first signs of infection. My livelihood does not depend on my garden but ommercial producers' do.
Surprises me how many serious gardeners don't have the ability to diagnose and differentiate between really obvious diseases such as Early and late blight in the garden. Education is key and the information is out there. Bottom line: nothing kills late blight once the infection is present. Pulling and bagging and disposing of infected plants is the best course of action to reduce spread not only in our own gardens but every farm and garden within a ten mile radius.

KarenO

You are certainly right about not recognizing diseases early enough. Part of the reason for that is most gardeners don't see some of these diseases often enough to realize what is happening until it is too late. The first time I got late blight I had been gardening for over 10 years and had never seen it so I had no idea what to do. I sprayed all the regular fungicides available to me at the time with absolutely no positive results. By the time I found out what I was dealing with my tomatoes were history. The second time it hit my tomatoes I did recognize it but still I was too late combating it with the diluted bleach spray to prevent significant loses. The third time my tomatoes were hit by LB I immediately started a very thorough spraying with the bleach spray every day for three days in a row and really stopped it cold. I think that by the time symptoms are visible you only have a very short time to react or it will spread and be unstoppable.

Bill

[brownrexx]

Late Blight spores are spread through the air and you can get LB even if you never buy a plant from a store. It happens when you have humid but cool weather late in the season in my area. This is why I try to plant as early as possible because LB usually happens in August but not every year. It seems to depend on weather conditions.

The first time I experienced it, I tried to cut off every infected leaf and even pulled out a few plants and removed them from the area but to no avail. All of my tomato plants died within a week and the fruits developed big ugly brown areas too so they were worthless.

Now if I see LB, I assume that the plant is doomed and get rid of it although so far LB spores are not able to overwinter in my area.

[RayR]

Originally Posted by FredB

I've read that late blight doesn't overwinter as far north as where I live (central Indiana). In over 20 years of growing tomatoes I've only had late blight once. That year I bought a plant from one of the big box hardware chains. The purchased plant turned black followed by a wave of death-to-tomatoes expanding in a circle around the infected plant. Since then, I've never purchased plants from a big-box store and never had late blight.

LB overwinters just fine up North on infected potato tubers underground. All the LB alerts in NYS are from infected potato plants in recent years.

[Labradors2]

How low is low for cold temps (alternating with rain) that can cause Late Blight? We're due to dip to 53F overnight tonight with showers on and off. It's been a wet season and my plants already have Septoria and Early Blight and I have stripped a pile of leaves

Linda

[gorbelly]

It doesn't overwinter, but it spreads extremely easily on the wind. YOU may not purchase plants anymore, but it's likely that there are people within radius of several miles of you that do. Chester County in PA, which is right next door to me, is an area where LB does not overwinter, but it has late blight now, reported on a small farm.

The LB disaster of 2009 was basically due to a combination of perfect LB weather and infected transplants that had been distributed far and wide via stores.

LB can overwinter by forming oospores that survive without a live host and can survive freezing, but it requires 2 mating types to enter a sexual cycle, and that almost never happens in North America.

Originally Posted by RayR

LB overwinters just fine up North on infected potato tubers underground. All the LB alerts in NYS are from infected potato plants in recent years.

^This as well. It's not so much the freezing as the fact that, in the north, freezing kills the live hosts that P. infestans needs. But tubers can stay alive under the ground to keep LB alive.

[gorbelly]

Originally Posted by Labradors2

How low is low for cold temps (alternating with rain) that can cause Late Blight? We're due to dip to 53F overnight tonight with showers on and off. It's been a wet season and my plants already have Septoria and Early Blight and I have stripped a pile of leaves

Linda

Linda, I'd definitely look into seeing whether there's some kind of alert system through whatever equivalent you have of a county extension in your area. It doesn't have to be that cool for LB. Just cooler and wetter than usual East Coast USA summer temps, which are usually high 80s/low 90s and fairly dry this time of year. Now they've dropped into the low 80s/high 70s with daily thunderstorms and/or intermittent showers, and it's causing problems.

[Labradors2]

Thanks Gorbelly. There is some kind of system here. I stumbled across it once before (a few years ago) through Google so I'd better go and do a search.....

Linda

[Labradors2]

Yup. It's in Ontario now

Here's a good link on what to look for:
http://blogs.cornell.edu/livegpath/g...o-late-blight/

Off to take another look at my plants.....

Linda

[b54red]

Linda those pictures bring back some sad memories for me. If anyone has ever had Gray Mold on a plant then they have a basic understanding of what Late Blight looks like. Even though they look similar they act very different usually. Gray Mold is usually much slower in infecting nearby plants and it almost always starts at the bottom and deep in the shady portion of the plant first. Late Blight can pop up anywhere but for me it has usually started in the top half of the plants after rain. At least that is where I have usually seen the first symptoms. I don't believe I have ever seen Gray Mold show up first in the top half of a plant, though it can certainly get there quick enough if left untreated.

The fact that they are so similar in appearance is one of the reasons I use the bleach spray to treat Gray Mold. You just can't be sure sometimes that it isn't LB. The bleach spray will quickly wither and dry out leaves affected by either and lessen the chance of spores forming and spreading if used soon enough. Once either disease gets into the plant system neither can be stopped and that is why if I am in doubt I treat right away. It isn't foolproof but it can save a lot of plants if done promptly.

Bill

[Labradors2]

Bill, I had grey mold on a dwarf plant a couple of years ago. I recognized it because it was on the stem. I hacked the whole stem off and the plant survived

I'm considering using the bleach spray on my plants because, hard as I try, I'm not able to get to all the diseased foliage. Next year I won't plant them so close together!

Linda

[b54red]

Originally Posted by Labradors2

Bill, I had grey mold on a dwarf plant a couple of years ago. I recognized it because it was on the stem. I hacked the whole stem off and the plant survived

I'm considering using the bleach spray on my plants because, hard as I try, I'm not able to get to all the diseased foliage. Next year I won't plant them so close together!

Linda

Dense planting and heavy foliage help create the atmosphere that Gray Mold loves. A couple of precautions that you can take that will delay or reduce the incidence of GM is to keep the plant pruned so it is more open and keep a good amount of air space under the plant. Another is to regularly spray with a copper fungicide to prevent and actually control mild outbreaks of GM. Despite frequent and heavy rains all summer I have only had to resort to the diluted bleach spray to stop one bad outbreak of GM so far this season.

If you use the diluted bleach spray make sure to do it late in the evening and hit the undersides of the leaves as well as the mulch under the plants. Don't be surprised if the Gray Mold extends far further up the plant than you initially thought. The bleach spray will literally shrivel up any leaves that are affected by GM even if it isn't apparent to the naked eye. I think that is one reason it works on Late Blight if used early enough. The same can be said for its use on GM. If you allow the Gray Mold to progress to far and for too long there is no stopping it as it acts almost like LB at that stage and gets in the fruit and gives the stems lesions. That is one of the reasons I recommend using a copper spray every week to reduce the chance of GM getting out of hand. I tried Daconil as a preventive but found it was not effective for me but the copper really worked well. Usually I have to use the bleach after or during an extended rainy spell when the copper is not effective because it gets washed off.

Bill

[Gardeneer]

Back in PNW, when the rain season starts ( sometimes mid September on ) I used to get GM.
I didn't mind if the plants died because by mid October practically the season would be over. But the worse part was that the fruits were affected, even in still green stage.
in 2015 I tried bleach spray and it helped a lot.
You can start spraying early on , mainly the top of soil / mulch and the lower part of the stems. That is where the spores thrive and come up, me thinks.
Bacteria and fungi thrive in moist and stagnant condition. So pruning lower leaf branches and lightening up further up can help by allowing the air pass thru and keep the foliage dry, as much as possible.

[zipcode]

Originally Posted by gorbelly

Question: do you guys spray your peppers and eggplants with fungicide?

I've had bad years of late blight a long time ago. They wiped the tomatoes completely. Peppers thrived, not one sign. They actually liked the continuously humid weather.
LB needs very wet conditions, so something like covering your tomatoes for a few weeks to keep them from direct rain will help a lot. Also one stem pruning and proper spacing. My aunt never pruned, my plants recovered if infestation wasn't too bad and weather turned good, her's never did.

[SueCT]

Doesn't Daconil protect against Late Blight? If you are worried about conditions being favorable for it, you can start preventative spraying now. It would at least help decrease your losses if it hits near you. I was recently thinking, since LB involves the fruit, is it enough to spray the leaves and stems or do you need to cover each fruit as well? I am already spraying for Early Blight, but I don't usually spray the fruit, although it does get some over-spray just from doing the leaves.