Preventing Late Blight, etc. on Tomatoes and other Nightshades – by JOANNE RICE (2)

You have my permission to use this information in any way that you see fit.

Below is the write up that I made for our Board of Directors.  I have included a lot of questions and answers that Dr. Michael Coffey, plant pathologist and Dr. Thomas Perring, entomologist exchanged with me.  The list of host plants is at the end.  Dr. Coffey states that all solanaceous plants are host plants and should be eliminated for a period of two months each year. Also, do not ever grow volunteer tomatoes.  As soon as they emerge from the ground, pull them up and discard them.

It is interesting to note, that the mite and blight have the same hosts, that is why I am lumping them together.  We had to do a very difficult clean up and it is important that gardeners pay attention to keeping their gardens weed free, host plants out and keep all leaves that do not look perfect on a tomato plant, cut off.  If left, of course, the spores blow on to other leaves and then you are off and running with a big problem.  Never compost any of the night shade plants–potatoes, tomatoes, egg plant, peppers, tobacco.  Composting may not kill the spore.  In fact, I never compost anything that has any insects or disease, just in case.

One other thing I would like to pass along.  One spraying with sulfur does not do it.  Ortho has a wettable sulfur sold in most nurseries and two tablespoons per gallon of water sprayed on tomato plants every two weeks preventably will handle mildew, mite and possibly blight.  Best way to handle blight is the clean up, clean gardens, no potatoes of any kind, including sweet potatoes and a very watchful eye.   Once we started using the wettable sulfur, our tomato plants were simply awesome.  I had some plants start to go down early on and thought I would lose them and the minute that I used the wettable sulfur, they came back and were simply beautiful.

It is good to note that most of the commercial tomato growers in California dust with sulfur beginning in early M ay. Theydoitforthemite.BR Dusting is not an option for us because if you inhale sulfur, it becomes sulfuric acid in your lungs and burns your lungs.

Yes, Daconil can be used for blight.  Best to be used early to prevent.  Treating after infection is more difficult.  Soap Shield from Garden’s Alive is also an option.

After so many years of struggling with blight and mite, I am so heartened that these two specialists from UC Riverside have shown us the right path to healthy tomatoes.  We are now in our first month of no host plants and have one month to go and then will allow tomatoes, egg plants and peppers to be planted again.  We demand that all gardens and pathways be weed free. 

I hope that this will help some garden people to have a better handle on tomato diseases.  Until last year, we were struggling.  Now we are not.

Here is the website for our gardens.
   www.lbcga.org

Most sincerely,
Joanne Rice

See below:

THE FOLLOWING INFORMATION HAS BEEN SENT TO ME BY DR. MICHAEL COFFEY, PLANT PATHOLOGIST AT UC RIVERSIDE WHO IS GOING TO HELP US MANAGE OUR TOMATO BLIGHT PROBLEM  AND BY DR. THOMAS PERRING OF UC RIVERSIDE WHO IS A TOMATO RUSSET MITE (TMR) SPECIALIST.  THEY HAVE REALLY BEEN VERY SUPPORTIVE AND WHEN E MAILED,  REPLY WITHIN MINUTES.

WHEN ASKED WHAT WE SHOULD DO ABOUT THE BLIGHT AT THIS TIME OF YEAR,  DR. COFFEY SAID THIS.

“REMOVE AND DISCARD EVERY VOLUNTEER TOMATO PLANT.
REMOVE AND DISCARD EVERY VOLUNTEER POTATO PLANT.
LATE BLIGHT IS NOT A SOIL BORNE DISEASE SO TREATING THE
SOIL WOULD BE OF NO CONSEQUENCE.
REMOVE ALL SOLNACEOUS PLANTS AND WEEDS, ESPECIALLY
HAIRY NIGHTSHADE.
YOU WILL HAVE TO HAVE THE COOPERATION OF THE ENTIRE
MEMBERSHIP
AS THE TOMATO SEASON APPROACHES,  I WILL INSTRUCT YOU
FURTHER.”

DR. COFFEY SAID TO CONVEY TO THIS BOARD THAT “YOU HAVE
A PLANT PATHOLOGIST NAMED MICHAEL COFFEY WHO IS
WILLING TO HELP YOU.”

DR. COFFEY LATER WROTE THIS:  ”  REGARDING LATE BLIGHT OF TOMATOES,  I AM IN THE PROCESS OF WRITING A REVIEW ARTICLE FOR PLANT DISEASES ON THIS TOPIC.  I WILL SHARE MY THOUGHTS, FINDINGS AND EXPERIENCE WITH YOUR GARDEN COMMUNITY PRIOR TO THE NEXT TOMATO GROWING SEASON.  I WOULD ALSO LIKE TO DONATE ABOUT 200 TOMATO PLANTS OF DIFFERENT VARIETIES AT THIS STAGE.

LATE BLIGHT DOES NOT SURVIVE IN THE SOIL.  IT DOES HOWEVER, OVERWINTER ON VOLUNTEER PLANTS, POTATO AND TOMATO AND ON CERTAIN SOLANACEOUS WEEDS, NOTABLE HAIRY NIGHTSHADE.  THE DESTRUCTION OF VOLUNTEERS AND HAIRY NIGHTSHADE IS HIGHLY DESIRABLE.

LATE BLIGHT CAN ALSO BE INTRODUCED ON YOUNG TOMATO SEEDLINGS/TRANSPLANTS BOUGHT AT THE NURSERY SUPPLIER.  THIS IS A QUITE COMMON METHOD OF INTRODUCTION AND SPREAD.  YOUNG PLANTS NEED TO BE INSPECTED CAREFULLY ONCE THEY ARE PLANTED AND ANY SHOWING SYMPTOMS, DESTROYED AND SURROUNDING PLANTS TREATED IMMEDIATELY.”

DR. COFFEY DID NOT MENTION EGG PLANT OR PEPPERS IN REGARD TO LATE BLIGHT BUT I READ THAT PEPPERS AND EGGPLANT ARE IMMUNE TO THE DISEASE BUT CAN HARBOR THE SPORES OVER THE WINTER. 

WHEN I ASKED MANY QUESTIONS REGARDING THE TOMATO RUSSET MITE,  DR. THOMAS PERRING HAD THIS TO SAY.

QUESTION: AFTER THE RUSSET MITE FINISHES DEVASTATING THE LEAVES OF A TOMATO PLANT,  WHERE DOES IT GO?
ANSWER:  MOST OF THEM DIE.  THE ONES THAT MAKE IT TO ANOTHER SOLANACEOUS HOST WILL CONTINUE LIVING, PRODUCE EGGS, ETC.  THE POPULATION GROWTH SLOWS CONSIDERABLY IN THE WINTER BUT IS STILL PRESENT.

QUESTION:  LITERATURE SAYS THE MITE OVER WINTERS ON CERTAIN PLANTS.  I WOULD LIKE TO KNOW THE LIFE CYCLE OF THE MITE.
ANSWER:  IF YOU SEND ME YOUR ADDRESS,  I WILL FORWARD SOME LITERATURE ABOUT THIS MITE. (HE DID AND I AM INCLUDING THE IMPORTANT PARTS IN THIS DOCUMENT).

QUESTION:  I UNDERSTAND THAT MAY AND JUNE ARE THE BEST MONTHS TO DUST/SPRAY THE TOMATO PLANTS FOR THIS MITE.
WHY?
ANSWER:  THIS IS THE TIME BEFORE THE POPULATION LEVEL REACHES SUCH HIGH NUMBERS, SO YOU DON’T HAVE TO KILL SO MANY INDIVIDUALS.  ALSO, IT IS THE TIME OF YEAR THAT THE TEMPERATURE IS STARTING TO GET WARM, A CONDITION THAT DRIVES MITE DEVELOPMENT.

QUESTION: ANY COMMENTS ON SULFUR DUST VERSUS WETTABLE SULFUR?
ANSWER:  DUSTING SULFUR WOULD BE PREFERRED BECAUSE YOU GET BETTER COVERAGE WHERE THE MITES LIVE, BUT WETTABLE  SHOULD ALSO DO THE TRICK.

QUESTION:  ARE WE ON THE RIGHT TRACK FOR CONTROL OF THIS MITE?
ANSWER:  YES, TRY TO REDUCE THE OVERWINTERING SOLANCEOUS PLANTS AND DUSTING WITH SULFUR IN MAY AND JUNE SHOULD DO IT.

QUESTION: 10/08/03   I AM WONDERING IF THERE IS ANYTHING THAT WE SHOULD BE DOING AT THE PRESENT TIME THAT WOULD HELP CUT DOWN ON THE RUSSET MITE POPULATION?  I NEED A PLAN OF ATTACK.
ANSWER: “AN AGGRESSIVE WEED CLEAN UP WILL GO A LONG WAY TO REDUCE MITE HOST PLANTS.  IF YOU SIMPLY HAD A STRATEGY FOR GARDENERS TO REMOVE PLANT MATERIAL IMMEDIATELY FOLLOWING THEIR LAST HARVEST, THIS WOULD HELP A LOT.  TYPICAL GARDENERS WILL HARVEST UNTIL THE VERY LAST FRUIT IS TAKEN FROM THE PLANT, EVEN IF THE PRODUCTION IS PRETTY MUCH OVER.  THE MITE IS ALSO ON TO THE NEXT CROP, AND ABANDON THE OLD PLANTS.  THIS ALLOWS THE OLD PLANT TO BECOME A BUG FACTORY.  IF YOU HAD A RULE FOR REMOVING USED-UP PLANTS, IT WOULD REDUCE SOME OF THESE PROBLEMS.

IF YOU HAVE A ‘HOST FREE PERIOD’ BEFORE TOMATO PLANTING, TOMATO RUSSET MITE WILL BE ELIMINATED FROM THE GARDENS.  THE SOURCE OF INFESTATION THUS WOULD COME FROM OUTSIDE AND BE SIGNIFICANTLY LESS THAN FROM INSIDE THE GARDEN.”

WE NEED TO IMPLEMENT THE THINGS THAT DR. COFFEY AND DR. PERRING HAVE SUGGESTED THAT WE DO TO GET OUR GARDEN ENVIRONMENT BACK TO NORMAL.

KEVIN HOLMAN IS PRICING THE COST OF SPRAYING OF ALL TOMATO PLANTS IN MAY AND JUNE AND IT MUST BE MANDATORY OTHERWISE ALL OF THE ABOVE IS FOLLY.

IF WE DO NOT TAKE CARE OF THIS PROBLEM,  WE WILL NOT BE GROWING TOMATOES AS IT WILL BECOME AN EVEN BIGGER PROBLEM WITH EACH ENSUING YEAR,  IF THAT IS POSSIBLE.

CLEAN UP SHOULD BEGIN IMMEDIATELY AND ALL TOMATO VOLUNTEERS, POTATO VOLUNTEERS,  TOMATO PLANTS, PEPPER PLANTS, EGG PLANT, POTATO PLANTS,  PETUNIAS, NICOTINIA AND OTHER THINGS LISTED BY DRS. COFFEY AND PERRING PULLED OUT BY NOVEMBER 30, 2003.   ALL GARDENS SHOULD BE WEED FREE, ESPECIALLY THE MORNING GLORY (FIELD BIND WEED).  A BIG JOB BUT HAS TO BE DONE AS PART OF THE CLEAN UP.  THIS SHOULD BE COMPLETED BY NOVEMBER 30 2003.  WE SHOULD ASK FOR EIGHT VOLUNTEERS TO MONITOR THE CLEAN UP.

HERE IS THE LIST OF HOST PLANTS THAT HARBOR THE MITE and BLIGHT.

TOMATO  (LYCOPERSICON ESCULENTUM)
HAIRY NIGHTSHADE  (SOLANUM VILLOSUM)
MORNING GLORY  (CONVOLVULUS SP.)
POTATO  (SOLANUM TUBEROSUM)
BLACK NIGHTSHADE(SOLANUM NIGRUM)  Being grown by our Oriental
Members.
JIMSON WEED  (DATURA STRAMONIUM)
CHINESE THORN APPLE  (DATURA FEROX)
CAPE GOOSEBERRY  (PHYSALIS PERUCIANA)
WILD BLACK CURRANT
PETUNIA  (PETUNIA HYBRIDA)
TOMATILLO  (PHYSALIS IXOCARPA)
POPOLO  (SOLANUM NODIFOLIUM
NIGHTSHADE  (SOLANUM DOUGLASII)
SMALL FLOWERED NIGHT SHADE  (SOLANUM NODIFLORUM)
WILD GOOSEBERRY  (PHYSALIS MINIMA)
TOBACCO  (TOBACCO NICOTIANA SP)
AMETHYST  (BROWALLIA AMERICANA)
BELL PEPPER  (CAPSICUM ANNUM)
CHERRY PEPPER  (CAPSICUM ANNUM)
TOLGUACHA  (DATURA METELOIDES)
LYCOPERSICON CHEESMANII
LYCOPERSICON CHILENSE
LYCOPERSICON  GLANDULOSUM
LYCOPERSICON  HIRSUTUM
LYCOPERSICON  PERUVIANUM
LYCOPERSICON PIMPINELLIFOLIUM
WHITE HORSE NETTLE  (SOLANUM ELEAGNIFOLIUM)
SOLANUM LACINIATUM
EGGPLANT  (SOLANUM MELONGENA)
JERUSALEM CHERRY  (SOLANUM PSEUDO-CAPSICUM)
FIELD BINDWEED  (CONVULVULUS ARVENSIS)  (OUR MORNING GLORY)
BRINJAL

RESPECTFULLY SUBMITTED
JOANNE RICE
FIRST VICE PRESIDENT
LBCGA
10/14/03