Bacterial speck, spot, and canker continue to be perennial problems in Eastern NY. We are learning that effective management is a season-long effort, starting with proper greenhouse sanitation and continuing with regular plant protection. The good news is that there are more tools available for disease management than once thought; the bad news is management is more intensive than we'd like.

Source: Dr. Christine Smart

Source: Dr. Christine Smart

Start with clean stakes

This is a best practice because of other tomato diseases too, so hopefully you are already cleaning your tomato stakes. Every year wooden and metal stakes should be power-washed to remove excess soil, then sterilized using either bleach, Green-Shield,  Xero-Tol, or an equivalent product. It is important for the stakes to sit in a sterilizing solution long enough to penetrate the nooks and crannies of the wood and kill any lurking bacteria or fungal structures. Remember that bleach will damage metal stakes if not rinsed off.

Protect plants starting early

Bacterial diseases are most effectively controlled by preventing their infection. It's not always clear where inoculum comes from, but we know that growers who have struggled with bacterial diseases in the past are having some success with starting a protective spray program shortly after transplanting. The traditional spray for both organic and conventional growers has been copper; however, there is concern about applying the amount of copper per season that would be needed to provide continuous control. Dr. Christine Smart has been doing trialing of alternatives to copper for bacterial canker and bacterial speck, and has found that there are products equally effective to copper available on the market.

                   2017 Bacterial Speck Trial Results: Dr. Smart

    *Products with the same letter are not significantly different

Treatment and Rate/A

Active Ingredient

   Mean AUDPC

(disease over time)

Unsprayed control

234.8 a

Regalia EC 4 qt

Reynoutria sachalinensis extract

174.5  b

Double Nickel LC 32 fl oz

Bacillus amyloliquefaciens

166.3 b

Actinovate AG 12 oz

Streptomyces lydicus

 161.3 b

LifeGard WG 4.5oz/100 gal

Bacillus mycoides

153.8 b

Actinovate AG+Regalia EC

150.0 b

Champ 30 WG  2.0 lb

Copper hydroxide

145.0 b

              2017 Bacterial Canker Trial: Dr. Smart

                           # of fruit without lesions

*Products with different letters are significantly different

It's important to protect leaves because fruit quality will decrease as the plant weakens and is defoliated. However, fruit quality is downgraded by just one lesion. According to Dr. Smart, bacterial infection of fruit occurs before it reaches ping-pong size. Keeping fruit protected prior to this point will effectively result in lesion-free fruit. This knowledge may adjust timing of sprays.

Because copper and other products such as Actigard have, on average across bacterial diseases, equal efficacy, alternating between them could help with resistance management and will reduce copper loading the in soil. All of these products wash off in rains, so protecting weekly or between rain events is recommended for best results with field tomatoes.

One quick note—you will notice that none of the products listed are antibiotics. There are no antibiotics listed for vegetable production—products listed are either broad spectrum biocides, such as copper, stimulate plant immunity, such as Regalia and LifeGard, or competitively colonize the leaf and suppress other bacteria, such as the Bacillus products.