Q&A with Jorge
Killing Spider Mites
I need to know about rotenone and pyrethrum sprays. What the hell is it with the spider mites? They seem to be getting worse. Under the microscope they are starting to look like Bush and Cheney!
Mr. Steven K., Internet
Looking at spider mites close up is definitely a scary thing! Avoid weapons of mass destruction! Pick the proper
Spider mite infestation is starting on the older leaves. Evidence of stippling (white spots where mites suck the life from foliage) is evident.
Rotenone is an extract of roots of several plants including Derris species, Lonchocarpusspecies, and Tephrosiaspecies. This poison is a Non-selective contact insecticide, stomach poison, and slow-acting nerve poison. Rotenone controls of beetles, caterpillars, flies, mosquitoes, thrips, weevils, and beneficial insects. They have to eat it to die. Rotenone does not kill spider mites.
Spot spray plants infested with spider mites. Aerosol sprays are most effective on spider mites. The spray is ice-cold when it exits the nozzle and if applied closer than 30 cm it can burn foliage. Aerosol spray contains a synergist, piperonylbutoxide (PBO) or MGK 264. Both are toxic to people. Pyrethrum dissipates within a few hours in the presence of air, HID light, and sunlight. Overcome this limitation by applying just before turning off the lights, the circulation, and vent fans for the night. One manufacturer, Whidmere®, offers encapsulated pyrethrum in aerosol form called Exclude®. As the spray fogs out of the nozzle, a bubble forms around each droplet of pyrethrum mist. The outside coating keeps the pyrethrum intact and extends its life for several days. When a pest touches the bubble, it bursts, releasing the pyrethrum. Liquid and wet table pyrethrum applied with a pump-type sprayer is difficult to apply under leaves where spider mites live.
I love this foto of spider mite webs enveloping an entire bud. The bud is dead and the spider mites skedaddled to the top of the bud. The good thing is they are easy to smash when together!
Spider mites will take over an entire weak bud if they have time. This greenhouse bud was in a dark corner and was overlooked for a couple of weeks.