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Strawberry Plasticulture - September 14, 2002 (Saturday,
2:00 pm) -1. General update: a) Western and Central Piedmont Ares of NC west of Raleigh remain critically dry! Record low ponds, wells and streams have made planting plugs a necessity this fall. In regions where planting starts in the 3rd week of Sep, growers have started to re-wet the plasticulture beds in anticipation of planting, and we are hearing of problems with high algae levels in ponds clogging drip systems! b) Tropical Depression Hanna is expected to spread "copious" amounts of moisture into the Carolinas today (monsoon type rains began in N. Raleigh at 10 am). It would appear that theses showers and thunderstorms will reach as far west as Asheville. Sunday will have morning rains and then p.m. showers and thunderstorms with some sun on Monday (Sep 16). We expect at Clayton to get .42 in today (Sat) and another .66 in on Sun and finally .45 in on Monday!
c) The rainfall accumulation of 1.5 inches at Clayton Central Crops from Hanna will further delay our fumigation. We keep running into snags of various kinds! Our soil was actually looking fairly dry on top yesterday (Sep. 13), but beneath we still had good moisture from Aug 25 to Sep 1 rains (Figure 2).
Figure 2. Sandy loam soil at Clayton that was pre-bedded (Sept 10) and appeared to be a little dry on top (Sep 12), but was NOT. The tractor actually had some problems on Tuesday with a pretty moist soil underneath from a week-long rain, Aug 25-Sep 1. Plans for fumigation on Monday (Sep 16) have now been scrapped by Hanna! Not sure when we'll finally be able to get it done? Any fumigant with plant-back of more than 14 days is definitely going to be difficult to use now - we will miss our target planting date by more than 1-week with an Alternative to MeBr that requires 3 weeks of waiting period before planting. Our beds are about 32 inch on top after pre-bedding.
From last September 27, 2001, Frank made these comments in an advisory: "Over the last 3 days we have diagnosed anthracnose in several strawberry plug-production facilities. The problem does not appear to be restricted to one or a few operations but may be more widespread. To date, we have characterized what appears to be the Colletotrichum acutatum strain. This strain is typically associated with the anthracnose fruit rot and less commonly with plant collapse. In a plug production facility, the problem appears to start has hot spots. Plants in such hot spots show a general unthriftiness, remain stunted and are slightly discolored compared to neighboring symptomless plants. Such plants may resemble symptoms due to lack of water or high salts injury (Fig. 3). As the disease progresses, one or more leaves wilt and the base of the leaf (petiole) becomes brown and wet (Fig. 4). Advanced stages of the disease result in plant collapse. Botrytis crown rot and Pythium or Rhizoctonia crown rot may have similar symptoms. Therefore, it is essential diseased plants be properly diagnosed. For the diagnostician, incubate infected tissue for 24 hrs and observe for characteristic spores and fungal structures such as sterile setae. In some cases, we have isolated the pathogen. If a grower has such a hotspot in the greenhouse, contact your local
Cooperative Extension Agent and send samples to the Plant Disease and
Insect Clinic according to the clinic instructions (http://www.ces.ncsu.edu/depts/ent/clinic/Submit/submit.htm).
Once it arrives there, I will diagnose the samples (do not send samples
directly to me). "
Fig. 3. Plug plants exhibiting what may appear to be salt injury, but these Chandler plug plants were positively diagnosed to be infected with anthracnose.
Figure 4. As the disease (anthracnose) progresses, one or more leaves wilt and the base of the leaf (petiole) becomes brown and wet . Advanced stages of the disease result in plant collapse, as this has occurred in the third plug cell (from right to left) in the foreground. Frank continued in the advisory of last September (27): "If an alternative source of plants is not a realistic option (or, in the case of Sep 2002, water resources don't exist for fresh dugs), immediately remove all infected trays and 1-2 sets of trays surrounding the infected area(s). Cull hard. Do not handle plants when wet and avoid touching healthy plants after handling suspected diseased plants. Minimize overhead watering. " Call this morning from Sandhills producer: Fortunately, I had my cell phone on this morning, and spoke with a grower in the Sandhills who learned last evening from Frank that he definitely has anthracnose in his plugs. After immediately removing all infected trays and 1-2 sets of the trays surrounding the infected areas, he is planning to use a tank mix of captan ( 2 lbs per acre of active ingredient; e.g. 4lbs Captan 50WP per acre) with Quadris (12.4 fl oz per acre). This producer has a plug propagation area that occupies a 0.2 acre area (1/5th Acre), and thus he would need to apply to this production area:
If you have any further questions or concerns, please contact Dr. Frank
Louws E. Barclay Poling, Small Fruit Specialist |
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