ILLINOIS GIANT PUMPKIN GROWERS ASSOC.
- You may have them one year and then never again
- They are not a true insect, they are related to spiders ticks and scorpions
- Specialty miticides are usually needed
- They are small sometimes 1/50th of an inch
The Monsters in your garden
If Spider mite damage occurs on your pumpkin plants the most likely culprit will be the Two Spotted Spider Mite-Tetranychus urticae, not true insects, they are classed as a type of arachnid, relatives of spiders, ticks, and scorpions. Spreading almost worldwide they hitch rides and float alone the airstream finding new plants to feed upon. The Two-spotted, European red, Honey locust, Maple, and Oak spider mites flourish in hot dry conditions while the Southern red spider and Spruce mites do best in cooler weather.
Like many insects, the spider mite population can seemingly explode overnight, during winter they go into “diapause” a state of hibernation, this seems to occur when the day length reaches 13 hours per day, day length also wakens them in the spring. Warm conditions can bypass their need for diapause allowing him to stay active in homes and greenhouses regardless of the amount of light.
Identifying two-spotted spider mites
You may not know you have spider mites in tell you to see the damage to your plants, usually, it will appear as small chlorotic spots forming on the upper leaf surface they can be found on over 180 different plant species.
The two-spotted mite will be a slight transparent green, using a 10x magnifier will reveal two dark spots on their shoulders, these spots will disappear near the end of the season when their body color will change to a more solid red.
Their oval-shaped bodies have a usual size of 1/50 of an inch but can reach 1/20 of an inch with the female being the largest, hatching with 6 legs they will go through their first nymphal stage and then have 8 legs like the adults. Adults will have bristles on their legs and the females will usually have two dark areas one on each side, this area may be transparent enough to see internal organs. Though they can be seen with the naked eye placing a piece of white paper under the leaf and tapping it vigorously will knock some off the plant giving you easier identification. Males will usually have a pointed abdomen and the females will be rounded.
Exactly how the male overwinters I do not know but mated adult females overwinter on their host plants, tree bark and soil, most other species of mites overwinter as eggs in the soil. They become active in April/May with females able to produce 100 to 300 eggs that are attached to the underside of leaves with a fine silk thread, eggs have the appearance of fine water droplets, clear to slightly cloudy with a spherical shape. Hatching in 3 days with 6 legs they are now in their larval stage feeding for a few days then resting as they pass into the first nymphal stage with 8 legs. They pass through a second nymphal stage and then molt into adults. Hot weather increases the speed of this entire process down to as little as 5 days but can reach 20 days in cooler temps. The heaviest populations with multiple generations happen during July through Sept.If plant damage is severe females may float away on a silk thread to find new plants to infest, the lifespan of adult females is 2 to 4 weeks.
Look for signs of fine webbing mainly on the underside of leaves, all spider mites produce this webbing, mites may be under these webs feeding with their piercing-sucking mouthparts. They feed by piercing plant cells at a rate of 16 to 22 per minute and suck out the contents. White to pale spots will initially appear on the upper side of the leaf, these spots will die and may turn brown, as more damage occurs leaves may turn bronze color. yellowish or reddish and drop off. Damage will be more severe to drought-stressed plants, loss of leaves to watermelon, squash, and melons can cause a severe loss in yields. Plants heavily infested can be covered in webbing but at this point, the damage from feeding is too severe to overcome. try not to spread the mites on your clothing and tools to other parts of the property.
New plants brought onto the property is a common way for mites to spread, quarantine plants in tell they are fully examined.
Follow directions and your state and local laws when using insecticides, you may want to contact your local cooperative extension office to obtain a private applicator’s pesticide license they will teach you the proper application of chemicals and how to handle them safely.
If you plan to spray insecticides for other pests then this option is not for you in less you continually re-establish the predator species.
Many types of Predators can be used to control Spider Mite populations as long as they have a healthy environment to live in. Five types of predatory mites that are most commonly sold in the USA would include the Phytoseiulus persimilis, Amblyseius fallacis , Mesoseiulus longipes, Neoseiulus californicus, and Galendromus occidentalis. Most of these predators are nearly the same size as a two-spotted mite but they have longer legs allowing them to move faster than their prey, start by using approx 2000 for each 3000 sq ft of garden area.
Predatory insects include lady beetles six spotted thrips, lacewings that prefer the eggs, and immature larvae and there are several other types of insects to use. It is important to purchase the correct predator for your weather conditions, ask the supplier of help. The use of pesticides can actually encourage mite populations by killing of the beneficial insects that prey on them. The use of insecticidal soaps and oils can help control populations, these are often called “soft pesticides” some of these oils include Cottonseed and Neem oil. Plant extracts can be used clove and mint oils rosemary oil, cinnamon oil, also garlic extracts, insecticidal soaps are contact killers so full coverage of the plants is a must. Still, cautions need to be used when spraying, do not spray during direct sunlight or temperatures above 90F this can damage leaves and even kill plants. Dusty conditions encourage mites as does drought-stressed plants, blasting mites off of plants with plain water may be enough to keep the population within manageable numbers.
Regular insecticides rarely work on mites and can encourage their population by killing their natural enemies, and some insecticides that use the chemical carbaryl used in Seven have been shown to speed reproduction. Look for pesticides with the term MITICIDE those that state Mite Suppression is usually a weaker form of a Miticide. The best way for homeowners to get the strongest products. is to buy over the internet or from professional suppliers Usually labeled for Professional Use Only, they can still be used without a license. three applications may be needed at strict intervals to kill newly hatched mites read and follow directions for your product.
Active ingredients and their strength are what you want to look for, bifonazole, abamectin and hexythiazox have all been proven to work. Hexythiazox leaves a residue lasting up to 60 days and it also makes mite eggs sterile Aabamectin is probable the cheapest of the three, these products can be quite expensive but most will find that the smallest amount possible to purchase will last them several years, dosages are as low as 1/10 of an ounce to 1000 sq ft.