Mites and feeding signs on lower leaf surface. Aphids also present.

Two-spotted spider mite (TSSM) infestations have recently been discovered in high tunnels.

TSSM feeding results in small white pin-spots on the upper leaf surface (see photos).  Mites are actually underneath leaves.  These pests can increase dramatically in the warm, dry environment of the tunnel.

Check 5 plants each in 5 separate locations in the tunnel.  Inspect the entire plant, and be sure to check the underside of leaves that display the whitish mite feeding.  If mites are found, it is best to immediately treat.  TSSM is much more easily managed, when the problem is addressed at low levels.  If allowed to spread throughout the tunnel, TSSM will be much more difficult to control.

See the 2016 Commercial Vegetable Production Recommendations – Pest Management section for materials that are labeled for use in greenhouse structures, including those that are OMRI approved.
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Syngenta Crop Protection released Orondis, a new fungicide with a new mode-of-action for use in vegetable production this past winter. Because of its winter registration, Orondis was not included the 2016 Mid-Atlantic Commercial Vegetable Production Guide.

Orondis (oxathiapiproplin, U15) targets the oxysterol binding protein that is a part of the fungal cell wall. The active ingredient inhibits growth of the fungus as well as sporangia production and zoospore germination. Orondis has a low solubility (i.e., locally systemic), is translaminar; and will protect new growth.

Orondis is currently sold as a co-pack with either mefenoxam (Orondis Gold), chlorothalonil (Orondis Opti), or mandipropamid (Orondis Ultra). Growers will be required to tank mix Orondis with its partner during 2016 season. In 2017, the partners will be formulated together. Importantly, Orondis will not receive an individual label in the US.

Orondis has different use rates and restricted seasonal use. The labels need to be followed carefully and accordingly to help manage fungicide resistance development. Simply, if Orondis is applied via drip system, it cannot be used as a foliar spray (and visa-versa). If Orondis is applied as a foliar application it cannot be used via the drip. Thus, growers planning on using Orondis need to plan ahead of time and accordingly! The rates for Orondis and it counterpart will differ by crop, pathogen, and desired use (drip vs. foliar). [Read more…]

Unfortunately, closed greenhouses retain heat and humidity which can spell problems if left unchecked.

Remember, high relative humidity equals wet leaves which favor the development of fungal diseases such as Botrytis or bacterial diseases such as bacterial leaf spot. To avoid potential problems, do your best to vent out as much humidity as possible in the late afternoon and/or early morning. Turn on circular fans to promote air movement and finish watering earlier enough in the day so leaves have enough time to dry out before nightfall.

As a side note, stressed transplants where water and/or fertility have been withheld are also more prone to disease development. A light fertilizer application may go a long way in improving transplant health before setting in the field.

Please see Table E-14 and pages E52-E54 of the 2016-2017 Commercial Vegetable Recommendations Guide for a list of control options.