Friday, July 23, 2010
Monday, July 19, 2010
Ethylene (C2H4) affects the growth, development and the senescence with all plants as well as tomatoes. It is present in all vegetables and fruits in small quantities as a natural hormone when the fruit or vegetable reaches a mature stage of development. Also, ethylene is used to initiate the ripening process with fruits and vegetables from an external source.
With tomatoes, the ripening process comes to a halt with temperatures above 85 degrees fahrenheit. When ethylene is not present at these high temperatures, tomatoes do not produce lycopene and carotene pigments responsible for color of ripe tomatoes depending on the cultivar. If ethylene were present the tomato would normally start at light green and go to red, pink, yellow or orange, again depending on the cultivar.
So often, we see tomatoes during the heat of July and August that are at full size called a "mature green" and sit on the vine until temperatures begin to cool down at summers end. At summers end all the tomatoes ripen at once. One other point would be the tomato will successfully stay on the vine unless, there are no other environmental stresses that occur in between the ripening stage.
Many fruits produce ethylene in larger quantities when exposed to external sources of ethylene. Some fruits and vegetables are sensitive to the ethylene and can dimish the quality of the produce and reduce the shelf life. Some of these are broccoli, cabbage, cauliflower, leafy greens and lettuce.Aside from the fruits and vegetables sensitive to ethylene, the following is a list of fruits which naturally produce ethylene: apples, avocados, bananas, melons, peaches, pears and tomatoes.
To learn more about ripening fruits and vegetables, go on-line and read The Ripener Newsletter.
Wednesday, July 14, 2010
Tomato psyllids are damaging to tomatoes and potatoes. Leaves on the tops of tomatoes yellow along the midveins and leaf edges. Leaf veins may turn purple. Growth stops while any new leaves remain small, narrow and stand upright producing a feathery appearance. Potato leaves become thickened and curled. Waxy beads of sugary waste from nymphs can be observed on the plants.
The nymphs are a flat yellow-orange discs about a 1/10 of an inch when full grown which sit on the leaves for up to 3 weeks. There can be between 3 to 4 generations of these psyllids in one season.
The damage begins while the nymphs are sitting on the leaves and feeding they are injecting saliva into the leaves which disrupts the plant growth. So leaf curling, color changes and slowed growth begins.
After the nymphs mature into adults after a few days they go from a pale color to gray or black with white bands and markings.
Where do tomato psyllids come from? Psyllids normally occur in southern states. They migrate to Colorado but they spend their winters in the extreme southwest of the United States and Mexico. Migration starts as the spring weather warms. These psyllids can become a pest in greenhouses with tomato and potato production.
Research trials from Colorado State University have found the most effective control comes when using sulfur. Other choices are permethrin/esfenvalerate rated with fair control.