- Author: Neil McRoberts
General Situation Maximum temperatures over the coming week are forecast to be in the mid 90's F, which is ideal for thrips development. TSWV has now been reported in all areas of the Central Valley, with some relatively heavily infected crops in northern Kings County. Because of the relatively high disease pressure, a precautionary approach is recommended to avoid yield loss, particularly in late planted crops and varieties that do not carry the SW5 gene for TSWV resistance.
From now, through to the end of the cropping season, thrips generation peaks will be three to four weeks apart. Crops which do not carry the SW5 gene for TSWV resistance should be protected until fruit set is complete, bearing in mind that a new wave of thrips adults which can spread the virus will build up and decline roughly on a three to four week cycle.
Generation 3 was projected to peak on May 23rd and will have produced eggs and a new generation of larvae. Immediate spraying will reduce the number of these juveniles and reduce the numbers of adults in Generation 4.
Generation 4 is projected to peak on June 13th. Adults from this generation will already be appearing. Spraying between now will knock down the number of adults which are able to breed and lay the eggs which will give rise to generation 5. Because there is some TSWV present in the region generations 4 and 5 adults will contain infected adult thrips that will spread the virus. Concerted effort to reduce these generations will limit the effects of disease on late planted crops.
Generation 5 is projected to peak on July 4th. This may be the last generation of thrips for 2014 that can cause serious damage to processing tomato because most crops should be past the very sensitive stage by that time. However, generation 6 is projected to peak on July 22nd. Particularly on late planted and late developing crops, consider maintaining an active control program for thrips through to mid July.