Tomato Fruit Drop

by Gabriel
(Azerbijan)

Q. I have grown my tomato plants in the greenhouse, planting them during good weather. Then, temperatures dropped to 43 F for more then a month until heating system started to work. I applied fertilizer normally. Now, green fruit are dropping from plant. What can be the reason - is it effect of the cold weather? Will the next group of fruit be OK now that the temperatures are more consistent?
My second question: I found brown spots on the fruit (see picture). What can it be? Thank you.

A. We're so sorry about these problems. Hopefully this information will help you with your tomato plants.

• Fruit drop. Tomato fruit set and development is considerably affected by overnight temperatures. When temperatures are over 75 F or under 55 F at nighttime, fruit has difficulty setting and maturing. Next time, if overnight temperatures are forecast to be cold, consider using a space heater in the greenhouse. Fruit may also not set when plants are exposed to too much shade or are under-watered. In addition, check the fertilizer balance. Nitrogen (the first number in a fertilizer's three-number designation) promotes vegetative growth. Once plants flower and begin to set fruit, they need more phosphorus and potassium in order for tomatoes to be healthy and mature. (Learn more about fertilizing tomatoes.)
  
• Brown spots on tomatoes. Cold temperatures can also be the culprit here. Moreover, tomatoes grown in a greenhouse are susceptible to tomato spotted wilt virus (TSWV), which is transmitted by thrips. Other TSWV symptoms can include spotted or bronzed leaves, wilting on plants, stunted growth, deformed fruit, and streaked stems. Control thrips with yellow sticky traps.
  
  Good luck and happy gardening!
  Your friends at Tomato Dirt