A thrip……a tiny aphid like insect that you’ll likely never see even if you cross paths with it. They are a common agricultural pest with a variety of species that favor one crop or another. There are thrips found on cotton, wheat, tobacco, and peanuts just to name of few of the crops seen here in our region. The most common varieties in this area are the western flower thrip (Frankliniella occidentalis) and tobacco thrip (Frankliniella fusca). It is rare that a commercial row crop farmer would attempt to eradicate a thrip population once identified on the crop for two reasons. The thrip itself rarely causes enough damage to cause enough loss to a crop to outweigh the extra cost of purchasing the insecticide and applying it (diesel fuel, labor costs, time, etc). Second, it is extremely difficult to successfully apply insecticide as the insect burrows in the small crevices of a crop and lays its eggs within the plant’s tissue away from where any insecticide would reach. Unfortunately, thrips are the primary vector for the tomato spotted wilt virus (TSWV) which does cause significant crop damage particularly for gardeners and produce farmers like us.
Early in the spring planting season we noticed that the tomato and pepper seedlings were not flourishing. They were alive, but despite adequate watering and fertilizer they were wilted and stunted. We first saw it in the tomato plants. The leaf edges were curled while immature plants were beginning to flower and make fruit way earlier than they should. Uncertain of what was going on we took a wait and see approach. The peppers followed shortly after. The leaf curl was not as noticeable, but growth was stunted and they also began to flower and make early fruit. The fruit that the tomatoes and peppers did make was small and discolored early in the ripening process. When we showed the plants to a farming friend he immediately looked to the drying, neighboring, wheat field and came to conclusion we had a thrip problem.
A little bit of research taught us that the damage had been done and at this point there was little we could do to salvage our spring tomato and pepper crop. The thrips had thrived in the dry conditions we had early in the growing season. When the winter wheat crop that was planted next door began to dry, the thrips left that field looking for a new food source. Luckily for them and unluckily for us, the spring garden was planted during this time. The TSWV spread like wildfire down the rows of 144 tomato plants and 72 pepper plants. It has a wide array of plants it impacts and we are watching the other crops with our fingers crossed that they will be spared. Commonly infected plants that we have in the garden include potatoes and cucumbers. Our potatoes appear to have produced before succumbing to the virus though we have lost a portion of the cucumbers and all the zucchini. Watermelon is not one of the more commonly affected plants, but we are seeing curling of the leaves on our plants though they seem to be producing in a normal fashion thus far.
Plans for the fall garden include an attempt to replant tomatoes and peppers at a different site in hopes that we will be able to make up for lost production as well as prevent the virus from infecting the next planting. It is important that we plant away from the soil that is now infected by thrips and the TSMV to try prevent another infestation. Knowing what we know now we can treat early in the season for the thrip to prevent it from establishing on the plants or transferring over from any neighboring crops. This can be done by laying a granular insecticide down into the soil while the seedlings are being planted.
Thrips and TSWV have likely always been present to some degree on the farm, but the dry conditions and amble food source provided by the neighboring field created the perfect conditions for them to flourish and spread the tomato spotted wilt virus. Hopefully, with new knowledge and preparedness, we will be able to thwart their population in the fall and once again enjoy the typical spring bounty of tomatoes and peppers.
Learn more about thrips at: https://nc4h.ces.ncsu.edu/thrips-2/
Learn more about wheat thrips at: https://wheat.pw.usda.gov/ggpages/wheatpests.html#thrips
Learn more about TSWV at: https://rutherford.ces.ncsu.edu/tomatospottedwiltvirus/