Sigatoka, Fiji
Identification request
Disease-like damage on Tomato

Dear Pestnetters,

Attached are pictures of damage symptoms on Tomato (variety from India) - determiate variety.

Farmer confirms that he had grown this variety a few times already but this is the first time he faced this problem and it seems unfortunate that he may lose most of the harvest. Damage covered whole plot.

The area planted is <1/4 acre with about 1000 plants. Crop was not staked so fruits on the ground - likely a reason why symptom spread so fast. Anyway, the farmer thinks the cause: 1. Started from the fruit calyces; 2. Flood early this year may have brought the disease to his farm;3. He sprayed Yates Liquid Potash at flowering stage and maybe something went wrong - before never spray this and no problem.

Anyway symptoms start on the fruits as tiny dots then becomes brownish spots which then enlarges to clear brown watersunken like lesions whereby many coalesce and others crack but only damaging the skin layer. The fruit flesh seems okay but then quality is lost to appearance so potential loss for farmer with this phase. The farmer has a younger plot next to this old infected plot which he is trying to prevent spread of damage. 

Please if anyone is familiar with this damage and have some ideas/information on the possible I'D or control to share.

Many thanks


Posted on user's behalf




We have received a response from Graham Walker who asked Bob Fullerton and Peter Wright, Plant & Food Research, Auckland, New Zealand for opinions.

This is the message from Graham - "Hi Mani Bula from a cold Auckland. Comments (cut and paste) below from my very experienced colleague at PFR, Peter Wright, who responded to one from Bob Fullerton":

Hi Bob

Like you, I’d say most likely disease is bacterial spot caused by the bacterium Xanthomonas vesicatoria, which attacks green but not red tomatoes.

But in the photos I’d have liked to seen more slightly raised to scabby spots on the fruits rather than the sunken spots/lesions.

Most outbreaks of the disease can be traced back to heavy rainstorms that occurred in the area. Infection of leaves occurs through natural openings. Infection of fruits commonly occur through insect punctures or other mechanical injury.

Prevention & Treatment: Only use certified disease-free seed and plants. Avoid areas that were planted with peppers or tomatoes during the previous year. Avoid overhead watering by using drip or furrow irrigation. Remove all diseased plant material. Prune plants to promote air circulation. Spraying with a copper fungicide will give fairly good control the bacterial disease.

Cheers, Peter Wright
Plant Pathologist
Pukekohe Site Manager

Posted on user's behalf