Wednesday, October 14, 2015

Apple Tree Diseases: Monitored Sprays for Apple Scab

This post is in continuation to my previous post on Apple Diseases:Holistic Management of Apple Scab. Here we are going to discuss about Monitored spray control

There are two spray strategies for controlling the diseases i.e. preventive and curative. Since this disease is a polycyclic, the spray schedule should focus on reduction of inoculum and protective covering before the infection takes place based on the predictive models developed at RHRTS Mashobra.

Monitored Spray control:           
 Among two different monitored spray strategies (curative and eradicative) as developed and tried in the orchards, the curative sprays with well timed application of Ergosterol-biosynthesis-inhibiting (EBI) fungicides even after 72 and 96 hour of the predicted infection periods is not only more effective but also economical for control the disease with three lesser sprays.
Av Temp
Minimum wetness (hr)
Scab appear (days)

The monitored spray programme developed for Indian conditions at Regional Horticultural Research and Training Station, Mashobra, Shimla for the control of spring and summer scab conditions is described below. This strategy is recommended to orchard areas where scab is present.

First Spray:
At green tip stage if scab during last three years was present and temperature after rains remained above 10oC. The spray strategy to control primary scab must include high residue fungicides for better protective action for longer duration. The strong bio-efficacy of dodine, mancozeb, dithianon, and captan is established on apple parts. The residues of these fungicides are persistent, stable and re-distributive on the foliage and remain effective against primary infection up to 36 days. Hence recommended at green tip stage as first spray under monitored control program in Himachal Pradesh.

Second Spray:
Second spray at pink bud stage is recommended to give protective coverage on plant parts to control primary scab infection during the long flowering session. However, according to monitored spray strategy, this spray is considered to be optional and should be given only if first spray is not given or continuous wet conditions prevailed after the first spray. The fungicides recommended at this stage are both protective as well as curative. However, it is also observed that at high altitude locations (above 6500 ft) where primary infection generally initiates after pink bud stage the first spray at green tip stage is inappropriate. Benzimidazole and EBI fungicides having protective/ curative and broad-spectrum mode of action is recommended for such locations at pink bud stage (as first spray) to control invisible infection caused by apple scab, canker fungi, powdery mildew, core rot and leaf blotch. However, the sensitive flowering stage is avoided for any spray as might obstruct the cross-pollination process.
Criteria for sprays:

In addition to its anti-fungal properties it also help in improving fruit set and can be used safely during bloom.

Third Spray:
Third spray at petal fall stage is very essential to protect the newly emerged fruit-lets against primary scab and powdery mildew infections. Moreover, the earlier sprays given either through first spray or at pink bud stage are found ineffective all through the long flowering period of apple. The brands of benzimidazole and EBI are recommended at this stage also having both protective curative and anti-sporulant actions. This group of fungicides is effective to other summer diseases as well and also acts as anti-senescent and increased fruit set.

Fruit Development Spray:

At fruit development stage the actual monitored spray strategy implies where curative fungicide sprays are recommended after the infection period instead of routine sprays. There are three options of sprays and type of fungicides use according to the prevailing weather and scab conditions in the orchards.

Most effective option of curative (EBI) fungicides is to kill the fungus in host tissues after the infection has occurred. However, the fruit development sprays can be extended for longer duration or discontinue in case there is no visible scab on leaves and fruits out of primary infection. This can also be ascertained by the overall scab records in the last three years and no primary symptoms have appeared till date in the current period.

Dormant spray:

Dormant sprays of 5 per cent urea a foliar nitrogenous fertilizer at leaves shedding stage and followed by a spray of Bordeaux mixture (1%) are most effective IDM strategy used to eradicate the most overwintering pathogen/diseases on apples.

In coming posts I shall be discussing about the cankers.

Thursday, October 8, 2015

Apple Tree Diseases: Holistic Management of Apple Scab

Reduction of Primary Inoculum:

The primary inoculum of the disease resides in the infected leaves fallen on the orchard floor. These lesions develop into pseudothecia that further develop ascospores that got released in coming spring season and cause primary infection. To reduce the primary infection primary inoculums should be reduced. Thus phytosanitation plays an important role in reducing the primary inoculum. During Oct Nov when 80 per cent leaves have fallen the leaves either should be collected with the help of rake or should be sprayed with 5 percent urea solution. The spray should be directed on orchard floor rather than on the trees. As the nitrogen concentration of 5 percent is required to decompose the fallen leaves that is containing the scab infection and harbouring the fungus for the development of pseudothecia. Since it will decompose faster than the pseudothecia development thereby reducing the primary inoculum of the disease.

Modification of environment:
The disease development requires leaf wetness. The wetness is always affected by relative humidity. Means more the relative humidity slower will be the drying time thus increasing the leaf wetness period. Longer will be the leaf wetness period more severe disease will appear in the orchard. This situation warrants for better sun penetration and air circulation. If we avoid dense canopy and follow proper training and pruning practices we can improve the air circulation and light penetration thereby reducing the chances of scab to appear in the orchard.
Monitored spray control:
             There are two different strategies (curative and eradicative) for monitored sprays, the curative sprays with well timed application of Ergosterol-biosynthesis-inhibiting (EBI) fungicides even after 72 and 96 hour of the predicted infection periods is not only more effective but also economical for control the disease with three lesser sprays.

In coming posts we shall be discussing about the monitored sprays....

Wednesday, October 7, 2015

Apple Tree Diseases: Holistic Management of foliar diseases

बीमारियों के प्रबन्धन के लिये हमें डिज़िज़ ट्राईएंगल को समझना आवश्यक है, यही बीमारियों के एकीकृत प्रबन्धन का आधार है। बीमारी त्रिकोण के तीन घटकों (कारक, होस्ट, वातावरण) में होस्ट को तो बदला नहीं जा सकता है परन्तु कारक एवं वातावरण में वांछित बदलाव कर के बीमारियों का ईको फ़्रैंडली प्रबन्धन किया जा सकता है। एकीकृत प्रबन्धन की कड़ी का पहला सिद्धांत फ़ाईटो सैनीटेशन है जिसके द्वारा हम बीमारी के कारकों का प्राईमरी ईनोकुलम कम करते हैं ये अधिकतर सर्दियों में किये गये वो कार्य होते हैं जिनके द्वारा हम बीमारी से ग्रसित पत्तों व पेड़ के अन्य भागों को साफ़ करते हैं। दूसरा सिद्धांत बीमारी के लिए फेवरेवल वातावरण को मोडिफाई करने से भी बीमारियों का प्रबन्धन किया जा सकता है। उदाहरण के लिये मार्सोनिना के लिये उच्च तापमान के साथ-साथ उच्च आर्द्रता भी चाहिए। ऐसी स्थिती में क्या किया जाए? सर्दियों में कैनोपी मैनेज़मैंट द्वारा धूप व हवा का सर्कुलेशन इम्प्रूव कर पेड़ों का माईक्रोक्लाईमेट बदला जा सकता है। जिसमें आजकल घास की सफ़ाई व समर प्रूनिंग भी शामिल है। घास की सफाई व समर प्रूनिंग से क्या होगा? हवा का सर्कुलेशन इम्प्रूव होगा तथा हाई रिलेटिव ह्युमिडिटी की स्थिती भी उत्पन्न नहीं होगी जिससे पत्तों में आने वाली बिमारियों के लिये वांछित वातावरण में बदलाव होगा और बीमारी उत्पन्न नहीं होगी। वातावरण से ही सम्बंधित बायोकंट्रोल एजेंट्स का प्रयोग तीसरे सिद्धांत के रूप में कार्य करता है। कैसे? फाइलोप्लेन में बहुत सारे माईक्रो-ओर्गेनिज्मज होते हैं जो बीमारी के कारकों को बीमारी फैलाने नहीं देते हैं। यदि वातावरण बीमारियों के लिये फ़ेवरेवल हो रहा हो तो हमें पहले ही कुछ बायोकंट्रोल एजेंटों जैसे स्यूडोमोनास, बैसिलस इत्यादि का प्रयोग करना चाहिये। हालांकि यूनिवर्सिटी की रिसर्च में इनके एनकरेजिंग रिजल्ट मिले हैं फिर भी अभी इनमें और शोध की आवश्यकता है ताकि ये सब रिकोमेंडेशन में आ सके। यदि हम इन सब सिद्धांतों का प्रयोग करें तो चौथे सिद्धांत यानि पेस्टीसाईड्ज़ की आवश्यकता बहुत कम हो जाती है। इससे न केवल फल उत्पादन की लागत कम होती है अपितु उच्च गुणवत्तायुक्त फल मंडियों में पंहुचा कर उच्च दामों पर बेचा जा सकता है। जिससे न केवल लाभ बढ़ता है परन्तु उपभोक्ता की सेहत भी बनी रहती है।