SC Fruit and Vegetable Field Report – November 21, 2022

Spider mites in their red-colored winter form

Spider mites in their red-colored winter form.
Justin Ballew, ©2022, Clemson Extension

The effect of row covers on spider mite pest problems is not entirely clear. Studies in NC found that row covers did not influence spider mites during cold winters and when transplants were NOT infested with spider mites initially. Mite-infested transplants will likely fare worse. During warmer weather, extended row cover use appeared to exacerbate spider mite problems. Lastly, if you plan on buying and releasing predatory mites, you must release them when spider mite populations are still low and also avoid using broad-spectrum insecticides (e.g., pyrethroids). Some acaricides are also safer than others (e.g., Acramite and Nealta are safer than abamectin products). Furthermore, sulfur-based fungicides can also be harmful to predatory mites, so avoid spraying these fungicides immediately before or after releasing any predators.”

Coastal Region

Rob Last reports, “Strawberries in the area are developing, albeit a little slowly. Typically we are looking at a growing degree figure of 240 GDD units. Covering for a month would be advisable to hit maximum yield. Pest and disease activity remains low. Brassica crops in the area look good, with some Alternaria lesions observed on the older leaves. Given the reduction in temperatures, we may begin to see some purpling of the older leaves. If the purpling occurs, it is due to the plants reducing phosphorous uptake. The purpling will grow out when temperatures increase without adding additional phosphorous. Remember to keep scouting through the holiday; early detection of pests and diseases will be beneficial.”

Zack Snipes reports, “I had a great time learning about citrus this weekend at the Southeast Citrus Expo in St. Helena. Based on the discussion, experience, and research, there is some potential for local citrus to be produced and sold in the coastal plains of SC. Fall crops are slow growing with the cold, cloudy days we can’t get rid of lately.  I am seeing higher incidences of leaf spot diseases in beets, lettuce, and other greens crops. I blame the humidity and tight spacing for this spread of disease. I saw some beets this past week with Cercospora leaf spot. Two varieties (red beets) were inundated with disease, while the third variety (golden beet) had less disease incidence. Taking notes on how varieties perform and adjusting for next season is a great disease management tactic. As we approach the season between Thanksgiving and Christmas, I want to remind everyone to get up your deer fences!!! This is when I see the most deer damage to strawberries. Strawberries are established, it’s cold, everyone is shopping for Christmas presents, and we forget that the deer are out and about looking for browsing material. If you don’t have a fence up, expect the deer to mow down your plants, causing significant yield reductions.”

Multiple varieties of citrus were brought in by commercial growers and backyard gardeners for the citrus judging at the SE Citrus Expo this past weekend.

Multiple varieties of citrus were brought in by commercial growers and backyard gardeners for the citrus judging at the SE Citrus Expo this past weekend.
Zack Snipes, ©2022, Clemson Extension

A golden beet variety has less disease incidence and severity in this field when compared to the red beets in the same row.

A golden beet variety has less disease incidence and severity in this field when compared to the red beets in the same row.
Zack Snipes, ©2022, Clemson Extension

Cercospora leaf spot on red beets.

Cercospora leaf spot on red beets.
Zack Snipes, ©2022, Clemson Extension


Justin Ballew reports, “We’ve had multiple nights of freezing temperatures and heavy frosts in the Midlands. Our fall cucurbits, tomatoes, and peppers are done. Growers spent some time harvesting what they could before the cold finished them off. Strawberries look good but haven’t done much since it’s turned cool. Brassicas are looking great. Thanksgiving is one of our biggest times of the year for brassica sales, so growers are going to be busy harvesting this week. Disease pressure has been very low, and insect pressure has been reasonable. This fall has been a great growing season.”


Andy Rollins reports, “Based on Dr. Jeremy Pattisons’ work on fall development in strawberries, we need to have between 600 growing degree days (GDD) (Chandler) and 800 GDD (Camarosa) from October-December. It is suspected that ‘RubyJune’ is closer to ‘Camarosa’ need-wise than ‘Chandler.’ To calculate GDD per day, add the daily high temperature to the daily low temperature and divide by 2 to give the average daily temperature. Next, subtract 50 from the average daily temp. to give your GDD for that day. Add up every day since planting. A grower near Rockhill has 285 GDD and still needs at least 315 GDD to hit the lower amount needed. It is doubtful that 600 GDD can be reached, as December is colder than October. To increase the accumulation of GDD, I recommended he cover now through mid-December. For many that planted late, this is critical to have a decent yield. PLEASE COVER (for 1 month). If you planted on time, this might not concern you. Just make sure you will be able to get to at least the 600 GDD mark.

  • Sample Calculation:
  • If today’s high is near 51 F and today’s low is 36 F: 51+36 = 87
  • 87/2 = 43.5 F avg daily temperature
  • 43.5 F avg daily temperature – 50 F base temp for strawberries = -6.5 GDD
  • Negative numbers count as 0 GDD
  • Add up each day’s GDD to give the total since planting
  • Total should be 600-800 GDD by December 31, 2022

Tom Bilbo reports, “While it is still early in the season, do not forget about regularly scouting for spider mites, especially if you are planning to cover your rows for an extended period. Spider mites are much easier to manage with either acaricides or predatory mites while populations are still low (<5 mites/leaflet (one-third of a strawberry leaf) pre-fruiting). Remember that spider mites usually first become apparent as ‘hot spots’ either at field edges or along dirt drive rows where they are protected from road dust.

If this document didn’t answer your questions, please contact HGIC at or 1-888-656-9988.

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