HOW TO CURB THRIPS THAT ARE HEAVILY ATTACKING MANY FARMS

Dudutech collaborates with Dow-Agro Science to enlighten growers on curbing thrip’s menace

Thrips are annually causing huge crop’s loses globally. Though a variety of chemicals and other management tools are available to growers, none is perfect in respect to expense and environmental safety against the changing thrips biotypes. To enlighten growers more on how to curb thrips havoc, Dudutech in collaboration with Dow-Agro Science organized a two day seminar at Enashipai resort in Naivasha and at Kongoni Camp in Nanyuki on 30th and 31st March 2017 respectively.
The event main speakers were Arturo Goldarazena, a professor and a thrips specialist from the Earth and Life Institute; Université Catholique de Louvain (Belgium) and Dr. Subbi of International Centre of Insects Physiology and Ecology (ICIPE).
According to Arturo, thrips are one of the most widespread, economically damaging and difficult pests to control worldwide. They cause damage to crops by piercing the cells of surface tissues and feeding on plants sap. This causes the cells to die leaving unsightly sunken white blotches on leaf surfaces. They also transmit deadly viruses such as Impatient Necrotic Spot Virus (INSV) and Tomato Spotted Virus (TSWV) that devastate numerous crop varieties.
“Thrips develop through a series of 6 stages in 2 to 4 weeks. They lay their eggs on leaves of the plants, flower and in soft tissues of stems. After the egg hatches, the thrips larva feed on the leaf commonly on the underside. They also feed on flowers and plant crevices,” Arturo explained.
Identification Of Thrips
Thrips can be identified by scouting and monitoring. This is a regular and systematic inspection of crops using detection tools such as sticky cards to identify insect pest, diseases, nutrient deficiencies and other problems. It is a cornerstone of effective IPM.
When scouting, farmers need to avoid wearing light colors especially yellow so that the insects are not attracted and carried on cloths from one area to the other. The less infested areas should be monitored first before heavily infested areas. Stock plants should also be examined before cutting to reduce the possibility of spreading the pests. According to the specialists, during cold months, plant inspections are more important than card counts.
Thrips are only visible at the adult stage. Growers thus need to develop an effective identification program, such as placing sticky traps to monitor the levels of population of thrips in a greenhouse. Using yellow sticky cards helps to detect adult thrips, whiteflies, fungus gnats, shore flies and leaf miners.
“A grower need to place 1 to 4 cards per 1000 square feet. Space cards equally throughout the greenhouse in a grid pattern, with additional cards placed near doorways and vents. Inspect cards each week; identify and count the insects. Record the information on a scouting form and replace the cards weekly to keep track on the population trend, “ Arturo opined
In addition, thrips are usually present in a crop before they are detected on sticky traps. The use of the pheromones traps in combination with the sticky traps allows the detection of thrips at an early stages. Pheromones also act to lure thrips from their shelters to the leaves thus increasing their exposure to natural enemies and to chemical crop protection products thus enabling a more efficient thrips control.
Biological Control
Biological control options are available, such as the use of Neoseiulus cucumeris, Hypoaspis miles, Orius insidious and Beauveria bassiana.
Neoseiulus cucumeris is a small predatory mite that feeds upon the small first instar thrips larvae and can also feed upon pollen. They are sold in bulk (mixed with wheat bran) or in sachets containing both the mites and grain mites as live prey.
Hypoaspis miles feeds on thrips pupae. Orius insidiosus, attacks all stages of thrips by sucking out their body fluids. Orius feeds upon pollen as well as spider mites and aphids. The insect pathogen, Beauveria bassiana, helps to suppress thrips populations. This bio-pesticide creates an infection as the fungal spores penetrate the host insect. Good coverage is needed to contact the thrips.
Chemical Control
Insecticides should be applied to adult thrips before they lay eggs. Several insecticide treatments are available at 3 to 5 days intervals; depending upon temperatures. The spray pump being used should be the one that produce very small-diameter spray droplets accessing growing points, flowers and other areas where thrips feed. It is necessary for a farmer to add surfactants to enhance the insecticide efficacy.
Rotation between classes of insecticides may help to delay the development of resistance to certain insecticides. “Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season. This helps to prevent development of resistance. For instance, organophosphates have a group number of 1B chemicals. 1B Group number should be alternated with chemicals that have a Group number other than 1B. Mode of action group numbers are assigned by IRAC (Insecticide Resistance Action Committee,” Professor Arturo taught the growers that had flocked the trainings.
Restricted entry interval (REI) should be adhered to, unless otherwise noted on the insecticide labels. REI is the number of hours from treatment until the treated area can be safely entered without protective clothing.
According to Oscar Shiliebo of Dow Agro-Sciences curbing of this thrips menace entails spraying twice per block. Some of the chemicals used are Evisect, Teppekki and tracer. Tracer he avers that should be used as the last resort after seeing a sign of resistance
Cultural Management Control
Weeds act as alternate host to thrips hence farmers need to eliminate them inside and outside the greenhouse. Crop rotation should also be adopted to prevent buildup of thrips.
Green house sanitation is another key control method of thrips, while covering of ventilation areas with nets to prevent thrips from entering the greenhouse is also an effective control method.
In his presentation Dr. Subbi of ICIPE recommended intercropping of crops with sunflower and maize, since this has shown a significant reduction of thrips infestation. This he said is revealed in a survey under the theme; ‘unraveling the diversity of thrips in the East African region’, that was carried out by ICIPE in over 250 locations in East African region.
“The survey highlighted that French beans are highly susceptible to thrips attack than any other crop. It also revealed that female thrips are highly prone to resistance than the males as they feed on broad spectrum of enzymes,” Dr. Subbi said.