`The Cost of Anthracnose

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The Cost of Anthracnose

Mar. 5, 2012
Julie Butler

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Photo: olivediseases.com

Calls are being made for a more con­certed effort to com­bat the dev­as­tat­ing olive dis­ease anthrac­nose, which last sea­son caused about €53 mil­lion ($71m) dam­age to the olive oil sec­tor in Italy’s Puglia region alone.

The fun­gal dis­ease has also been reported in Por­tu­gal, Spain, Greece, Tunisia, Ser­bia, Mon­tene­gro, Aus­tralia, New Zealand, South Africa, Brazil, Argentina and Uruguay, and the main treat­ment — cop­per-based fungi­cide — is not always effec­tive in sup­press­ing it.

Ital­ian Mem­ber of the Euro­pean Par­lia­ment Ser­gio Sil­vestris, who is from Apu­lia (Puglia), and Aus­tralian Vera Sergeeva, who spe­cialises in olive pests and dis­eases, are among those seek­ing a stronger response.

Sil­vestris recently asked in a writ­ten ques­tion if the Euro­pean Par­lia­ment would allo­cate fund­ing to mon­i­tor the spread of the epi­demic and for pre­ven­tive mea­sures.”

The dis­ease is caused by a fun­gus, and symp­toms tend to appear mainly in fruits when they have nearly ripened, pos­ing a seri­ous prob­lem as regards pro­duc­tion. Dis­eased olives drop pre­ma­turely from the trees, result­ing in yield loss; when pressed they pro­duce a very tur­bid and highly acidic red­dish oil of poor qual­ity,” he said.

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In its reply, the EC said that because the organ­isms caus­ing olive anthrac­nose — Col­letotrichum gloeospo­ri­oides and C. acu­ta­tum — are widely dis­trib­uted in the EU, they are not eli­gi­ble for reg­u­la­tion or a finan­cial con­tri­bu­tion under the EU plant health regime. And given other press­ing pri­or­i­ties and lim­ited funds, the EC did not envis­age allo­cat­ing spe­cific research fund­ing for mon­i­tor­ing or pre­vent­ing the dis­ease, it said.

Sergeeva told Olive Oil Times that there was a need for an inter­na­tional group of highly-qual­i­fied sci­en­tists, indus­try spe­cial­ists and olive grow­ers to com­bine efforts on anthrac­nose man­age­ment. Coor­di­na­tion of field tri­als would help pre­vent research dupli­ca­tion in dif­fer­ent coun­tries and make the research more pro­duc­tive. We have to share our knowl­edge and work together,” she said.

What is anthrac­nose and how wide­spread is it?

It’s best known for infect­ing man­goes, but grape, avo­cado, lemon, orange, almond, straw­berry, apple and papaya are among other crops anthrac­nose affects. Australia’s pis­ta­chio farm­ers, for instance, expected a bumper last year but instead, after sum­mer down­pours saw the pest thrive, they had a har­vest from hell, with their nuts black­ened by the fun­gal dis­ease.

Sergeeva says that anthrac­nose is a wide­spread and severe dis­ease in most olive-grow­ing coun­tries, caus­ing sig­nif­i­cant yield losses, poor fruit and olive oil qual­ity. In Spain, the over­all loss in net income for the olive indus­try caused by Col­letotrichum fungi is esti­mated to be over $93.4 mil­lion a year,” she said.

In Aus­tralia, the dis­ease affects up to 80 per­cent of olives in sus­cep­ti­ble cul­ti­vars such as Barnea, Man­zanillo, Kala­mata and UC13A6. In Por­tu­gal, it is very com­mon and has caused losses of up to 100%, par­tic­u­larly in the widely cul­ti­vated vari­ety Galega, which is very sus­cep­ti­ble.”

In autumn 2006, sig­nif­i­cant losses were reported from cul­ti­vars such as Arbe­quina and Picual, pre­vi­ously regarded as mod­er­ately resis­tant, and widely cul­ti­vated through­out the Iber­ian penin­sula,” Sergeeva said.

Sergeeva explained what’s known, and what’s yet to be under­stood, about anthrac­nose.

What would be most use­ful for pro­duc­ers to know about this dis­ease?

Dr. Vera Sergeeva

Dr. Sergeeva: That the infec­tion can per­sist from sea­son to sea­son and that its inci­dence depends on fac­tors includ­ing olive vari­ety, envi­ron­ment and the vir­u­lence of the pathogen. Warm, rainy, misty and humid con­di­tions or heavy dews have been observed to be asso­ci­ated with severe anthrac­nose epi­demics. Over-water­ing should be avoided in the grove where anthrac­nose is present. The objec­tive is to pre­vent dis­ease out­breaks and the devel­op­ment of severe early-sea­son epi­demics.

An olive vari­ety of Ital­ian, Span­ish, Greek or Israeli ori­gin will not nec­es­sar­ily behave in the same man­ner in respect to qual­ity or quan­tity if grown some­where else in the world. In Aus­tralia, for instance, we can grow olives out­side a typ­i­cal Mediter­ranean cli­mate — but with risks.

Is fungi­cide treat­ment expen­sive or com­pli­cated?

Cop­per-based fungi­cides are now the main method of dis­ease con­trol but they are not effec­tive in sup­press­ing anthrac­nose dis­ease in olives under high dis­ease pres­sure.

Dis­ease man­age­ment is also made more dif­fi­cult by the pres­ence of dif­fer­ent species of Col­letotrichum (C. acu­ta­tum and C. gloeospo­ri­oides) and recently a third species in Italy (C. clava­tum). Affected groves may have one or both species of the pathogen present.

Com­plete cov­er­age of large, tall trees is hard to achieve; spray­ing is not very effi­cient and might not be jus­ti­fied or fea­si­ble. While con­trol might occur in some sit­u­a­tions, anthrac­nose can return annu­ally and war­rant a con­tin­ued treat­ment. And in rainy years, the appli­ca­tion of chem­i­cal treat­ments can be dif­fi­cult.

Many olive grow­ers com­plain that stro­bil­urin fungi­cides are very expen­sive. Not every olive grower can afford expen­sive chem­i­cals. And using Amis­tar is com­pli­cated for olive grow­ers because this fungi­cide is phy­to­toxic to cer­tain apple vari­eties. There­fore, as a pre­cau­tion, Amis­tar should not be applied when there is a risk of spray drift onto neigh­bor­ing apple crops.

Resis­tance to the stro­bil­urin fungi­cides in anthrac­nose pop­u­la­tions has been reported on some crops.

Is prun­ing effec­tive in anthrac­nose dis­ease man­age­ment?

Yes, it can be. Dis­eased twigs, pedun­cles, pedicels and suck­ers should be pruned dur­ing the dor­mant sea­son and removed from the grove and destroyed. Prun­ing is also impor­tant to max­i­mize sun­light infil­tra­tion and air move­ment within the tree. This helps with the nat­ural con­trol of anthrac­nose and reduces the pres­sure on the fungi­cide. The idea is to try to pre­vent the life cycle from start­ing or to inter­rupt it once started.

The pre-flow­er­ing (buds) and flow­er­ing (flow­ers) stages are more crit­i­cal for infec­tion; how­ever infec­tion also occurs dur­ing fruit set. In this case, spray­ing would be effec­tive in reduc­ing anthrac­nose. Use two sprays, one before flow­er­ing and one in early fruit set.

What are the pri­or­i­ties for research on anthrac­nose?

The cur­rent prac­tice of apply­ing fungi­cides to con­trol anthrac­nose dis­ease has not been suc­cess­ful. This appears to be due to inef­fi­cient tim­ing of appli­ca­tion and the wrong choices of fungi­cide. While organic olive farm­ers have vir­tu­ally no choice in the selec­tion of fungi­cides, apart from a few types of cop­per, non-organic farm­ers have fol­lowed an irra­tional approach to fungi­cides. There­fore, one of the key objec­tives of dis­ease man­age­ment is to develop a ratio­nal approach to dis­ease con­trol. Dif­fer­ent tim­ings of the appli­ca­tion of the pes­ti­cides and nutri­ents need to be tested to mea­sure con­se­quent dis­ease inci­dence.

Foliar appli­ca­tion of nutri­ents between fruit set and har­vest is a rel­a­tively new con­trol strat­egy and needs more research. Other issues need­ing fur­ther study include the impact of soil amend­ments with nutri­ents or com­post on the devel­op­ment of fun­gal dis­ease and the inter­ac­tion between irri­ga­tion and the dis­ease.

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